Clarence Lee Modified K&B .61 engine
01-09-2007, 05:31 PM
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RE: Clarence Lee Modified K&B .61 engine
As to the rpm's of the K&B .61 engine.... We keep discussing the different K&B's.... Can anyone tell me what the rpm's would be on the stock K&B .61 with stock muffler? What would you gain if you went with the Perry pump and carburator model of K&B .61? What would you get with a Clarence Lee K&B (stock) .61.... Based on all using the same prop... 11 X 6 or similiar.... Thanks...
01-09-2007, 05:59 PM
#27
RE: Clarence Lee Modified K&B .61 engine
I have a CF Lee #6550 K&B 61. It is from the early 90's. It turns a 11-7 Top Flite wood prop at 13400 with the old square aluminum carb with the idle needle in the center of the throttle arm. Did about the same with a OEM Perry for a 61. (I did have 4 of them). I tried the same engine with the K&B pump back plate and a new Perry pumper carb for the K&B 61 and it turned about the same rpm. Maybe 13500?
01-09-2007, 07:46 PM
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RE: Clarence Lee Modified K&B .61 engine
Thanks for the reply... I have one and am helping a friend who is a new pilot with his K&B 61... both with Perry Pump and Carb... one is turning 11,000 and one is turning 11,500... both using 11 x 6 prop... What do we need to do so that we can get more rpm's and stay with the stock muffler and a standard generic 11 X 6? Thanks Richard
01-09-2007, 09:23 PM
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RE: Clarence Lee Modified K&B .61 engine
Richard, what brand of 11x6 are you using?
Lots of guys use the APC 11x6 as a load yardstick with .46 and .50 sized engines. A good .46 will pull about 12-12.5K and a good .50 or .52 will pull low thirteens.
Lots of guys use the APC 11x6 as a load yardstick with .46 and .50 sized engines. A good .46 will pull about 12-12.5K and a good .50 or .52 will pull low thirteens.
01-09-2007, 09:54 PM
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RE: Clarence Lee Modified K&B .61 engine
Thanks for all the info. I think before I go out and purchase a tower .75 I will try a pipe on the K&B .61 and see what RPM's I get. If I can get 13,500 to 14,500 out of the engine--I might stick with the K&B. The lightness of the K&B would make it more desireable.
01-10-2007, 02:27 PM
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RE: Clarence Lee Modified K&B .61 engine
I checked the Perry web site as posted here and found that the pictures show a totally different pump and carburator..... I must have an older system... The pump is built in to the back plate and the carburator has an adjustment screw over the fuel inlet....
01-11-2007, 02:04 AM
#33
RE: Clarence Lee Modified K&B .61 engine
The Clarence Lee K&B .61 is an outstanding engine. Its performance is similar to the newer Twister. DO NOT EVER run the engine at over 13,000 rpm or you will risk breaking the crank journal off as it is only a pressed in fit. The engine has a considerable amount of torque and will swing the larger props faster than the current high performance engines that require high rpm to reach their horsepower rating.
The K&B .61 reaches max HP at 12,000 rpm. If you want to run higher rpm, buy the one-piece forged crank used in the Twister. You will also need to buy a new rod to match the crank. Higher rpm will no longer be a problem.
The issue with noise is because Clarence opens up the outlet on the stock muffler to make it less restrictive. However, the engine reacts very nicely to a tuned pipe and larger carb. I ran a Mac's Wizard mini pipe and Perry carb from a K&B .45 ducted fan engine. The engine really performed. I previously pylon raced a World .40 size Mustang ARF with a Lee .61 in the SWRA. I would get great pleasure beating the hot shots with their current expensive engines with my 1950 era designed Lee .61.
Good Luck,
The K&B .61 reaches max HP at 12,000 rpm. If you want to run higher rpm, buy the one-piece forged crank used in the Twister. You will also need to buy a new rod to match the crank. Higher rpm will no longer be a problem.
