at which rpm needle jet begin to raise? what are signs of clogged bypass holes?

by nicola di biase in 912 / 914 Technical Questions 5 weeks ago

I read a lot of informations on how the bing 64 works in general terms and details.

But i have never understood whether from idle to 3000 rpm (where there are always more or less marked roughnesses in rotax 912 engines) only the idle jet and the bypass holes are involved or if at these rpm the needle jet has already started to lift.

Many 912's are rought from 2000 to 3000. I suspect that in addtion of dirty idle jets, clogged bypass holes are the cause and a lot of people do not even know their existence!

In your experience what are the signs of clogged bypass holes?

thanks

Re: at which rpm needle jet begin to raise? what are signs of clogged bypass holes?

by Roger Lee » 5 weeks ago

Roger Lee

131 5.38k 5.44k

At every annual I weigh the floats and clean the idle jets. I have found 75 of the idle jets partially clogged or fully clogged. So no I just do it for my customers no matter what aircraft they fly. I'm teaching a Rotax class this weekend and these are two things I teach them. Since we use a real aircraft (a FD CTSW this time) they get to learn the easy way to pop the carbs out and then they all get to see how to weigh floats, look for clogged idle jets and how to clean an idle jet without damaging it. It's actually very easy and quick.

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

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Re: at which rpm needle jet begin to raise? what are signs of clogged bypass holes?

by Jeff B » 5 weeks ago

Jeff B

14 683 2.46k

Nicola,

Here is a great article by Brian Carpenter explaining the idle circuit and when the each fuel delivery route is in play. There are two more related articles (parts 1 & 2) which you can find with a search. I don’t impress easily, but I find most everything Brian publishes impressive.

https://electricmotorglider.com/wp-content/uploads/2017/04/CV-Carb-Part-3-web-1.pdf

Thank you said by: Sean Griffin

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at which rpm needle jet begin to raise? what are signs of clogged bypass holes?

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