912UL Running Rough

Re: 912UL Running Rough

by Av8r3400 . » 11 years ago

Av8r3400 .

2 23 0

Well-- I took apart the carbs again today for the 436th time. Nothing to tell. The slides are/were just fine. There is no galling or spalling between the pistons and bores. The needles are fine, the baffles are new. The sync is near perfect. Checked with electronic and analog gages.

Also eliminated the ACS switch for toggles and replaced the new spark plugs with new-new spark plugs.

I am totally at my wits end, here. Completely pissed. I'm completely sick of just blindly throwing money at this motor hoping to fix the issue.

Re: 912UL Running Rough

by Rob Seaton » 11 years ago

Rob Seaton

3 1.32k 251

I had a look through your posts and did not see any mention of the carb sockets, have you replaced them?

Re: 912UL Running Rough

by Rob Seaton » 11 years ago

Rob Seaton

3 1.32k 251

they would be 20+ years old and a IV is very hard on the sockets. also look for signs of over-torque of the socket clamp and the mounting bolts; both will damage the sockets and cause an induction leak.

Re: 912UL Running Rough

by Av8r3400 . » 11 years ago

Av8r3400 .

2 23 0

Yes that is a very good idea. I was just talking about them this evening with some friends at an EAA chapter event.

Sorry, Rotax, but my replacements will come from elsewhere. http://jbmindustries.com/. Ordering them tonight.

Re: 912UL Running Rough

by Av8r3400 . » 11 years ago

Av8r3400 .

2 23 0

After going though the carbs again, installing the new boots and switching the carbs side to side ( with all the a associated re plumbing and cable rerouting ) the problem is fixed.

In the end I'm really not sure what I fixed, but the 2000-3000 roughness is mostly (95%) gone.