I would still like to know how they faired with an 11-7.

I think it's a 6550 plasticmaster. The muffler looks different and it has a non-remote needle valve but the engine looks like a 6550. I don't know K&B engines very well.
Sport Pilot, I just noticed on the K&B website that the recommended prop for the 6550 is an 11x7.

Tim:

Your engine is either a 6330 or a 6550. It does have the "Block" carb, supplied in production between the ones that came with the Perry carb, and the current ones with the "Ribbed" carb.

The only way to tell the 63xx from the 65xx is the prop drive washer. The 63xx had a flat in the crank mating with a cast drive washer, the 65xx uses a plain round crank, a centering cone, and a fully machined drive washer.

There's no great amount of "Stuffing' of the case betwen the early and late production, but the early engines were slightly smaller inside. The late backplate wont fit the early case.

Bill.

Thanks for the info Tim C .... good stuff.

turbo

Here's the result of the old baffle piston .61 and an APC 11x7. I don't know how close the load is between an 11x7 and 12x6 APC, but it seemed to like the 11x7 better. It peaked out at 11,760.
Bill, thanks for the info. My prop drive washer is machined and will not pull off by hand. My engine must be the 6550. Does anyone know what horsepower it takes to turn an 11x7 @ 11,760? Is altitude considered when computing horsepower?

Tim:

According to the power and thrust spread sheet I got from Pe Rievers the 11x7 APC at 11,760 rpm takes 1.03 hp, and gives 6.2 pounds thrust.

And yes, the 6550 drive washer tends to stick in place, the older cast one would fall in the grass when changing a prop.

Bill.

The best prop I ever found for the K&B .61 is the 11-7 1/2 Master Airscrew.
I believe a 11-7 1/2 Zinger would work quite well too. You can tell the difference
with the 11-7, 11-7 1/2, the 11-8, and the 12-6. I never tached one though.

FBD.

A 12-6, or a 12-7 APC prop will "dog down" a 6550 K&B into a pathetic
state of performance....if you wanted to call it that.

FBD.

An 11x7 and 12x6 are pretty much equal. The 12 will pull better and the 11 will give more speed.

I have a Tower.75 expansion type muffler which fits up to the K&B 6550 with just a little modification of the holes. Don't like the stock muffler because stinger points straight back and don't want to fuss with an exhaust deflector if it can be avoided. Has anyone ever tried using the Tower or other muffler on the 6550 engine? Results ?

Blue Skies, Green Lights !

Thought you might be interested in the following:-
Several years ago I was getting ready to replace one of my KB 61's which was getting a bit "doggy" after over 10 years of hard use when I discovered a new piston and ring (dykes) I had in my parts box from a Merco 61 fit the liner almost perfect! With a bit of enlarging and squaring of the bypass ports to line them up, and some dremel work on the head to clear the piston baffle, I soon had a KB/Merco 61 ready to run! And run it did - and extremely well! I flew it in my "Redbird" Bipe
( see http://www.quiknet.com/~pheller ) and it certainly outperformed the original KB, even when it was new! I mentioned it to C. Lee whose only comment was My original KB must have been a dog! Interesting since he designed the Veco 61 originally with a dykes ring!

Phil

K&B .61 owners,

I just bought a never been flown Carl Goldberg Super Chipmunk that was built 15 years ago with a never been run K&B .61 (6550 model) with a Tatone muffler. I went to my local hobby store and was recommended to use a 12x6 APC prop. Break in involved running on the rich side with 1 tank of 10% castor synth blend and 1 tank of 15% all synthetic. The APC 12x6 flight and wooden 11x7.5 flight were noticably different.

Thank you all for this thread and what it has done for my K&B .61. I was NOT a happy camper until I changed to the wood 11x7.5. I will surely be trying the master air screw brand as well as the APC in that 11x7.5 size if I can find them.

root

I'll bet the 12-6 APC prop dogged the K&B down big time, huh ?

FBD.

FBD,

NNNoticably DOGGED to a point where I was wondering if the K&B was the wrong choice!! When I changed to the 11x7.5 -- the guys at the field (to my pleasant surprise) said the Chipmunk was not flying "scale" cause it was "way too fast" !!!

And "way too fast" is with the engine still running rich with a fast idle and only a gallon of fuel thru it.

root

The 11-7 1/2 MAS prop is the best prop I've found for the K&B .61's
after over 30 years of flying them.

For some reason, most people think the APC props are great, much better
than the Master Airscrews....I don't know why....[sm=stupid.gif]

I just gave away all my APC props, about 15 or so.

FBD.

Hey Dave,

I can't help but trying and comparing the APC 11x7 (they don't make a 7.5) and the MAS 11x7.5 versus the 11x7.5 Zinger.

I'll let everyone know the results as far as RPM's on the ground as soon as I can get a hold of the props.

I might need the ounce or so's extra weight of the APC because my Super Chipmunk was built really light but it's still a teeny bit tail heavy -- I haven't exactly weighed her yet but I'm sure she's no more than 6.5 lbs All Up Weight (soakin' wet)

Have you compared the APC 11x7 to the MAS 11x7.5?

