912 knocking with cold weather

by Patrick COSNARD in 912 / 914 Technical Questions 6 years ago

Bonjour,

My 912 knocks when cold, only with cold weather below 3.500 rpm. Changing slightly RPM remove knocking for a time. When hot, everything is OK......

Thank you for your help

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Re: 912 knocking with cold weather

by Bill Hertzel » 6 years ago

Bill Hertzel

13 1.95k 7.98k

I don't think that what you may be hearing is Knocking.
Knocking is encouraged with Higher RPMs, Higher Temperatures and Higher Compression.

If it disappears by increasing the throttle, it is something other than Knocking.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: 912 knocking with cold weather

by Roger Lee » 6 years ago

Roger Lee

128 5.28k 4.98k

When you start and warm up you should be at least 2000 rpm, but not over 2500 rpm.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: 912 knocking with cold weather

by Patrick COSNARD » 6 years ago

Patrick COSNARD

3 7 1

Bonjour,

Thank you for your answer. Knocking is probably not the right word, but sorry, i'm French :-)
Perhaps it woulb be better the engine works roughly. The only way to stop it is to increase RPM. On starting, the engine works well 1 minute and then begin to turn roughly.
Bon week-end

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Re: 912 knocking with cold weather

by Roger Lee » 6 years ago

Roger Lee

128 5.28k 4.98k

The roughness can still come from idling too low, but it could easily come from out of sync carbs or a clogged idle circuit. You need to check the sync on the carbs.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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Re: 912 knocking with cold weather

by Patrick COSNARD » 6 years ago

Patrick COSNARD

3 7 1

Sync is OK. Problem is only when engine is cold, so clogged idle circuit should create same problem with an hot engine.

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912 knocking with cold weather

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