1QwkSport2.5r

I've been under the assumption that the brass tube in the barrel is the "spraybar". But, I get what you're saying. I tried taking another picture to get a better look at the hole w/ slit and The one I posted is about as close as I can get with the lens on my camera. Basically, when looking at the disk/spraybar straight on, the slit appears to go all the way across the top of the tube with the round hole being almost in the middle of the slit. the slit goes through almost half of the tube when looking at it from the side.

I think I might have to look around for 2 mix disks.. I suppose without being able to look at them side-by-side in the flesh its gonna be pretty damn hard to tell them apart, I think.. Unless the slit on yours doesnt go all the way across the tube.

This probably doesnt help much, sorry..

madman75

From what I can tell from the picture and looking at mine, it looks like the slit on yours is wider than mine. I had to use a magnifying glass to see the slit or your camera does a great job at zooming in. Here's 2 pictures of mine. Not very good as I have a cheapo camera with no zoom. Hope this helps.

1QwkSport2.5r

They're too blurry for me to see.. that was a problem I had with mine being zoomed that close.. I would guess this is the problem - the idle orifice is too big. That would make sense being rough to transition. ......

1QwkSport2.5r

I wanted to post the reply I got from Mecoa about the carbs on these engines.

What I said: "Whats the price and difference on the two carbs you offer for the sportster .65? The two part numbers I see is 80-5801 and 80-5802. I'd like to keep the needle on the carb (80-5801). What is the reason these military engines with these particular carbs don't throttle well? Is it mismachined low speed disk or spraybar?"

The reply I got: "The military engines are NOT to be sold to the public. They would be considered stolen from the military. These were to be destroyed.

The only carb we sell is the remote needle version.

You can buy the mixture disk and try that. The part number is 85-5801"

I don't really want to do business with someone like this.. have others had similar experiences with him? I want to keep running these engines, but I don't want to have to get the parts from him based on the attitude he's given me.. Anyone have any suggestions? Anyone have any old sportsters laying around they dont want and would sell cheap?

Thanks fellas... I needed to vent a little bit.

NM2K

My Feedback: (14)

The man is telling you like it is. He isn't a polished salesman that will smooch your posterior to get you to buy something. I happen to like dealing with Randy. He doesn't fill your ears with plant food just to get on your good side. When I call, I want him to be strictly business - and he is.


Ed Cregger

1QwkSport2.5r

From my standpoint as prospective customer, I would expect the guy to be a little more helpful. I ask simple, short questions in hopes of resolving an issue and all I get is stuff like "you're not supposed to have that" or "it wont throttle well". I just want a little more explanation is all. I know he's a knowledgeable guy - I was hopeful he'd share a little more of that knowledge than he has thus far. Many people run his engines with great success and I would like to be one of those people. I don't want to be told "those engines are to be considered stolen from the military" when in reality they (the ones I have anyway) are not.

<shrug> It is what it is I guess..

madman75

I met the guy several years ago at the Toledo Weak Signals Show. I wanted to talk to him about K&B engines due to the fact he just acquired K&B. The guy was rude and not very friendly. I walked away saying I wouldn't have anything to do with his junk K&B engines anymore. Just didn't like his attitude. An older club member and I were talking about K&B the other day, he even mentioned about Randy's poor attitude without me even mentioning it. So, you're not the only one that sees it. I will never buy another K&B due to his p-$$ poor attitude.
I can see where you're coming from. You would like to know what the difference is so you could buy the correct part. I would say he won't say if it is what I suspect that K&B made some bad disc assemblies. This all took place before he owned K&B. He could at least tell you what part to replace without buying a whole new carb. So much for customer relations from Randy.
When he took over K&B, they were out of business as I far as I'm concerned.
Good luck solving your problem.
I'm curious as to how so many of the so called military engines made it out to the modeling public. Mine was found by a guy in a field where they used to shoot down the drones here in Ohio.
I found this link. I don't know if you have seen this but gives a little light on the subject.
http://www.mecoa.com/faq/carb/mixdisk/mixdisk.htm

1QwkSport2.5r

Oddly enough, I haven't seen that page before! I scoured that site for anything that would point me in the right direction since I haven't gotten any concrete info as to what the problem is. I did notice this picture:
My mix disk doesnt look like the one pictured - the small slit and the round hole are in the same spot, not seperate like the above picture. Is yours like the one pictured with two seperate holes? Also, does your carburetor have an idle stop screw? Both of mine DO have stop screws. Also, if your spraybar has two holes (slit and round hole) does your barrel have two holes as well, or just one like mine? If you can dig your engine out again and look since I can't get a good enough picture of mine, and let me know. (It sounds like yours might be a drone engine too based on your story?)

