Help!!! I have an older model OS MAX 40 FP engine that has started to overheat. The engine has spent a number of years (multiple, but that is another story) in a box waiting for the completion of the trainer (Kadet Mk 2). The model was recently completed and the plane flew fine for approx. 10 times.

During the last 2 flight the engine ran fine (approx. 50% throttle) for 10 minutes and then started to miss as if it was running out of fuel. Upon landing I noticed that the engine was rather hot (fuel tank was approx. 50% full). Needle valve settings had not been changed.

Any suggestions on what may have changed that would make the motor overheat???

The engine may be running too lean. Open the needles 1/4 turn or gun the engine on the ground and using a tach, decrease the rpm by 300 kliks by richening the high speed needle.
Full throttle...hold the nose up 45 degs and if the rpm decreases...it's still too lean, richen the high speed needle.
IF that does not help.....put the engine back in the box where it belongs [8D]
A student at our club recently bought one new, same problem after two months. In the beginning though....the carb was leaking..so check that seal. It is baffling why that engine gets over heated.

As compared to......... It may not be overheating just because it started to act up, glow engines get quite hot. From your basic description there are too many things to list that might be the cause of it not running properly.

If the temperature has changed significantly since the engien was tuned, then it may very well need re-tuning. Our engines have to be set a little richer as it gets cooler, but unless there's been a 20 degree drop in temps, it's probably something else.

More info would help.
Dennis-

It may be breaking in now and just need retuning. You got some good suggestions on how to set it up. I would retune it and see where it goes. You may also want to take a look at the glow plug. It may have contaminants on it from break in. You may need a new one.

Mark Shuman

Great Advice above!!.. Do as they say.. And retune.. After you
get the engine running peak it out, then back-off(richen it) about
a quarter turn or so.. roughly lower RPM about 3-400 and it
should be OK.. If you have problems.. Check for air leaks..

Thanks for all the info. I did notice fuel leaking at the needle valve connection, it would likely pull in air and potentially make the engine run lean. I changed the fuel line and re tuned the engine, both high and low speed needles. Test ran in the garage and no problems.

The plane flew last night. The engine ran fine for approximately 15 minutes and then stopped. Unfortunately it was due to hard contact with a fence! 4 hours of repairs and I am ready to try again.

I have always said that I would crash sooner or later.

NJJD