Won't run off choke

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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Won't run off choke

Postby Tango Bravo 1 » Mon Jan 13, 2020 5:50 pm

Can someone please tell me why this 503 will not run off choke??? Surely I'm not the only one that has had this problem.

3Dreaming
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Re: Won't run off choke

Postby 3Dreaming » Mon Jan 13, 2020 7:06 pm

Tango Bravo 1 wrote:Can someone please tell me why this 503 will not run off choke??? Surely I'm not the only one that has had this problem.


Not many here with 503 experience.

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drseti
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Re: Won't run off choke

Postby drseti » Mon Jan 13, 2020 10:19 pm

If your 503 has a Bing carb, it really doesn't have a choke, in the conventional sense. It has an enriching starting carburetor, which only works if the throttle is fully closed. If you're running throttle up with choke on, the engine will stumble. Use the choke only for starting, keep the throttle against the idle stop until the engine warms up, and then close the choke before you open the throttle, and your engine should purr.
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
fly@AvSport.org
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US

chicagorandy
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Re: Won't run off choke

Postby chicagorandy » Mon Jan 13, 2020 10:29 pm

And if it doesn't do as Paul advises? It is often an issue with the tiny jets within the carb being clogged or constricted by even tinier debris.
"Don't believe everything you read on the internet" - Abraham Lincoln

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drseti
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Re: Won't run off choke

Postby drseti » Mon Jan 13, 2020 11:28 pm

chicagorandy wrote:And if it doesn't do as Paul advises? It is often an issue with the tiny jets within the carb being clogged or constricted by even tinier debris.


True, but I always try the simplest fixes first!
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
fly@AvSport.org
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US

HAPPYDAN
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Re: Won't run off choke

Postby HAPPYDAN » Tue Jan 14, 2020 11:59 am

When our older dirt bikes (carbs) did that, we always checked for air leaks between the carb/manifold/cylinder/head gasket first. Not knowing what a 503 is, if it's a 2 stroker, check the head gasket carefully. They have a tendency to burn out on 2 strokes, but are dead simple to replace. Oftentimes, it was just a loose bolt (bad vibrations) somewhere in the connection.

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drseti
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Re: Won't run off choke

Postby drseti » Tue Jan 14, 2020 12:15 pm

HAPPYDAN wrote:if it's a 2 stroker,

It is.
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
fly@AvSport.org
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US


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