Rotax 912 ULS severe vibration at engine startup

by Robert Mikkins in 912 / 914 Technical Questions 13 years ago

hi to all, i am having severe vibrations with my 912 ULS at startup (just 50 hours used) which sometimes continue to 7 to 8 seconds and then becomes smooth again. during this rough startup, engine speed is about 1000 rpm and when it becomes smooth, it goes back to idle speed that i've set.i have sync'ed it with carb mate. so no synchronization issues after startup. checked spark plugs, carburetors and ignition unit, everything is clear. any advice please??

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Re: Rotax 912 ULS severe vibration at engine startup

by Alan Arnold » 13 years ago

Alan Arnold

20 188 145

Robert,

I had this problem several years ago with a 582. It turned out one of my carbs was flooding during start and wouldn't clear the excess fuel for several seconds. It seemed like the engine was going to shake itself off the mounts until it suddenly cleared and ran smooth. This would only occur during a cold start when the chock/enrichment circuit was engaged.

Hope this helps.

Alan

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Re: Rotax 912 ULS severe vibration at engine startup

by bill martin » 13 years ago

bill martin

10 757 0

Robert,

You might check the fuel enricheners. Sometimes they stick and don't always return all the way to the off position when you release them but engine vibration usually closes them pretty quickly. Don't know if the soft start module could cause the vibration but they are energized for about the same amount of time you mention. What is your normal idle speed?

Bill.

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Re: Rotax 912 ULS severe vibration at engine startup

by Robert Mikkins » 13 years ago

Robert Mikkins

1 2 0

i have checked the carburetors and they are working fine.
also fuel enrichener is woking fine without effects of vibration.
idle speed is set to 1800 rpm.

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Re: Rotax 912 ULS severe vibration at engine startup

by Robert Mikkins » 13 years ago

Robert Mikkins

1 2 0

rotax experts.......... any sujjestions please??

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Re: Rotax 912 ULS severe vibration at engine startup

by Mike Goodrich » 13 years ago

Mike Goodrich

8 123 0

Robert
I had problems with my 914 and checked everything like you did. The problem was I missed some debris in the slow running jet. I'm not saying this is your problem, just that you probably missed something first time around.
Mike G

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Rotax 912 ULS severe vibration at engine startup

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