Rotax 503 60 sec Idle

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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Tango Bravo 1
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Joined: Fri Dec 13, 2019 1:20 pm

Rotax 503 60 sec Idle

Post by Tango Bravo 1 »

My 503 in a T-bird 1 starts on choke runs until it loads up, re-start choke off, it runs about 60 seconds then just runs out of gas (apparently) then dies. When I check the fuel bowls they are more than half full. I have checked the carbs 3 or 4 times they look like new. This motor has about 3 hours on it. It is 20 years old though. I've tried to pump the squeeze bulb doesn't help. Really frustrating.
Tango Bravo 1
Posts: 4
Joined: Fri Dec 13, 2019 1:20 pm

Re: Rotax 503 60 sec Idle

Post by Tango Bravo 1 »

What! No help? Surely I am not the only one to have this problem.
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drseti
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Re: Rotax 503 60 sec Idle

Post by drseti »

Have you weighed the floats in your carb float bowl lately? They are a known Rotax problem area. Not sure what the floats should weigh for a 501 - in a 912, they should be 3.5 grams max per float (7 g per pair), with typical running 2.8 g ea.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Tango Bravo 1
Posts: 4
Joined: Fri Dec 13, 2019 1:20 pm

Re: Rotax 503 60 sec Idle

Post by Tango Bravo 1 »

I have not weighed them but they float high in the gas, and the bowl has fuel in it almost full when I take them off. Thanks for your response. I am trying everything I can.
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drseti
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Re: Rotax 503 60 sec Idle

Post by drseti »

When you remove the float bowls, the horizontal pin on the floats should be even with the surface of the fuel. If that's what you're seeing, then you can rule out the floats (and it's back to the drawing board).

The nearest Rotax 2-stroke experts to me are Bob and Lori Keech at Cloud 9 Aerosport, St Mary's PA. You might look them up and give them a call.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
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