The issue with noise is because Clarence opens up the outlet on the stock muffler to make it less restrictive. However, the engine reacts very nicely to a tuned pipe and larger carb. I ran a Mac's Wizard mini pipe and Perry carb from a K&B .45 ducted fan engine. The engine really performed. I previously pylon raced a World .40 size Mustang ARF with a Lee .61 in the SWRA. I would get great pleasure beating the hot shots with their current expensive engines with my 1950 era designed Lee .61.
Good Luck,
01-11-2007, 01:52 PM
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RE: Clarence Lee Modified K&B .61 engine
Thanks Mike,
Good information that I was looking for! I want to use this for speed so I will look into replacing the crank and rod. What pipe and prop would you suggest?
Good information that I was looking for! I want to use this for speed so I will look into replacing the crank and rod. What pipe and prop would you suggest?
01-11-2007, 05:04 PM
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RE: Clarence Lee Modified K&B .61 engine
I also saw in the K&B parts list a counter-rotating crank. Is changing the crank to a counter-rotating crank all that is needed for the engine to run backwards? The Bobcat is a pusher plane and the engine running backwards would open up a vast aray of props not available locally.
If this will make the engine run backwards will it have the same power? Is there any down side to doing this?
Thanks
If this will make the engine run backwards will it have the same power? Is there any down side to doing this?
Thanks
02-17-2007, 06:53 PM
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RE: Clarence Lee Modified K&B .61 engine
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the internet so it is easy to understand your confusion.
To start with, the engin I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stok 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crankpin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or owrn out. I rebush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the internet so it is easy to understand your confusion.
To start with, the engin I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stok 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crankpin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or owrn out. I rebush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
02-17-2007, 07:50 PM
#39
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RE: Clarence Lee Modified K&B .61 engine
I bought 4 Lee Custom .40 pylon engines from him back in the mid-80's. They ran well, and he supported them after the sale. For those with a really long memory, he used to build racing engines for Bob Smith back when he was cleaning everybody's clock in Formula One in the 70's.
02-18-2007, 04:58 AM
#40
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RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: Larry Legg
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
Larry,
That is a great explanation by the GURU Clarence Lee!
I had the pleasure of 'E-speaking' with him several years ago, first about my peeling OS.40FP and later about the definition of over-square and under-square engines...
Great guy and engine builder/designer.
About crank-pin clearance numbers...
It seems current engines have a lot more 'oil-clearance' there than engines of two-three decades ago.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
The K&B #6550 and Twister; unlike the HB .61 that began as 'sort-of' its clone, utilizes a one-piece crankcase. Assembly and disassembly of the con-rod bottom end, will not be as easy with the Clarence Lee modified con-rod, as it is/was with the OEM item.
03-06-2007, 06:27 PM
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RE: Clarence Lee Modified K&B .61 engine
I just got around to tuning this engine on a 10cc pipe. Following Clarence Lee and K&B method of tuning I was able to get 15,800 out of the engine. That is with a 10 x 7 prop. I will be flying a 10 x 8 prop so on the ground rpm should be about 14,800-15,000 with 15,800 when unloaded in the air. Not too bad.
03-21-2009, 02:12 PM
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RE: Clarence Lee Modified K&B .61 engine
Maybe this is old news, but I noticed that Clarence is blogging about engines on the MAN website:
http://blogs-modelairplanenews.com/p.../EngineClinic/
Tom
http://blogs-modelairplanenews.com/p.../EngineClinic/
Tom
03-21-2009, 07:06 PM
#43
RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: DarZeelon
Larry,
That is a great explanation by the GURU Clarence Lee!
I had the pleasure of 'E-speaking' with him several years ago, first about my peeling OS.40FP and later about the definition of over-square and under-square engines...
Great guy and engine builder/designer.
About crank-pin clearance numbers...
It seems current engines have a lot more 'oil-clearance' there than engines of two-three decades ago.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
The K&B #6550 and Twister; unlike the HB .61 that began as 'sort-of' its clone, utilizes a one-piece crankcase. Assembly and disassembly of the con-rod bottom end, will not be as easy with the Clarence Lee modified con-rod, as it is/was with the OEM item.
ORIGINAL: Larry Legg
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
Larry,
That is a great explanation by the GURU Clarence Lee!
