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PostPosted: Sat May 05, 2007 6:23 pm 
Still on the Trailer Member
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Joined: Sat May 05, 2007 5:45 pm
Posts: 1
I have a 2001 Yamaha Breeze. It just recently started to pop through the carburetor and wont stay running (without revving it and then sometimes dies). The engine idle is not stable. After warming up, it will only start if the choke is on. After revving the engine sometimes it quickly drops to idle, many times stays on a high idle for up to 20 seconds more before dropping. I'm not sure if there is supposed to be pressure at the cylinder head chamber (round cover with black hose to air box), but when it's running there is pressure coming out the hose. The pressure is behind the round cover by the (2) round tappet covers on the cylinder head. I've had quads/3 wheelers for years and have fixed several problems but this one has really got me stumped.

Things I have done/checked:
1) new gas
2) new plug
3) remove carb, cleaned it, and check pilot setting (2 and 1/2 turns out)
a) float operates fine
b) needle shuts fuel off and is free from deposits
c) cleaned with carb cleaner and compressed air
d) checked float level
4) checked for air or vacuum leaks
5) Check valves setting
6) checked timing chain and tensioner
7) checked top dead center marks on stator and camshaft
8) checked compression (140 psi and no drop)
9) pulled spark arrestor and ran engine w/o it

I don't believe it's a problem with the valves or piston rings becuase of the compression checks fine.

I don't know what else to check or try. Please help!



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PostPosted: Sun May 06, 2007 5:29 am 
Still on the Trailer Member

Joined: Sat May 05, 2007 4:22 pm
Posts: 6
Did you run a fine wire or small drill bit thru the jets when you cleaned the carb, because it sounds like the pilot jet is plugged? However, if the tiny passageways in the carb body are also plugged, a repeated soaking in carb cleaner and blow-out of those passages may be required, and if they are plugged bad enough, even that won't get it out. A new carb may be required.
Might try covering part of the air cleaner with a plastic bag to see if it will idle.
If it does, the problem is in the pilot circuit.

Did this quad sit for a long time?

The crankcase vent should not have pressure on it, but you say it doesn't leak-down and has good compression, so it doesn't sound like that is the problem. That hose should have a slight vacuum on it to suck vapors into the airbox from the crankcase. Pressure there usually means leaking rings.

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