An earlier statement in this thread was: "According to the power and thrust spread sheet I got from Pe Rievers the 11x7 APC at 11,760 rpm takes 1.03 hp, and gives 6.2 pounds thrust. "

The K&B specs say that the .61 is supposed to be 1.3 HP

What do you think of those apples??

Maybe the MAS 11x7.5 prop can produce the difference of 1.03HP and 1.3HP????

root

root, those were my rpm numbers taken on a hot day at 4000' elevation with an old 6550 given to me used with who knows how many hours on it. I'm betting yours will do a lot better.

TimC,

I thought those numbers were a little "off" seeing as how I was getting readings in the low eleven hundreds with the APC 12x6 on the 1st tank, 90 degree day, running 10% castor/synth before I richened it up and lowered the rpms to high 9's.

K&B 61 owners,

I'm still having trouble getting a low idle - the low end screw is 'out' past the 'level with the barrel" factory setting.

I heard it takes 2 gallons before you can really get the lowest idle and full throttle with no transitionproblems.

I'm excited about the potential that my flying buddies tell me to expect once the engine is broken in.

ACCORDING TO THE DIRECTIONS FROM THE BOX, As I lean out the high end, I should be richening (turning counterclock) the low end -correct??

Are there any tips anyone can give me as far as the time/tankfuls expected before the process is complete? I'm at about 1 gallon of 15% synthetic so far.....

root

I like to use old engines and people accuse me of being cheap but from my point of view, if I have them around and don’t use them, they would just collect dust. About a month ago, I took a new (from about 1972) Veco .61 out of the box and bolted it to a GP 58�/.46 size Extra. It replaced an old, lightly used HP 61 (4-bolt) and after about a gallon of 10% fuel, the Veco is faster and revs higher than the HP. I’m now using 15% nitro.

Vertical performance is very good and the model will lift off on it’s own after a 10-15 foot run. I’ve tried an APC 12x6 and APC 11x7-and I have an 11x8 APC on order. The 11x7 revs higher but the 12x6 is faster in the air so I can’t see how a 12x6 prop bogs this engine down–it’s turning 12k on the ground. I’m an APC snob but after reading this thread, I’ll try some wood props that I have (11x 7, 7-/12, 7-3/4 and 12x6 Rev-Ups). I might even have the 12x7.5 MAS.

The low-end setting on the Perry carb is very critical but after finding the right spot, there’s no hesitation to full throttle The Veco engine has become very reliable and I like the throaty sound of the flow-through muffler. Sure it’s a little loud but the sound is more like a Pitts and not a annoying as most sport mufflers. It’s been said that the new .46 engines offer about the same performance as the old .61s and I believe this is true to a point but I’m pretty familiar with them and none of the .46 powered sport planes at our field have smoked the Veco and this one will pull away from most of them. Not bad for an antique.

[X(]....[X(]....[X(]....you should be running a fuel with castor oil in it....

....ringed engines love castor....I wouldn't run my engines without castor.

FBD.

Is anybody else besides me running non-castor fuel thru the K&B 61?

I just can't stand the burnt deposits from the castor.

What would you do to prevent the yukky build up when the engine is surrounded by the cowl and my tatone muffler isn't the tightest fitting / non leaking muffler.

Does anyone out there using the all synthetic stuff having any troubles compared to the castor users?????

root

p.s. got a 11x7 APC to try / compare w/ the wooden 11x7.5--- the Master air screw 11x7.5 is next on the list......

---------------------


The .40s were also sold with Irvine carbs for a while. They were nice. Made of grey plastic. I don't know if the larger engine ever had the Irvine carb.

The earliest K&B .61s revved their brains out, compared to those made later. It always puzzled me why K&B changed their engine from an absolute winner to a ho-hum also ran. I have owned several of both fast and ho-hum versions, but never took the time to analyze the differences.

--------------------


If your engine uses a connecting rod with bushings on both ends, you'll be fine using all synthetic oil fuel as long as you keep the mixture a tad rich. This means that some of the early Chinese engines and smaller old Fox engines will self-destruct on this fuel in a very short time. In fact, some of the K&B .40s used rods without an upper bushing in the wrist pin area and they too would suffer premature failure. The later 8011 version came out with a double bushed connecting rod that did not suffer this fate. The K&B .61 Series 75 was doubled bushed for sure.

In my older age, I've dropped back to using fuel with a bit of castor oil in it. I'm not in a hurry to go anywhere anyway, so the extra clean up time is worth the satisfaction of knowing that my engines might last a few more flights should the worst happen and the mixture goes lean during flight.

You might look into trying a BME G90 gas engine, if you really don't want to deal with a lot of mess on the model with an enclosed engine. I have one sitting here NIB (no, not for sale) that I can't wait to get running this Fall, after it cools down a bit.

Have you guys ever heard of a Bru-Line fine mesh air filter (BRU-202 from Horizon) to keep the carb "spray" down in the carb?

It sits on, in & around the venturi.

Anyways, could it be that I'm having trouble with the low end (only a reliable 2800 rpm) because of not using a idle bar glow plug?

I'm using a OS#8.

root

The air cleaner will work fine, and keep a lot of the carb mist off the engine.

You do not need, nor will it help to use an idle bar plug in that engine. Use
a K&B 1L plug in it.

You can seal the exhaust manifold to the engine with some high temp
silicon seal, and that will keep the engine cleaner as well.
FBD.