Hi all, I was looking for some information or someone to help with a problem I am having with my new Enya 120 4c engine. The problem seems to be with power !! I have a very realiable idle (1950 rpm's) great transition and no sputtering on low end. The prop I started out with was a 14x6 MA and have progressed all the way up to a 15X8 MA. The engine runs normal temperature at full throttle but misses and bangs (almost like a backfire or pre-detonation) at full throttle. With the 14X6 prop I was turning 10,000 rpm's on the ground and with the 15x8 I was turning 9400rpms. I run Byron 15% and the engine is on a Great Planes spacewalker (weight is 10lbs 4oz). It seems to have very little vertical and can not hold any knife edge at all. All parts are seated and sealed (including carb) and valves are adjusted to .05 as per manufacturer specs. This engine was new in box and has had 3/4 gallon of fuel ran through it. Someone suggested dropping to a lower % nitro since it has no head shim for the higher nitro. The plug I run in it is the stock one that came in the box. Will a Enya #3 plug work better? Also there seems to be very little adjustment on the high speed needle as more than 2-3 clicks either way seems too rich or too lean shutting off down the engine.Thanks and any help woudl be appreciated.

Backfireing is or missing is an almost sure sign of being too lean with 4-strokes. If that happens at all, you are too lean, regardless of what else you think might be going on. Richen it up and see if that helps.

To get better pull, go to a larger diameter, lower pitch prop.

What prop range does the manual suggest? I think some of the props you listed are too small for that engine, but since I haven't run one of those myself, I'm not sure.

Also, MA props in that size aren't as efficient as some other brands, so you might try another prop.

I might try an APC 15x6 or 16x6 and see what happens. I'm running a 13x6 on an OS .61FS right now, which worked out to be the best prop I tried.

Also, I'm not sure what engine range is recommended for your plane, but at 10lbs, you may not get much vertical. And the Spacewalker isn't exactly designed for knife edge flight or verticals anyway. (not that it's not possible, but it's not designed for it. The Spacewalker is closer to a cub than to an Extra).

Thanks Montague , the great planes spacewalker calls for a 90 size 4stroke and I figured the Enya would be plenty powerfull. I will use a larger prop and richen it up a little to see if that helps. Thanks any other advice is welcome.

Check where the intake manifold bolts on to the head. I have seen many of the Enya's leak in that area. Cut a slightly thicker gasket and seal with a gasket sealer. The tank position is also critical with these engines.

Cheers,