That is very true, but before assuming that the glow plug itself is bad, it is a good idea to try and see if you can get the engine NOT to change RPM's when the glow plug is removed, by leaning the low end even more.

Also poor fuel flow or lack of muffler pressure can cause the same sympton.

Going the other way, the Evolutions are famous for their "grey goo", that consists of metalic particles which wear off of new engines.

This can foul the plug and can be the cause of the need to change it on a newer engines.

Usually the "Grey Goo" condition disappears after a few gallons are run through the engine.

The goo can also clog the muffler pressure nipple, so clean it frequently with a small hex key, particularly when the engine is relatively new.



One note:

The Evolution engines come with "long" glow plugs.... that are very similiar in length to four stroke plugs.

This is what the manufacturer uses.

O.S. A3 plugs will work but they have a shorter length.
This can affect inverted mount engines, particularly during startup attempts.

Just installed a several year old Evo 46 in my SSE and test ran today. Problem was not that it would not run, but that it would not shut down even with the throttle completely closed. Obviously I have an air leak and it probably is in the fuel tank or lines but during inspection, i found a puddle of after run oil on the table just below the front of the engine, apparently coming from the front bearing. Does this bearing/seal commonly go bad and would it suck enough air to keep engine running with completely closed throttle? i have just rebuilt the plane and thought I had replaced all the fuel lines, etc. Will pull tank and retest all connections.

Got lucky, found that the carb was not seated properly, loosened the binding clamp and compressed the carb into the engine and tightened, also sealed the back plate but it showed no signs of leaking. The carb is supposed to have two o-ring/ gaskets under carb, mine has only one, will order correct set. Changed from an OS A3 to a Mc Coy MC-59 [long threads] and she purrs like a kitten until you open it up and the she roars.

Gary