Also - I have seen a few sportsters for sale on the internet and many have pictures of the backplate - There is a stamping on mine (the only stamping on the engine) is "91" with little raised dots around it. Some of the engines I've seen for sale have the same marking, and some have "6" with less dots. If I were to buy a whole engine cheaply, is there a way of knowing if they are drone engines or not? One more thing I thought of. Is it possible if the idle RPM is too high (barrel opened too much) cause it to feed too much fuel at idle causing a rich transition? Obviously it would have to be feeding a ridiculous amount of fuel to cause this bad of a transition but it was a thought I had. Tach readings (with a Hobbico mini tach) at a warmed up idle is about 3500rpm - this seems high but the idle is a little more erratic at lower speeds. I did get it to idle down to 2200rpms after 2 quarts of fuel (1qt on the stand for break-in) but It would throttle up and clean out a little better with the idle higher.

I'm sorry this has turned into a giant discussion - I'm still new and learning the curve of the airplane world and would like to have a bit more fun. Its really frustrating trying to run this thing and have it quit on me in the middle of the pond and have to spend an hour casting a fishing line out hoping to snag the boat and bring it back or asking residents of the pond if I can go through their yard to cast from the other side of the pond to catch it. (The wind blew it across 3/4 of the pond opposite of where the public park is located where I was running from)

Madman75 - You have been very very helpful. I can't thank you enough for your time. Also, thanks to everyone else that has posted.. I know it sucks trying to help a rookie out, but I have nowhere else to turn to to get help. My LHS's (I have 3 airplane stores close to me) don't have a good common knowledge of how the K&B engines' carbs work or where to locate parts locally.

MJD

My Feedback: (1)

Nothing wrong with helping out rookies!

I'll bet after you put on some miles in the hobby you end up avoiding engine brands with caveats attached to them like "it runs great but you have to use 30% all castor fuel with an extra 2oz of Jagermiester per gallon and make sure it isn't the version with "666" on the left mounting lug and and break it in for 15 hours by the light of a crescent moon and it should run great".

1QwkSport2.5r

Well, the only reason I am trying to make these "turds" run is because I can't afford to go buy "good" engines. There are other engines out there that outperform the K&B's on a huge scale, but I got them free and they will work "good enough" until I can afford some good engines - I have my eye on a couple Jett's or Rossi's. I don't mind finicky break-in and adding extra castor to my fuel.. I just want the stupid thing to run and not quit in the middle of the pond... I guess the upside to stalling in the middle of the pond is getting good exercise running 1/2 a marathon to get around the lake to catch it..

proptop

My Feedback: (8)

What is the .65 Sportster's carb neck diameter?

It might be worth your while to post a "Wanted" in the RCU Marketplace for a different carb w/ the same neck dia.? Something with say a .300 to .350" venturi / throttle bore perhaps?

A "previously owned" O.S. or maybe Perry, etc. just might transform your engine.

I will look through my collection of stuff...can't promise anything, but...maybe?

1QwkSport2.5r

I looked up a perry carb already - I don't recall the dimensions of the inlet and outlet, but I do know it was a #4600 or #4606..I don't want to spend more than $20 per engine to have them running right. If I can't get it running right for that money, I would rather shelve them and find another engine to run. I just don't see it being worthwhile cost-wise. I don't remember for sure. I'll grab my vernier caliper and measure the dimensions and edit this post with those numbers.. I have to change the oil in the Wife's car before she leaves for work... (love the honey-do lists...)

I did swap spraybar/mix disk assemblies from the other new un-run engine and it didnt stall on me like it did before, but the transition was smokier (but more consistent at least). To the naked eye it appeared that the two spraybars for my two engines differ slightly in relation to the location of the round hole inside of the slit. Not a big variation but enough to notice it.

When pinching fuel off to shut the engine down it takes between 10 and 15 seconds for it to stall with the idle mixture as lean as the eccentric screw will go. This tells me the idle is in fact way too rich and is the cause of all of my problems, I believe. I also noticed air bubbles coming from the tank. I replaced all of the fuel lines a second time, used the tie-wraps that came with the new Sullivan 8oz tank I bought and got a good seal. with the fuel tank 1/2-3/4 full I still see a few tiny bubbles come through but not at all like I saw before. (brand new tank came with fuel line to connect clunk to brass tubes - new hose had holes in it.)

I was going to go run it again today sometime but I was going to mess with the carb a bit at home first. I noted a new RPM figure running the 13x5 - 10,850 - 200-300rpm rich from peaked out. That seems a bit fast for this size prop, don't you think?

Edit
Top of venturi diameter: .340"
buttom of venturi (crankshaft side): .343"
Outside diameter - bottom of carb: .623"
These figures are +/- .003" - My caliper is a cheapo digital unit from Asia somewhere.

Konrad

Your K&B by design is not a turd. Your specific engine might have unique issues.

Now I can still hear my father telling me these words of wisdom.

Stop throwing good money after bad!
There is little sense trying to make a silk purse out of a sow's ear
And stop trying to gold plate the trash heap!

I will say that ignoring his words of wisdom has given me great knowledge but at the high price of a lot of pain.

All the best,

Konrad

1QwkSport2.5r

Well, given the issues I've encountered with this engine, I refer to it as a turd though it is powerful in its own right. Once it is running as it should, I won't call it a turd anymore.