I had the pleasure of 'E-speaking' with him several years ago, first about my peeling OS.40FP and later about the definition of over-square and under-square engines...
Great guy and engine builder/designer.
About crank-pin clearance numbers...
It seems current engines have a lot more 'oil-clearance' there than engines of two-three decades ago.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
The K&B #6550 and Twister; unlike the HB .61 that began as 'sort-of' its clone, utilizes a one-piece crankcase. Assembly and disassembly of the con-rod bottom end, will not be as easy with the Clarence Lee modified con-rod, as it is/was with the OEM item.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
03-22-2009, 01:41 AM
#44
Senior Member
RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: Broken Wings
Clarence just stated "I re-bush the rod for .002" clearance"..... The SAME rod fits and goes together in the SAME engine the SAME way as a rod with .004" clearance.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
ORIGINAL: DarZeelon
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
Tom had revived this thread, after it was 'dead' for over two years... I had to think to recollect why you were quoting me...[
]As to that statement; please see the brown shaded lines in the quote above.
In all two-stroke engines, when running normally; and even when being run rich (four-cycling warm, as in a C/L stunt engine), the con-rod is always under compression.
Unlike a four-stroke engine, that needs the piston to be stopped at and pulled down from TDC, at the end of the exhaust period and the first part of the intake period; a two-stroke engine always applies down force on the piston.
So, it would seem the bottom half of the con-rod's bottom-end, is not needed for a two-stroke engine to keep running...
Even if the oil clearance is rather large, nothing bad will happen and the (one-piece crankcase) engine would be easier to take apart and reassemble.
Clarence Lee obviously prefers a smaller oil-clearance and has enough credentials to prove that it works...
A two-part crankcase K&B would not mind, it seems.
Dub Jett thinks otherwise, if his One-piece crankcase engines are truly set up with such a large oil-clearance; and he also has enough credentials to prove that it works...
I never examined this attribute in a Jett.
03-22-2009, 04:14 AM
#45
Senior Member
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RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: Broken Wings
Dar, Clarence just stated "I re-bush the rod for .002" clearance"..... The SAME rod fits and goes together in the SAME engine the SAME way as a rod with .004" clearance.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
Could Clearance be an apostle of Gordon Jennings or vice versa. Personally, I don't think these aftermarket producers of "tuned pipes", read "expansion chambers", know their rectums form a tin dipper, and they couldn't find their butts with both hands with the lights on.
Just shoot me. Bring it ON, Mo' Frere.
Bill
ORIGINAL: DarZeelon
Larry,
That is a great explanation by the GURU Clarence Lee!
I had the pleasure of 'E-speaking' with him several years ago, first about my peeling OS.40FP and later about the definition of over-square and under-square engines...
Great guy and engine builder/designer.
About crank-pin clearance numbers...
It seems current engines have a lot more 'oil-clearance' there than engines of two-three decades ago.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
The K&B #6550 and Twister; unlike the HB .61 that began as 'sort-of' its clone, utilizes a one-piece crankcase. Assembly and disassembly of the con-rod bottom end, will not be as easy with the Clarence Lee modified con-rod, as it is/was with the OEM item.
ORIGINAL: Larry Legg
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
I took a friends advice and went to the source (Clarence Lee) about the Modified K&B .61 ringed engine I bought from him.
I got a response back from Clarence Lee about the K&B .61 he sold in a week. It sounds like it will work for me and perform better than I expected. These are the facts about the engine he modifies. Below is his response.
You have been getting a lot of misinformation off the Internet so it is easy to understand your confusion.
