912 ULS 3000 RPM Vibration

Re: 912 ULS 3000 RPM Vibration

by Gary Masters » 12 years ago

Gary Masters

0 1 0

Hi Doug,
Have you tried new Jet needles & needle jets yet? as i have recently experienced a similar problem with an aircraft of similar hours,
replaced the needled & jets - problem gone.
Gary

Re: 912 ULS 3000 RPM Vibration

by Douglas Gunn » 12 years ago

Douglas Gunn

2 16 13

Gary:

I have not done anything with the needle jets or jet needles yet. I am going to try to sync at 3000 rpms as Roger suggested and then will try changing the jets in the carbs. This was one of my original thoughts as I found a lot of varnish when I rebuilt the carbs and probably should have changed them then.

I have had several people with much more experience than me fly the plane recently for their opinion, and all have thought that the problem is very minor (if a problem at all) and is common in this type of engine.

Thanks for the suggestion.

Doug

Re: 912 ULS 3000 RPM Vibration

by Roger Lee » 12 years ago

Roger Lee

131 5.38k 5.44k

Hi Doug,

Use at least 3500 rpm for your upper rpm sync. My bet is since you synced them at 2500 you will find them off at 3500. Any varnish found during a carb inspection or rebuild showed entail a good deep clean because it can hide in the smaller passages, but try the sync first since it's the easiest thing to do.

---

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

Re: 912 ULS 3000 RPM Vibration

by Tony Garrett » 12 years ago

Tony Garrett

20 37 11

Good morning Douglas
I have a very similar vibration problem. I have a Savannah (Zenith 750) with a 100 hp ULS and ~500 hours in about 3 years. I have significant vibration between 2800 and 3200 RPM. I have tried everything mentioned above and more. Nothing seemed to help. I am convinced it is a design feature for the ULS. I did flatten (reduce) the prop pitch slightly. This unloads the engine a little. Seems to have helped the vibration some. Telling the passenger it is caused by the special race cam you installed makes them happy.

Tony

Re: 912 ULS 3000 RPM Vibration

by Tony Garrett » 12 years ago

Tony Garrett

20 37 11

Sometimes the problem/solution is too simple to recognize. I had the same ~3000 RPM vibration problem with my ULS 100 engine (new in 2010). I tried many fixes. None worked. Recently I noticed cracks in one end of the vent tube connecting the right carb to the airbox. See the attached pictures. The tube was only about two years old. I replaced the tube and the vibration disappeared plus now I get an extra 100 RPM during climb. Strangely the left carb vent tube still looks new.

P1020104e.jpg (You do not have access to download this file.)

P1020123e.jpg (You do not have access to download this file.)