kpin
Well-Known Member
- Joined
- Jul 27, 2009
- Messages
- 155
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Any thoughts? Last week while giving a short acro ride I noticed a slight loss in available power as well as a developing roughness and missfireing. I nursed the aircraft back to the airport and landed uneventfully. When I pulled the power back to 1500 RPM on landing the roughness and missfireing went away. On inspection I found the missfireing occures on both mags and at an RPM above 2000. I checked compression, all cyklinders in the mid 70's. Inspection the plugs I found the bottom plugs on the left quite wet and the top plugs dry but still on the rich side. My first thought while in the air was a stuck valve but this situation occures onlu at high RPM and when the engine is both cold or hot. This is not typical of a stuck valve. I then removed the lower half of the cowling and again did a run up. To my surprise all seemed well, roughness gone. I found that the crossover exhaust system had burnt a hole through the scat hose connecting the airfilter to the injector system. Could the hot air from the exaust pipe created an over rich conditon and power loss? Could the poping be unburnt gasses due to the poor combustion be refireing in the hot exhaust pipe causing the missfireing sound? I reassembles with new scat anddid another run up and again ran well. Lycoming says yes it is possible that was my problem. IA say possiblebut unlikely. I am goin to do some more extensive ground testing and the fly. What do you think?
