Engine Roughness

by Don Hudgeon in 912 / 914 Technical Questions 14 years ago

In the past week I have noticed engine roughness ONLY at 2500 to 3200 RPM. The idle down to 1400 is smooth. This is a 912UL with 230 hrs total time. Last winter I raised the needle valves. It is now 15 to 20C most days. Should I be lowering them again? Carbs are synced and plugs are new. Any suggestions

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Re: Engine Roughness

by RotaxOwner Admin » 14 years ago

RotaxOwner Admin

59 1.6k 16.6k

The RPM range of 2500 - 4000 is the range that is most affected by the needle positions.
It is a good possibility that for your configuration, and the change to warmer conditions, moving the needles back down to their previous positions (likely the second notch from the top) will result in smoother operation in that RPM range.

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Re: Engine Roughness

by Don Hudgeon » 14 years ago

Don Hudgeon

6 33 0

I changed the needle positions back to summer mode(second notch from the top) and it smoothed out a lot. Also ordered a Carbmate and will recheck the sync when it arrives.
Thanks for the help.
Don

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Re: Engine Roughness

by Ahmed Sumaan Rafeeq » 2 years ago

Ahmed Sumaan Rafeeq

2 1 3

operate the mixture at engine rough running and let me know 25000-3200rpm observations.

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Re: Engine Roughness

by Charles Churchman » 2 years ago

Charles Churchman

0 5 6

We noticed roughness around 3000 rpm in our 912, with 300 hours on it. One bottom plug turned out to be oil fouled, causing the problem. The plugs had 50 hours on them, using 100 LL and TCP added regularly. Once cleaned, the roughness went away.

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Re: Engine Roughness

by Sean Griffin » 2 years ago

Sean Griffin

51 1.23k 5.37k

" The idle down to 1400 is smooth".

Idle rpm is far too low. Idle, for engine stop, need not be any lower than 1600-1800 rpm. Idle for ground operations, minimum 2000 better above 2200 rpm.

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