4.5 hp tecumesh two stroke wont start

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  #1  
Old 12-30-13, 03:21 PM
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4.5 hp tecumesh two stroke wont start

Hi,

Never had many issues fixing a two stroke.

This one has an excellent spark. The carb is like brand new. I get gas when I prime it. I have also sprayed some quick start on the carb.

When i turn it over, it will only backfire. Never once has it started.

Cant understand this. Strong spark, fuel on plug tip when I remove it.

Is it possible the flywheel key has been sheared off on a single stage thrower?

I would have thought that the belt would slip if the auger hit a chunk of ice or something.

Have not seen this before. Any thoughts?

Thank you.
 
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  #2  
Old 12-30-13, 03:33 PM
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If you had thoughts that the flywheel may have broken a key you can test for that.

Remove the spark plug. Using a pencil or something thin like that find when the piston is close to the spark plug hole. The spark plug should fire when the piston is close to the top of the cylinder on every other upwards travel of the piston.
 
  #3  
Old 12-30-13, 03:45 PM
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DO i plug the plug into the wire while im checking with a pencil to see if the piston is at the top of the cylinder? Id have to be timing and seeing a spark at the same time I see the piston at the top of the cylinder. Seems difficult to do. Should the plug not fire on every upstroke of the piston? I thought on a two stroke it fires every time and on a 4 stroke it is every other stroke.

Thank you.
 
  #4  
Old 12-30-13, 04:21 PM
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Sounds to me like the flywheel key is sheared. Have a good one. Geo
 
  #5  
Old 12-30-13, 05:40 PM
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Yes Geo, i think this is the case. Ill pull it apart on New Years day. These are such a PITA to get into and take off the flywheel etc. Got to fix it. Must be only 2 years old this snowblower.

Thanks.

Ill update later.
 
  #6  
Old 12-30-13, 06:12 PM
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Make sure you remove the flywheel to check the key, Tec engines are deceiving if you just look down om the key after removing the flywheel nut, they might look ok from the top but are sheared down below. Have a good one. Geo
 
  #7  
Old 12-30-13, 06:18 PM
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In case you weren't aware, the easy way to lock the engine to remove the nut on the flywheel, remove the spark plug and load the cylinder with small rope like starter rope, leave a little hang out, when the piston tries to compress the rope the engine locks and nothing gets broken. Have a good one. Geo
 
  #8  
Old 01-13-14, 05:52 PM
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Update:
I took off the cover of the flywheel and took off the coil.

The flywheel spins freely. Im not feeling any resistance when i spin the flywheel.

This must mean bigger problems than the flywheel key sheered off. I can also see the flywheel key and it looks inline with the flywheel where it should be.

Thoughts?
 
  #9  
Old 01-13-14, 08:29 PM
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There must be some resistance. In your first post you said it was backfiring.
 
  #10  
Old 01-14-14, 08:41 AM
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Tecumseh flywheel keys are deceiving and cant really be checked without removing the flywheel, check the pics below for reference. Have a good one. Geo
Here it looks ok:


However OOps:
 
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