MTD 8 HP snowblower backfires & surges

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  #1  
Old 11-29-05, 07:08 PM
surfingharley
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MTD 8 HP snowblower backfires & surges

I've owned this MTD since new (5-8 years). Its an 8HP (Tecumseh?) engine is now backfiring and surging, the choke must be left on or it will die, even when warm, and throughout the RPM range. This symptom has been getting worse the past 3 years, now its pretty bad - I can see the exhaust valve glowing through the muffler (probably normal) and explosion flashes during backfire (not! normal).

I was thinking gum in the fuel system (might have missed the fuel additive at a season's end) or a lean mixture, but the backfire makes me think timing.

What say you? Is timing adjustable on these engines? Do I need to provide more specific engine info? (where is the label?)

Thanks in advance for the good advise
 
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  #2  
Old 11-29-05, 09:50 PM
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timing is pretty much not adjustable, you can take the flywheel off and check the flywheel key, could very well be it. as for the carb.... if it was left sitting for a long time without treated gas, could very well have gum deposits in it, might be able to look at it to see some.
 
  #3  
Old 11-30-05, 12:33 AM
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Yup, you need to clean the carb. The lean fuel mixture is causing the backfire and hotter-than-normal exhaust.
 
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Old 11-30-05, 08:08 AM
surfingharley
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Is carb cleaner an option?

What is the consensus on running carb cleaner through he machine? Is that worth a try or should I just plan on rebuilding the caburator?

Thanks, and -- you guys are fast!
 
  #5  
Old 11-30-05, 02:37 PM
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If you have moderate to heavy varnish build-up then spray cleaner won't touch it. You will need to soak the carburetor in a quality bath-type cleaner (I like NAPA #6401). If the varnish is light, flakey build-up then a spray cleaner may work well enough. I think the former will be your case though and therby warrant a good soaking and reconditioning with the correct Tecumseh kit. Post back with engine ID #'s and we'll provide you with part numbers which you can pick up at your local Tecumseh dealer.
 
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Old 12-01-05, 12:33 AM
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I assume you mean a carb cleaning additive that you put in the gas? If so, don't waste the money. It won't work, regardless of what the can says. You'll need to go ahead and drop the bowl at the very least and clean the carb, possibly having to soak the entire carb in a bath type cleaner like Puey suggested.
 
  #7  
Old 12-01-05, 04:27 AM
surfingharley
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Engine ID

I figured it would be a carb cleaning job v/s something as simple as gas additive.

This is a fairly new machine, haven't had the shrouds off yet. (and I misplaced the engine manual)

Where should I look for the engine ID?

ps. This site is a great find!
 
  #8  
Old 12-01-05, 01:37 PM
generalsecord
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8hp tecumseh

after numberous attempts at rebuilding the carb,i finally broke down and bought a new carb from jacks small engine it was only 58.98 includeing s/h.so i will try one more time at rebuilding the old carb as a back up.whats the best snowblower engine out there.when i was the small engine mech.at parks and recreation we swore on briggs and stratton.i retired 4 years ago and i dont know whats the best out there
george
 
  #9  
Old 12-01-05, 08:51 PM
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swear one briggs myself. only one to let me down had a failing coil. briggs, kohler, honda, kawi are all good ones.
 
  #10  
Old 12-02-05, 06:02 AM
generalsecord
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8hp tecumseh

ok thanks for the info i will keep that in mind when i purchase a new one
george
 
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