high speed surging

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  #1  
Old 01-09-09, 08:23 AM
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high speed surging

hi i have a ariens snowblower with a 4hp tecumseh. it runs smoothly until i engage the auger and drive wheels. i have cleaned and rebuilt the carb, the only thing is the float seemed to be a little high so i lowered it. would a low float cause the engine to starve once the load is put on it?, i'm thinking that once the load is put on it the fuel can't quite keep up, does this sound reasonable?
thanks
steve
 
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  #2  
Old 01-09-09, 08:37 AM
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Post the engine model number, etc.

Problem is very likely a dirty carburetor but could be governor related. When cleaning a carburetor every passage, nook and cranny needs to be cleaned thoroughly.

Here is a link to a Tecumseh service manual that may apply to your engine:

http://www.cpdonline.com/692509.pdf
 
  #3  
Old 01-09-09, 01:41 PM
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How did you clean it? Did you soak it in a carb cleaning solution for at least 2 hours?
Float should be set to be paralell with the bowl flange when the cab is upside down. Remember, when working on the carb upside down, what appears to be high is low and vise versa.
Did you install new parts?
 
  #4  
Old 01-10-09, 07:51 AM
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hi i did soak it, then i blew it out and i even did a smoke test to make sure all the ports were flowing freely, it has new high and low needles and float needle and seat. when i reassembled it the float looked like it was tipped up too high (towards the carb base so i slightly bent the tab and it did look parrallel to the base when i was done.i am just thinking that maybe if it was too low that maybe it was starving for fuel when i engage the auger and drive for lack of fuel flow causing it to do this surging, does that sound possible?

Also sorry i don't have the number off the engine as they put the starter button assembly right on top of where it is stamped in the recoil housing and of course it rusted directly beneath it, i can get about the first 4 letters i know its a horizontal shaft small frame
thanks
steve
 
  #5  
Old 01-10-09, 09:51 AM
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If your engine is a Tecumseh 4.0 HP L-Head 4-cycle Horizontal, it may be a model HS40. Look at the manual I referenced in an earlier post. See if you can identify your engine and carburetor from illustrations in the manual. The manual shows how to correctly set the carburetor float using an 11/64" (4.36 mm) drill bit.

If you carburetor had a welch plug covering fuel passages, did you remove the Welch plug and clean behind it?

The Tecumseh service manual states, “After careful disassembly of the carburetor and the removal of all non metallic parts, the carburetor body and all other metallic parts should be cleaned with solvent, or commercial carburetor cleaner, no longer than 30 minutes. Use compressed air and soft tag wire to clean internal carburetor passages. To do a proper cleaning job, the welch plugs must be removed to expose the drilled passages.”

In my opinion and from experience, in addition to what Tecumseh recommends, chemical submersion cleaning of carburetors should only be performed in cases where the carburetor is severely varnished and should be followed by cleaning with an aerosol carburetor then blown out with compressed air.
 
  #6  
Old 01-11-09, 05:43 AM
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Pay particular attention to page 20 of the manual Airman ref'd, the fuel bowl retaining nut, I cleaned an H35 carb yesterday that had I not known about the idle fuel passage in the groove a the top of the nut, I never would have seen it.
Making sure all the holes in this nut was clean, the engine ran great.
hope this helps,
thanks
 
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