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Hot engine cuts at idle

  • Richard Lyon
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1 month 1 week ago #17779 by Richard Lyon
Richard Lyon created the topic: Hot engine cuts at idle
Our Rotax 912ULS has done around 350hrs, regularly serviced, runs on Mogas, and carb balancing completed recently. We have a recent problem with engine cutting at low revs.

Performance on pre-flight check, engine warm, normal: min. idle around 1,600. However, on a recent approach, throttle idle, engine cut. Subsequent test, on the ground, after a flight (so engine hot), had the same result.

Linkage and stops are OK. We’re checking the carb float needles level with fuel, cleaning the jets. We’ll re-check performance with engine warm and hot.

Would appreciate further suggestions for investigation. Engine management system perhaps?
Thanks in advance.

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1 month 1 week ago #17780 by Roger Lee
Roger Lee replied the topic: Hot engine cuts at idle
If you were at idle then you were in the idle circuit in the carb. If the carb sync has been a short time back I would check it again because something may have changed. I would do this first. If you are using gauges for the sync a clogged idle circuit will show up as a high vacuum reading over the unaffected carb. You may also want to pull the idle jet out and take a 16 ga. wire, strip it back about 2"-3" and then pull out 1 strand of the twisted wire and use that 1 strand to rod down through the idle jet. It's a tiny hole. Follow that with some carb cleaner in a spray can and then some high pressure air. Flush some carb cleaner and air through the jet in the carb bowl to.

There is a slight possibility that you have a heavy float and it's flooding out. You'll know this when you pull the bowl and look at the floats and weigh them.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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1 month 1 week ago #17782 by Richard Lyon
Richard Lyon replied the topic: Hot engine cuts at idle
Very many thanks, Roger - we'll action this tomorrow.

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