10 Hp Tecumseh Engine backfires


Old 12-11-03, 04:50 PM
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Question 10 Hp Tecumseh Engine backfires

I recently took out my Sears snowblower for the season and it exhibits the following problems.

- Engine is hard to start by hand, I often resort to the electric starter.
- It backfires ocassionally.
- When I use the primer bulb and start it by hand, quite often the engine yanks the cord out of my hand violently. It pulls it inwards.

My engine is a Tecumseh HM 100 series, 4 stroke, solid state ignition with a type 3 carburator.

I have consulted the "Tecumseh's Technicians handbook for 3 to 11 HP "L" head engines". I have the done the following.

1) I have checked the ignition assembly gapping with respect to the flywheel.
2) I cleaned the carburator and set the mixture screws to the default setting as per the manual.

Is this a dirty carburator problem, ignition problem or sticky intake valve?

If it is a sticky valve, how do test it ?

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Old 12-11-03, 09:41 PM
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Hello Zman!

The kicking back problem sounds a lot like a sheared or partially sheared flywheel key. That would also explain the backfires. Also make sure the drive belt is not too tight when trying to start. If it is engaging when it shouldn't, it could jerk the cord out of your hands.
Old 12-12-03, 07:33 PM
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Hello Cheese,

Thanks for the suggestion.
I pulled off the flywheel and the flywheel key is intact.

I took another look at the manual and found they talk about an unusual device on the camshaft gear. They mention a compression release mechanism that keeps the exhaust valve open to facilitate starting (by minimize compression) and when the engines starts, the centrifugal force moves it out of the way and allows the exhaust valve to operate normally.

Could the improper operation of this device be causing my problem ??

Old 12-12-03, 07:48 PM
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Its a Posibility. However I would check that device out and make shure it is performing to specs suggested in your operators manual.
Old 12-12-03, 08:30 PM
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About three years ago Sears had a problem with the snowblowers kicking back like you described. I believe there is a Sears Service Flash correcting this problem. Call your Sears Service Center and give them your model number and ask if they could check on the Service Flash. They may not want to give you the information with out them working on it. Good luck.

Old 12-13-03, 12:01 AM
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The compression release malfunctioning is possible, but not very likely. Check sears like roger mentioned, sounds like he's on to something.

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