Tecumseh 10HP backfire through carb

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  #1  
Old 01-07-09, 05:39 AM
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Tecumseh 10HP backfire through carb

Hi all,
Old Tecumseh 10 HP (hh 100) on Ariens Snowthrower (not original engine). Got ready for winter in November, ran fine. First snowstorm, started and ran about 10 minutes.
Now backfires through carb. Keeps breaking flywheel keys. I have replaced the flywheel key 3 times. Has 125 lbs compression. Valves seem to work okay when looking through sparkplug hole. Has internal ignition (points under flyweel), point gap .020.
Timing?
Backfires through carb badly, I'm afraid of it blowing up.
Any ideas?
Thanks
 
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  #2  
Old 01-07-09, 06:25 AM
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Join Date: Jul 2006
Location: Central New Hampshire
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Breaking flywheel keys is extremely rare on a snowblower. You may have valve timing problem.
 
  #3  
Old 01-07-09, 07:28 AM
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The only time i've seen that is when an engine throws a rod, it required a huge amount of force to shear a metal key. I've read that the keys look similar but are different and will fit both external coil with points and solid state. Using the wrong key will cause a timing issue. Triple check the part you are replacing with where you are getting the parts from.
 
  #4  
Old 01-07-09, 08:01 AM
Join Date: Jan 2007
Location: MA
Posts: 514
I would set the timing according the the procedure outlined in the Tecumseh service manual, it is on page 68. Also, when you have replaced the flywheel key 3 times, what did you torque the flywheel to upon re-installation? It should be 52.5 ft. lbs. Also if you used any lubricant to help remove flywheel be sure you have completely dried all of it off. A loose flywheel can ccontinually shear the key.
 
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