I have a older K&B 61 that has a tendency to heat up. Doesn't seem to make any difference on how rich it is (other then it runs horible when it is too rich). It has a tendency to quit when I put it on the ground (gently from the stand) But then times it will run OK and I can fly for 10-12 minutes no problem. Next time I start it, it may do all those bad things. Had 2 or 3 instructors look at it and had no idea other then it was a K&B. Thanks for looking

have you checked all your fuel lines? and checked the low end settings?

I have checked the fuel lines and no I have not checked the low end setting. Are you talking about the low end idle screw?

goirish, I had an older K&B .61 giving me fits once. I would set the needles, it would run fine and then quit a few minutes after taking off. I ended up replacing the engine with a new K&B .61 Twister. I was fooling around with the old engine on the test stand when I found the problem. The o-ring on the low speed needle had aged and shrunk, allowing engine vibration to turn the needle, gradually leaning the mixture. Since the low speed needle effects the mixture well up into the throttle range, and I would always throttle back by half after gaining altitude, this bad o-ring caused me a lot of dead sticks. You might check this by running the engine at different rpm's and watching for the low speed needle turning. Edited to add: You might just try turning the low speed needle with a small screw driver to see how easily it will turn. There should be some resistance.

Those symptoms can point to a lot of things.

Lots of times, when problems come and go, the carb has crud in it. I think K&B carbs have a space inside them where trash or gunk can get trapped. Find someone with K&B experience if other things don't work and see if he'll open it up for you.

Older engines that were run on 100% castor for the oil content would varnish up inside. After a season or two, they'd start to act up like yours. The de-varnishing routine was well known to guys who flew a lot. You'd basically strip it down and remove the varnish. We didn't know about the crockpot back then, and that just might work for a varnished engine. It'd be a heck of a lot easier.

The K&B's came with a variety of carbs. Does yours have a K&B carb or a Perry carb? If you can't even set it on the ground the idle mixture must be wrong.

runs great on the stand. but then I flew it earlier for about 10-12 minutes no problem. Can't understand why it gets so hot. Using 15% non-synthetic. If I adjust the idle screw do I do that at an idle or what is the procedure?

Sorry Bruce. But I believe it is a K&B carb.

pinch off the fuel line to the carb, if it dies right now your too lean..if it runs for awhile then your too rich....if after a few seconds it speeds up and starts to die, or dies you're ok..rightie tightie leans it leftie loosey richens it.
also check your muffler to make sure you dont have something causing excessive back pressure on the engine..if for instance the wrong size exhaust deflector or the wrong muffler. perhaps try taking out the baffle

If nothing else works, that is a symptom of varnishing. Actually, it's a symptom of varnishing no matter what works or doesn't.

And when it gets hot enough the varnish starts to break down and it increases the internal resistances and the engine stops. When it's completely cool, it's pretty much out of the way and the engine runs ok for awhile.

I removed the baffle and it appears to run better. Also put a new plug in. Guess We will have to wait until to tomorrow when I take it to the field. If it some varnish that has built up, how is the best way to remove it? By the way--you guys--you, bruce, ken and minnflyer are really a great help. Wish I had your knowledge.

Which baffle? Inside the muffler? Or do you have one of the REALLY old ones with an exhaust port baffle? Not sure any of the .61's had exhaust port baffles but I had a couple of .40's with them.

Yes inside the muffler--it had a power box muffler. It really does seems to run quicker. We'll see at the field.

Power box muffler? squarish with "p box" on the side? If so thats a muffler for a OS AX series engine. that's why its hot too much pressure

That is what it is. I have removed the baffle. Do you think that will help. Guess I don't have the K&B muffler anymore.

http://www.mecoa.com/kb/61/61-parts.htm
If you wish to get the correct muffler or any other parts. These engines are still in production. Carbs may have changed from what you have. I believe they presently offer a remote needle.

goirish,

Does it have a fuel pump at the rear? if yes, that engine gave me the same problem, it would run fine for 10 to 12 minutes after that, a dead stick, this engine made me crash my 60 size easy sport[:@] now I have nothing to fly[&o].

Mody