Snow blower engine ramping.

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  #1  
Old 04-17-08, 03:30 PM
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Smile Snow blower engine ramping.

I have a snow blower with a Tecumseh 8 hp engine. It starts great, but after it runs about 20 minutes it begins ramping in RPM and eventually goes so low on the low end of the ramp that it stalls. Once that happens, I basically have to go back in the house and have another cup of coffee. When I go back out, it will start and run another 15 or 20 minutes.
I was told that old gas was the problem. I got fresh gas and that helped two years ago, but now it is getting cranky after 20 minutes even with fresh gas. Enriching the mixture by choking it some doesn't help so maybe it's running too rich. However, I can not find a needle valve on my engine to try to lean out the mixture.
I also replaced the spark plug so please suggest something other than that.
Moving South is an acceptable suggestion :-)
 
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  #2  
Old 04-17-08, 04:29 PM
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You might clean the fuel tank just in case it has a lot of dirt floating around then,
Clamp off the fuel line, remove the carb bowl, release the clamp to see if you have good fuel flow to the carb, raise the float to see that it shuts off the flow with minimal pressure, clean the junk from the bowl, clean the bowl nut, 2 holes close to the bottom and a tiny one about midway up(I usually use the wire from a twist tie), spray all holes, cracks and crevases with brake parts cleaner, reassemble and you should be good to go. If this didn't work it will be probably be necessary to rebuild the carb. If I missed something one of the real mechanics will post to help further. Refer to the photo below. Have a good one . Geo
http://i190.photobucket.com/albums/z...c_bowl_nut.jpg
 
  #3  
Old 04-17-08, 11:23 PM
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Surging is usually due to a lean condition, so along with Geogrubbs advice, I would also suggest making sure the flow of fuel from the tank to the carb is ample (fuel lines can swell on the inside, and restrict flow, or the filter could be clogged, or trash in the tank). Also, Loosen the gas cap and see if that helps. If so, the vent in the gas cap is clogged, and allowing a vacuum to develop in the tank as fuel leaves with no air entering to replace the volume.
 
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