• Re: Tip of the day-The idle Jet

    by » 4 months ago

    Roger, great tip. I recently overhauled both carbs and during carb sync, I had one carb that idled too high (2150 RPM). I was unable to get it down to the 1800 rpm that I would like. What about that idle jet screw that should be bottomed out and backed off one and one-half turns. The one that "rarely needs adjusting". Could that cause this idle problem?


  • Re: Tip of the day-The idle Jet

    by » 4 months ago

    I'm going to guess that the butterfly valve isn't quite in the correct position. When I overhaul carbs and install the butterfly shaft and then put the butterfly in place and put the two screws in I do not tighten them at this point. I put the retaining bracket in place on the outside and move around the butterfly so I know it is absolutely sealed and in correct position in the throat of the carb. Then I tighten and peen the two screws. If you don't put the bracket in place which helps position the shaft and butterfly before you tighten those two small screws your butterfly valve can be a tad out of place. That bracket on the outside and around the shaft help position it. If it isn't set right and has any gap around the edges and can't really shut down the fuel and air flow then that might cause the carb to have a higher idle than wanted. 

    I'm leaning on this since you said you just overhauled the carbs.


    Do make sure the idle mixture screw on the bottom of the carb is 1.5 turns out from the fully screwed in.


    I overhaul a lot of carbs so if you need help let me know.

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

    Thank you said by: RotaxOwner Admin

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