Believe me, I'm not trying to gold plate the trash heap. I'm really just shooting for bronze to be honest.. :B Kidding aside - Its not a race engine, this I know. It is a unique engine and requires a bit more finesse than others, this I know as well.. Just want the problem to go away so I can enjoy it. I love the way it sounds.

Konrad

It (the Sportster) was K&B's answer to the four cycle engine. A cheep 2 cycle set up to run as a four cycle. This is why it has such low power compared to the same size 2 cycle engine. But looked at as a four cycle it is great, it can spin large props quietly!

It was ported for low end torque. It had modest weight for its power output. And came with a super quiet muffler to go along with the four cycle philosophy. Now there was a management change at the time this came out (venture capitalist). These MBA changed the design by insisting that the piston be plated rather than the cylinder. This was done to save 5 cents on the cost of masking. If you take the time to look at most Sportsters you will see that the seal area around the crown of the piston is flaking (plating failure). This is because the plating has over heated as this narrow band of plating has to do all the sealing from the time the exhaust port closes to the time it opens. Had the cylinder been plated this seal load would have been distributed all along the upper cylinder. Also the thermal path would have be closer to optimum (for the plating
) as the cylinders is part of the heat exchangers (fins). There is no cylinder insert to interrupt the thermal path.

All the best,

Konrad

huck1199

I have all the Sporsters (20, 45, 65), several .61's, some 4011's, a .48,and a 1.00 Aero. I love them all. The Screaming .48 is perfect. I also like the made in USA factor. I have received excellent service when ordering parts. The Sportsters like 4oz of castor per gallon. I have learned how to tune and maintain an engine and have no problems.

Konrad

I didn't say there were any unusual problems. I just said that the K&B Sportster series is a low RPM two cycle engine designed to mimic the power of a four cycle engine. I did say that there is a manufacturing weak point that results in the plating on the piston (in the seal area) flaking. I did give reasons for the flaking and for plating the piston.

I really did like the K&B engine when they were run by folks that loved engine more than money. Because K&B went through many management teams it is often a crap shoot as to what kind of engine you get (the time line is often more important than the series).

The K&B 6.5cc and 7.5cc engine are some I still keep. And a Lee Custom PDP 61 is one to cherish. I think you can still get a Lee Custom.

All these Sportsters should have 20% to 25% oil content fuel and of that the oil should be 100% castor. Not for the corrosion protection needed in most other design but for the cooling and lubrication of the seal area on the piston.

All the best,

Konrad

huck1199

I didn't mean to imply you were critical of K&B.  I have seen so many guys  carp about K&B over the years and don't understand the bad reputation they have gotten.  I have been able to buy many K&B engines at bargain prices in auction sites because of the bad rep.  All the guys in my club are surprised at how well my engines run.  I just want to point out that there are alternatives to expensive OS engines. 

Konrad

I AGEE WHOLE HEARTILY!! With a cheer on the last point!

My mind is faded on this part but I think if the K&B box said a division of Aurora ...... it was a crap shoot. Now if the box said a division of Hobby,,,, it was a good engine with proper clearance. Can somebody give us a time line and the corporations that owned K&B.

All the best,

Konrad

blw

My Feedback: (3)

They are still available direct from Clarence Lee. You also get a price break from him over the same K&B items at Mecoa. I bought parts recently.

1QwkSport2.5r

I don't know if anyone caught my last post that I edited - Other than buying a new carb from K&B or a Perry carb, what other carbs might I find used that fit these specs:
Top of venturi diameter: .340"
buttom of venturi (crankshaft side): .343"
Outside diameter - bottom of carb: .623"
These figures are +/- .003" - My caliper is a cheapo digital unit from Asia somewhere.

If nothing else, I might hunt around for a complete engine if there's a way of weeding out the Drone engines from the normal consumer engines. There aren't many ways to tell them apart aside from the 1 stamping on the backplate. Mine has "91" with two raised bumps next to the numbers. I've seen 1 for sale with the same markings and I had seen 1 other engine that had a number 6 with more of the raised bumps/dots next to it/around it.

1QwkSport2.5r

I had another thought, and wanted a little input. I wanted to try just removing the eccentric screw and spring and put the idle disk back in. This would allow me to lean the idle a bit more (beyond what the eccentric screw can adjust to) and maybe clean it up enough. I know this would affect the high end a little bit, but I'm pretty sure I could compensate for this. I know there wouldnt be any mechanism to hold the idle disk in place since its just held in by 2 o-rings - To fix this I figured I could drill a small hole in the front of the carb housing and tap it to accept a small set screw which would go in just enough to hold the idle disk in place. (I would loctite the screw to seal the threads so it wouldnt have an air leak.

Think its worth trying? If I screwed it up or it didnt work it wouldnt matter too much because I'm probably gonna have to replace the carbs anyway.. I'm not sure if just an idle disk is going to fix it. OR if I can find a used carb..