High RPM Roughness

Re: High RPM Roughness

by JD Wade » 12 years ago

JD Wade

2 6 0

The engine is a 912 ULS with 120 hours. No recent maintenance. I hope to find time this weekend to troubleshoot the problem. I'll start by looking at the plugs, wiring, fuel filter, then carbs. My Rans has a drip bowl under the carbs, so I will need to remove the carbs before I can drop the bowls. Of course I hope to find something simple as the cause! Thanks for everyone's suggestions.

Re: High RPM Roughness

by Roger Lee » 12 years ago

Roger Lee

131 5.38k 5.44k

Many issues are easy, it's just us owners that make them hard to find. ;)

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

Re: High RPM Roughness

by MARK JACKSON » 12 years ago

MARK JACKSON

12 332 11

Hi JD

Do you have a fuel pressure guage fitted and if so was there a drop in pressure. If not have you got the new fuel pump fitted or the
AC pump.

If you have the AC pump fitted it could be that the pump is failing.

Mark

Re: High RPM Roughness

by JD Wade » 12 years ago

JD Wade

2 6 0

I have the new fuel pump. Fuel pressure remained constant, electric fuel pump made no difference.

Re: High RPM Roughness

by JD Wade » 12 years ago

JD Wade

2 6 0

Got to the airplane this afternoon. Plugs all look good to me, no obvious differences in the plugs. Fuel filter is fine. Removed both carbs, there was a small amount of soft sediment adherent to the bowls of both carbs. Several small floating flecks of soft material were in both bowls. One small fleck in one bowl was firmer but I could pulverize it with my finger tips. All jet passages appear to be open. The idle jets have a very small opening, I can barely see light through them. I guess this is normal.

Not sure I have found the problem, altho I guess one of the small flecks could have obstructed the main jet.