To start with, the engine I sent you will turn just as strong if not stronger than the "Twister" 61. If a Twister and older stock 61 are compared, the Twister will have an edge. However, this edge comes through the semi-Schnuerle porting and a larger carburetor intake. The Twister is not a true Schnuele scavenged engines as it only has one mixture transfer channel. The Twister uses the same case as the ringed 61 with notches cut at the top edges of the bypass channel and two extra holes drilled in the sleeve. I do the same thing when incorporating PDP in the engines I sell, except I mill slots at the top of the bypass and in the sleeve. In effect, both engines utilize the same type of porting. Sort of a combination of semi-Schnuerle and PDP. The engine I sent you also uses the Twister carburetor, crankshaft, and rod. The stock rods have far too much crank-pin clearance (.004-.005") that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. I re-bush the rod for.002" clearance, so do not ever replace the rod. Also, I have modified the timing in your engine for higher rpm operation and pipe use. Didn't you read the letter that accompanied your engine?? Bear in mind that the engines you mention as possible alter native choices are not intended for higher rpm operation. The only two engines that I can think of, off hand, that would give you more speed would be a piped Rossi 61 or OPS 60 (if you could find one). And even then, the small increase in speed might not justify the cost of these engines.
There is no reason to install a counter-rotating crankshaft in the engine. Both APC and Zinger as well as Graupner and others make "pusher props". Install a 10 x 8 APC prop, 25-30% nitro fuel, and you will have plenty of speed. With this combination you should see in excess of 14,000 rpm on the ground with the pipe the proper length. Start with the pipe length about 12: from the piston face to start off the maximum dia. pipe section and shorten in 3/8" increments. When the rpm falls off, pull the pipe back out 3/8" and insert the cut off section back in the rubber coupler.
I would appreciate hearing what kind of speed you do see.
Larry,
That is a great explanation by the GURU Clarence Lee!
I had the pleasure of 'E-speaking' with him several years ago, first about my peeling OS.40FP and later about the definition of over-square and under-square engines...
Great guy and engine builder/designer.
About crank-pin clearance numbers...
It seems current engines have a lot more 'oil-clearance' there than engines of two-three decades ago.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
The K&B #6550 and Twister; unlike the HB .61 that began as 'sort-of' its clone, utilizes a one-piece crankcase. Assembly and disassembly of the con-rod bottom end, will not be as easy with the Clarence Lee modified con-rod, as it is/was with the OEM item.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
Could Clearance be an apostle of Gordon Jennings or vice versa. Personally, I don't think these aftermarket producers of "tuned pipes", read "expansion chambers", know their rectums form a tin dipper, and they couldn't find their butts with both hands with the lights on.
Just shoot me. Bring it ON, Mo' Frere.
Bill
03-22-2009, 08:03 AM
#46
RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: DarZeelon
BW,
Tom had revived this thread, after it was 'dead' for over two years... I had to think to recollect why you were quoting me...[]
As to that statement; please see the brown shaded lines in the quote above.
In all two-stroke engines, when running normally; and even when being run rich (four-cycling warm, as in a C/L stunt engine), the con-rod is always under compression.
Unlike a four-stroke engine, that needs the piston to be stopped at and pulled down from TDC, at the end of the exhaust period and the first part of the intake period; a two-stroke engine always applies down force on the piston.
So, it would seem the bottom half of the con-rod's bottom-end, is not needed for a two-stroke engine to keep running...
Even if the oil clearance is rather large, nothing bad will happen and the (one-piece crankcase) engine would be easier to take apart and reassemble.
Clarence Lee obviously prefers a smaller oil-clearance and has enough credentials to prove that it works...
A two-part crankcase K&B would not mind, it seems.
Dub Jett thinks otherwise, if his One-piece crankcase engines are truly set up with such a large oil-clearance; and he also has enough credentials to prove that it works...
I never examined this attribute in a Jett.
ORIGINAL: Broken Wings
Clarence just stated "I re-bush the rod for .002" clearance"..... The SAME rod fits and goes together in the SAME engine the SAME way as a rod with .004" clearance.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
ORIGINAL: DarZeelon
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
What makes YOU think that 'oil-clearance' actually isn't......???
As you know, (from the Jett web-site) "Jett rods have about .003-. 004 (.07-. 1mm) rod-to-crankshaft clearance. This is approximately twice that of an O.S. This is why you see the extra motion. This is not a problem and here is why: During high-speed operation the engine loads the rod in one direction only—the piston pushing down on the crankshaft. This means that the rod is almost always touching at the top of the shaft, leaving a gap at the bottom. The gap is where the lubricant is stored and the more the better. During idle, you may hear the click of the rod moving back and forth on the shaft. The loads are very low at this speed and do not cause a problem.
