Carb Adjustments- Please Read - Snowmobile World : Your #1 Snowmobile Forum
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post #1 of 4 (permalink) Old 12-07-2005, 11:34 AM Thread Starter
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Does anybody know the float adjustments on the carb of a 1989 yamaha srv?
I think that's whats wrong with it, when i punch it and give it gas and then let off a little and than punch it again it will stutter and backfire. im not sure whats wrong. i recently rebuilt the motor and carb, it has boyesen reeds, aaen single pipe, k&n air filter and 150 main jet and 92 slow jet. it seems to run fine and plugs look great light brown/gray color. any ideas? anything is greatly appreciated. thanks!
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post #2 of 4 (permalink) Old 12-07-2005, 08:42 PM
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you took out the breather box and slapped on the k&n didn't you???? that's the problem.....drop the k&n and put the breather box back in. You can't start putting aftermarket parts on and expect it to run well in all situations. Basically, you've set your sled up for drag racing. So's ONLY good for 1000 ft races......
You change the pipe....the surface area of metal changes.....which means the exhaust pipe temp changes.....which means the vacuum pressure changes.....well......your bore and stroke are designed to burn a certain mixture and measure of fuel/air, and now you're playin with the air by changing the reeds and exhaust.....then you increase the jetting to add more fuel to compensate for the extra air flow through the system......but guess what.....your displacement is still the same.....therefore, you're basically sending in too much fuel and air for the engine to burn properly, causing problems.............. Now you either have to put your stock parts back on, or bore your jugs and slap on some oversized rings.
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post #3 of 4 (permalink) Old 12-08-2005, 02:36 AM
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Current sled 01 ZR 700 X
3.5 Oles Machine riser,1.25 ripsaw,388/389 rear springs,45deg hooks,Shell Utra Oil

Previous sleds
-69 Dauphin--71 SW 396--75 GPX338--85 Safari 447--87 Safari 377
89 Safari Scout E--84 SRV 540--86 SRV 540--91 Indy 500--87 Indy 400
2nd 91 Indy 500
--95 STX 583-- 01 ZR 600 VEV
Current weather in Chelmsford
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post #4 of 4 (permalink) Old 12-09-2005, 09:51 AM
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SW actually has a couple of GREAT tech articles relating to the importance of exhaust pipe temperature and airbox temperature, and how they affect engine performance.
Click here:

Pipe Temperature and Airbox Pumping

Airbox Temperatures

I really think these 2 articles are imperitave for a "backyard mechanic" to read, as they discuss things that the salespeople of aftermarket products will NEVER tell you.
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