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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › YS91-SR Poor Running
08-30-2013 11:00 AM  5 years agoPost 1
mister-j

rrNovice

Ponty, init butt

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I've got some issues with a hard to tune YS91SR, optifuel 20%, os#8.

Its had new bearings, new gaskets, new o-rings, new reg diaphragm and a complete rebuild.

It was running fine then started acting up one day, which lead to the bearing replacement. Since then it just won't run unless the needles were super rich.

I've richend out the reg to allow me to lean out the main needles to something remotely close to the factory, but still runs awful, hangs on the pipe bad, won't idle.

Idle - 1 turns
High - 1.5 turns
Mid - 2 turns

These are the best settings I can get it to run at safely.

I've noticed that on the mid needle there is a what appears to be a machined groove on the taper. I've not seen this on other needles, OS etc.

Is this groove factory, or damage? The groove is very shallow, you can catch it with a finger nail. The mid needle doesn't have a groove but is marked.

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08-30-2013 11:48 AM  5 years agoPost 2
MXRACERX43

rrApprentice

Hazleton,PA USA

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The check valve is installed in the correct orientation? Tank is holding good pressure when checked 15 mins or more later?

Team Miniature Aircraft~Team GensAce

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08-30-2013 11:52 AM  5 years agoPost 3
mister-j

rrNovice

Ponty, init butt

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Check valve is good, whole fuel system holds pressure perfectly.

I Can leave it pressurised with the line clamped for a good few hours.

My concern is that if the needle is damaged, even with a little step in the taper, it could make a huge difference in the fuelling.

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08-31-2013 01:33 AM  5 years agoPost 4
crflyer

rrApprentice

Maine

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The needle valve needs to be replaced,also make sure you don't have an exhaust leak.

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09-13-2013 06:55 AM  5 years agoPost 5
mister-j

rrNovice

Ponty, init butt

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Just to update this thread, a new mid needle sorted the issue. The damage to the taper must have been right in the sweet spot on the needle.

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