912 ULS rough running at 2350 to 2450 rpm

Hi Gudmundur,

That's interesting, did you have an wear on the splines of the propshaft? That's what I had that gave rise to roughness at different RPM.

Alan's gearbox may have dog clutch wear, like Gudmunder however I suggest exploring the least costly/easier options before going down this track😈

Hi

No there was no wear in the spline.  I never found any debrief on the magnet. 

People could hear the clanking sound from the plane when landing, I did not hear anything sitting in the plane but engine did shake a lot að the low rpm. 

Earlier I had zinced the carb, put on carbs from other engine, balanced the prop with no result,

I have propeller from Kiev Propeller it's a heavy one. 

It's possible to test with lighter prop, then you maybe don't get the "resonance" prop/gear, easy way if shaking stop it possible the gear. 

I tried eProp, then this shake stopped but of course i fixed the gear.   

Best Reg
GA.

Hi.

Sean, yes my idea was to try everything else first. $$  So i lend 2 carbs from a friend and put them on yesterday, syncronised them, and the roughnes stopped :-)  So now i will take 1 of mine and put on and see what happenes. If it still is good i will take the other one and see.

This way i can perhaps narrow the problemt down to one specific carb. ( or both ).

i will have to take them apart again and see if i can find the problem 

Gudmundur i am pleased you fixed the problem. I saw some youtube of mecanics telling of the problem with wear in the gearbox when operating it with low rpm.  When i bought my plane it had 80 hours and ran with 4700 rpm in cruise. After a year i piched the prop to 4900 rpm. in cruise. 6 months ago i piched it to 5100 rpm. in cruise. In takeoff roll i can get 5200 rpm. now instead of 5000 rpm.  

I will keep you posted ....

Best regards Allan

Hi Allen,

Why not have an "experienced" carb overhaul person just do an overhaul?

There's a good chance just pulling them apart that you won't see anything. Overhauling a lot of carbs teaches you certain things to look for.