Engine Vibration

by patrick hintz in General Tech Discussion 10 years ago

Hello Everyone, I have a 912 100 hp in a kitfox series 6. My instructor was giving me a pre check ride and we were doing a power off stall when we noticed the engine shaking at 3000 ish RPM. We headed back to the airport and landed alittle fast! Upon getting it back to the hanger we noticed the throttle cable point of attachment ( the 2 nuts back to back) the inside came loose and was not allowing the right carb to idle down. I fixed the loose nuts, I also changed spark plugs since I figured I fouled them. I did a test flight and noticed a vibration again around 3300 rpm. I manually synced the carb and lubricated the throttle carb per Rotax Leaf, but vibration is still there on ground run up! anything over that in RPM is smooth. This is a new engine with 85 hrs on it. Any suggestions??? Any help would be greatly appreciated!

Thanks Patrick!

Re: Engine Vibration

by MARK JACKSON » 10 years ago

MARK JACKSON

12 332 11

Hi Patrick

As it is a new engine and it is happening part throttle I would guess it is your floats.

Have you checked them carefully? Have you replaced them with the new type?

This is the first thing I would check as it has happened to us.

Cheers Mark

Thank you said by: patrick hintz

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Re: Engine Vibration

by Roger Lee » 10 years ago

Roger Lee

128 5.28k 4.98k

Hi Patrick,

I agree with Mark. Weigh the floats and make sure each pair is less than 7 grams.
A mechanical sync is just a ballpark starting point. Put a set of gauges on and do a pneumatic sync. New engines can have some cable relaxation or even parts movement within the throttle system and things settle in. Putting the gauges on will also tell you if they are just out of sync or you have a possible obstruction.

Both of these are just part of a diagnoses to make sure you find your problem.

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

Thank you said by: patrick hintz, Ole Jonny Sivertsen

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Engine Vibration

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