912UL Engine vibration on throttle back

by Kevin Stewart in 912 / 914 Technical Questions 12 years ago

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Re: 912UL Engine vibration on throttle back

by Roger Lee » 9 years ago

Roger Lee

127 5.22k 4.84k

Hi Andy,

What Rob said. :)

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

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Re: 912UL Engine vibration on throttle back

by itemprop='name' » 9 years ago

0 0 0

Had a similar problem with our 912ULS2. Turned out to be a worn dog gear in the gearbox. It was replaced and the issue was instantly fixed.

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Re: 912UL Engine vibration on throttle back

by Kevin Stewart » 9 years ago

Kevin Stewart

5 184 0

I too have had this problem and had to have the propshaft and dog gear replaced. Unfortunately the 912 doesn't seem to have automotive levels of reliability. I have had a string of expensive faults to repair in the last few years despite maintaining and running the engine correctly. That said I am not sure that there is a better alternative. Speaking to a Cub owner last night he has had some big bills on his engine too :-(

Kevin

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Re: 912UL Engine vibration on throttle back

by Roger Lee » 9 years ago

Roger Lee

127 5.22k 4.84k

This isn't aimed at anyone in particular so please take no offence. Improper maint and or procedures seem to apply to too many around the world. The Rotax service and repair centers see and hear about these things almost daily. Everyone has been working over the last number of years trying to get good information out there and trying to hold lots of classes to help as many owners as possible. It is worth every owner's time and of course money to take a Rotax class or even two.

Usually the gears in the gearbox are good well through TBO. Most times it is what owners do over long periods that cause issues. Sometimes this is from doing things that they know isn't within the Rotax specs and maint. program or just from lack of knowledge of what the right procedures are.
There are times when parts can fail just because man made them. This is part of all our lives in every product produced in our daily lives.

A few items that can cause down the road issues:
Not ever getting a dynamic prop balance, poor starting and shutdown procedures, weak batteries and hard starts, too many cold hard starts without a properly pre-warmed engine, failing to keep up on carb syncs, no performing gearbox inspections, wrong oils, ect.... will cause issue over the long haul.
The other thing is way too many think they know more than Rotax with millions of run hours and millions of dollars spent and will do things not in keeping with Rotax suggestions.

There is nothing major here that would cause an immediate issue, but will take their toll over time.

I have always advised every Rotax engine owner to download all the manuals for their engine and read them. Know what is in each and where to find information. There are 5 manuals for the 912 and each owner should have them and have read through them. This gets rid of doing things wrong when Joe next door or an A&P with no Rotax experience says to do something against Rotax best practice procedures.

Before I went to my first Rotax class I downloaded all the manuals and read through them cover to cover. Then after class and I was home I read them again and then I actually understood them and it helped implant a better understanding from the beginning and establish a good mental attitude toward maint and the proper and best maint. practices because like everyone else I was new and just starting.

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

Thank you said by: RotaxOwner Admin, Guilherme Tomazini

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Re: 912UL Engine vibration on throttle back

by Greggory Brooks » 6 years ago

Greggory Brooks

0 1 0

Hi Gents,

I realise that this is an old thread but thought I'll just throw in my two cents worth since this thread helped resolve our issue on a Savannah VG with a 912Uls 2007 with a slipper clutch - and a nasty little vibration when throttling back from cruise, all the way from 5100rpm down to 3000rpm.. Even during cruise your hand would go numb from the vibration - really weird (and probably dangerous) landing with a hand you cannot feel.

Any case, we recently bought this Savannah at 1127 hours and from the start we had a vibration which was becoming worse over time. We flew approximately 90 hours in 6 months and had to replace broken clamps and oil cooler that seem to have broken due to vibration. The previous owners (x2) are at the same airfield and had no problems according to them. The plane had however had a prop-strike +/- 200 hours ago in 2014. Prop had been replaced and engine and gearbox checked. We balanced prop and reset the pitch multiple times. Carbs were balanced and flanges and engine mounts checked. When reading this thread things started making sense. We stripped the gearbox and found a worn dog hub and main gear. The Bellville washers were also very worn. Put it back together 3 days back and behold... no more vibration. We are currently putting a few hours on it in the circuit as the gearbox stripdown has been a new experience for us and we are still nervous about it....

Overall this is the best the aircraft has flown since we have had it.
We have checked the service manuals and all service bulletins were adhered to and maintenance done as far as we can see. So the aircraft made it to 1100 odd hours before any issues arose and we strongly suspect the reason to be the prop-strike.

Thank you very much for an awesome site and to all the contributors who through knowledge and experience helped solve this issue.

Gregg

Thank you said by: RotaxOwner Admin, Guilherme Tomazini, Glenn Martin

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912UL Engine vibration on throttle back

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