My RV12 with the 912ULS will not run smooth at WOT or get T/O power after it's HOT. 

Last flight everything was fine until I left the power up at altitude to see what I could get for RPM in level flight. It started to run rough at 5400 RPM. After returning to the field I as unable to get more than 4400 RPM. The problem is always after the engine is hot.

Don't waste your time with suggestions to trouble shoot only because we've been through everything at least twice. But please, if you have had or know someone who has had the problem of not running at full power after the engine gets HOT, I'd love to hear what fixed it.


  • Re: WOT miss when HOT

    by » one month ago

    The problem has been fixed thanks to Roger Lee. I'm sure a lot of you know Roger or have seen his post on multiple forums. Well, he's come through again.

    After talking for almost an hour on Friday and not coming up with an answer Roger said, "one more thing, check the choke shaft for a punch mark tell me which way it's facing". I did (after I found the small punch mark) and the 2/4 carburetor choke was assembled wrong. Punch mark 180 degrees out. After the 5 min. it took to remove the linkage, turn the shaft and put the linkage back on, I ran the engine and it seemed to be fixed. Saturday I put the cowl back on and went flying. Everything was as it should be. Today I flew again and did everything I could do to make it screw up, including sitting on the ramp for 15 min. after flying, to let everything get hotter. I did another T/O and then a touch and go and then declared the problem fixed.

    There a lot of questions: how long has it been that way? There doesn't appear to be any reason the previous owner would have been into the choke in the 150 hrs. that he had it. Why did it the wait 30+ hrs. that I flew it? How did it run as good as it did? I am not knowing!

    Thanks Roger


    Thank you said by: Roger Lee, RotaxOwner Admin

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