One possible problem is Engine break in
It seems you are talking about the Enya 45 6001 with plain bearing that has an iron piston. Enya Iron piston engines needs special break in. The iron piston will grow more then the sleeve when it gets hotter and when the engine is not fully broken in it will sag when going up as the temperature rise and the piston expand causing to much friction.
Some people say it will take a long long time to break in an Enya Iron engine and that is true if you do not use the proper technique. Enya Iron engines takes no less then 40 min of bench running and it should not take longer then 1:30H for the tightest engine. The time will depend how tight the P/L fit.
I know of people that ran an Enya Iron Engine for 5hours on the bench and the engine still sag when going up. The mistake was running the engine constant rpm and a bit rich. This way it will never break in.
This is how I break in my Enya Iron Engines:
Fuel 0% Nitro 20% castor oil only
10 runs of 1 min. needle so the engine is burbling between 4 and 2. Let the engine fully cool before starting again
8 runs of 2min. with the same setting
4 runs of 3 min. same setting.
5 runs of 6 min. with the needle in the same setting but this time pinch the fuel line to sustain peak rpm for 10s, then wait 20s and repeat pinching process til the end of the run. Start pinching the fuel line slowly and watch the rpm to increase slowly, if engine start to lower rpm you went to far, back up a bit. The idea here is to make the engine run as hard as it can for 10s. If you can, measure the maximum sustain RPM. You should notice that this number will improve. If after the 5 runs you still notice that the top rpm is still improving do a few more runs like this.
You should avoid running the engine deep 4 stroking during break in or when new, it will put a lot of stress on the conrod/crank pin and that *can* cause premature wear of the conrod brass bushing.
For the Enya 45 Iron I suggest using a 10x5 prop for break in on the bench.
If the engine is four stroking in level going this fast, it does not sound the problem is the chip muffler.
Martin
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