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Hot engine cuts at idle

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7 months 6 days ago #17779 by 2greens1red
Hot engine cuts at idle was created by 2greens1red
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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7 months 5 days ago #17780 by Roger Lee
Replied by Roger Lee on 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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7 months 5 days ago #17782 by 2greens1red
Replied by 2greens1red on topic Hot engine cuts at idle
Very many thanks, Roger - we'll action this tomorrow.

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