We have measured rods after years of hard use and find the wear almost zero. In fact, we often say, “rods don’t wear”. Years of pounding are more likely to fatigue the rod body itself, and for this reason it is reasonable to replace them every few years. In racing, once a year would not be unreasonable. Always replace your rod after a shaft run (no propeller).
Finally, do not measure rod play at top dead center. This magnifies the clearance. Place the piston about one-half way between the top of the exhaust and top dead center. You will find a big difference. " end quote.
Just curious...
Tom had revived this thread, after it was 'dead' for over two years... I had to think to recollect why you were quoting me...[
]As to that statement; please see the brown shaded lines in the quote above.
In all two-stroke engines, when running normally; and even when being run rich (four-cycling warm, as in a C/L stunt engine), the con-rod is always under compression.
Unlike a four-stroke engine, that needs the piston to be stopped at and pulled down from TDC, at the end of the exhaust period and the first part of the intake period; a two-stroke engine always applies down force on the piston.
So, it would seem the bottom half of the con-rod's bottom-end, is not needed for a two-stroke engine to keep running...
Even if the oil clearance is rather large, nothing bad will happen and the (one-piece crankcase) engine would be easier to take apart and reassemble.
Clarence Lee obviously prefers a smaller oil-clearance and has enough credentials to prove that it works...
A two-part crankcase K&B would not mind, it seems.
Dub Jett thinks otherwise, if his One-piece crankcase engines are truly set up with such a large oil-clearance; and he also has enough credentials to prove that it works...
I never examined this attribute in a Jett.
03-22-2009, 08:27 AM
#47
Senior Member
RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: Broken Wings
You believe that the extra connecting rod clearance was designed to ease the assembly of the engines? I think the K&B .61 a one-piece case as well?
You believe that the extra connecting rod clearance was designed to ease the assembly of the engines? I think the K&B .61 a one-piece case as well?
I was visualizing the #6550 as a 'bigger brother' of the #4011, which does have a separate front crankcase...
It apparently does not.
Even the HB .61 engine, which was at a time considered to be a 'K&B clone'; and has a two-part crankcase, no longer resembles it...[sm=spinnyeyes.gif]
My mistake; even though a larger bottom-end clearance definitely eases its hooking and unhooking on/from the crank-pin...
So, we are left with Clarence Lee that says to make the oil-clearance small, Vs. Dub Jett that says to make it large...
03-22-2009, 10:06 AM
#49
RE: Clarence Lee Modified K&B .61 engine
ORIGINAL: DarZeelon
As to that statement; please see the brown shaded lines in the quote above.
ORIGINAL: DarZeelon
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
I suspect this increased 'oil-clearance', actually isn't...
Many engines produced then had a two-part crankcase, that enabled the crank-pin to be inserted straight into the con-rod bottom end, or had the blanked hole in the back of the crankcase (Webra .40?), to enable removal and insertion the wrist-pin, to enable assembly/disassembly.
Current engines have a unified crankcase that forces a need to hook the con-rod onto the crank-pin at an angle; askew, if you will (after sliding all the way in, it ends up straight).
This makes it necessary for the hole at the bottom to be larger than is necessary for the oil clearance.
.Do you honestly think a designer couldn't figure out another way to get the movement necessary to fit/remove a conrod other than boring out the rod bush larger than they might like to have? Off the top of my head I can think of at least three different ways or even a combination of all three. As for the difference in thoughts between the K&B and Jett clearances, the Jett is designed for much higher revs so I'd suspect Dub preferred a larger clearance.
03-22-2009, 10:22 AM
#50
RE: Clarence Lee Modified K&B .61 engine
Apparently K&B thinks so as well. Clarence re-bush's them to .002 to eliminate the "Clicking".
"The stock rods have far too much crank-pin clearance (.004-.005" that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. "
It's interesting...[8D]
"The stock rods have far too much crank-pin clearance (.004-.005" that results in clicking when turning the engine over and fellows thinking the rod is defective or worn out. "
It's interesting...[8D]