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snowthrower engine throbbing


pjaffe's Avatar
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Join Date: Dec 1999
Posts: 507
OH

11-09-04, 08:15 AM   #1  
snowthrower engine throbbing

I have a Sears single stage 2 cycle snowthrower (model 536.884432, engine is Tech model #143.944571). It was my neighbors and sat in his garage for several years. I had to clean the carb to remove thick crud but it now starts nicely. The problem is that it throbs while idling. There is no carb adjustment screw that I can see. It also backfires occasionaly while idling. The carb looked pretty clean when I put it back together. I sprayed carb cleaner through every hole in the carb. There is a fuel filter that I also replaced adn the fuel seems to flow well to the carb.

What am I missing?

P.S. the backfire is a loud bang with white smoke and comes from the exhaust and not back through the carb.


Last edited by pjaffe; 11-09-04 at 08:18 AM. Reason: add details
 
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Azis's Avatar
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11-09-04, 09:05 AM   #2  
Azis
Hey Pjaffe,
I can't really tell from the parts diagram if your carb has a jet in the bowl. The nut that holds the bowl on the carb, if there is a screw with a spring that goes through the bowl nut, you can change your mixture with that. Try CCW 1/4 turn at a time to see if it will stop surging. Also the bolt is a metering device and has tiny holes or passages that must be clean. If not or if you have no screw to adjust, you should have an idle stop. You might be able to bump the idle up just enuff to get it to quit surging.
Also how does it run at throttle or when you throttle up?
At this point I think the backfire and surging are related, stop the surging and hopefully the backfire will cease as well.

 
pjaffe's Avatar
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Join Date: Dec 1999
Posts: 507
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11-09-04, 11:32 AM   #3  
no throttle

There is no throttle to control so it is only controlled by a linkage to some type of plate near the flywheel. It does run slightly better when I engage the auger. I will look at the screw in the bowl for adjustments and to make sure it is clean.

 
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