Carburators are loose

[Wheels]

My 10 hour old 912UL is running smoothly, or it was. I noticed a little roughness a few days ago an inspected to see if anything had slipped in the linkage department.
The number 1 carb had clocked about 2 degrees. that would upset the float condition so I grabbed it by hand and easily turned it back to vertical. I checked the screw on the clamp, I loosened it completely and made certain the carburetor was seated completely in the boot. I tightened it back down and flew an hour to see how things faired. It didn't stay at the 1200 position, in fact I notice both are slightly off. I video taped the engine at idle and at 4000 RPM to see if I could determine a heavy vibration and I don't think its there. I may have to change the shutter speed on the camera to make sure there isn't a lag in the video but honestly, the naked eye shows nothing abnormal either. anyone else seen this behavior before. I"m convinced the torques are good on the rubber mounts and such. I don't want to damage the boot, but they aren't holding up.

[avidflyer]

I think on the 582 carbs, they were supposed to be tightened till there was a certain distance left on the clamp. 8 MM if I remember right. Is there such a thing for the 912? JImChuk

[Av8r3400]

The new engines actually have a spacer in the clamp to prevent over tightening. I'm not a fan of that design.

[Wheels]

I shaved 1 mm off the spacer and reinstalled it. I flew for two hours and did multiple touch and goes and other fun things to wring out the engine at all RPMs. the carbs stayed put.

That spacer was 8 millimeter and I only had trouble with the left one. I didn't touch the right side. (no.2 aft looking forward.) I put on the nose cone tonight, I"m almost satisfied.

[cap01]

thanks for the tip. i only have the issue on the right side.

[Wheels]

I may be wrong but I think the carb was probably turning during start up when the choke cable was being pulled. It would certainly pull in the direction of rotation and the vibration at start up is often quite exciting for the little fella.

[Dorsal]

But the choke cable jacket is referenced to the carb so it would only be pulling against itself?

[Wheels]

Hey! your spot on! thanks. Um can I retract my last post before anyone else sees it?

[Slyfox]

Jay, after I bought my 912uls I got some carb sockets that where made so they wouldn't split. I never had trouble with loose carbs. but than again being the rebel I am, I might of removed the spacers to make sure the carbs stay put. I'll have to look.
Another thing I do, quit different, is I put my idle way down to almost nothing, if I actually pulled back all the way on my throttle I can stop the motor. I never go that low, just for shut off and startup. My engine is real bad for kick back, so I keep the mags off and pull the choke and crank the engine to a count of 6 or 6 seconds. than I turn the mags on and pull the throttle all the way back and when I know it's wanting to start, slowly increase the idle to 2000. been doing this for ever. a very nice smooth start up. On shut down I pull the throttle back all the way and turn off the mags at the same time, again a nice smooth shut off.
Now if you don't fly very much or let it sit for like a week, sometimes it still won't start, I just turn off the mags and pull the choke and give it a few more seconds of crank. than try again.
hope this helps. another advantage to having the idle go way back is final to landing, I can pull it way back and get some good engine braking. that with a nice slip and adjustable prop that's flattened for landing will give me a real nice short landing. Gawd these planes are fun. :D

steve

[cap01]

i know my engine was bouncing around a bit, most on roll out due to a sub idle. even would get a gas smell and almost quit running. also wouldn't run smoother after first start up until full warm. this is on a new factory engine. found the carb needles were in the incorrect position from the factory. maint manual states they are supposed to be in the second position from the top from rotax, mine were in the third. runs like a different engine after i corrected the position.