# 10 HP Tecumseh backfiring



## JerryJ (Jan 11, 2012)

I'm trying to help my son that took on a job, working on a coworker's machine.
It's an older machine but have replaced a few parts and it's slowly returning to super condition.

One problem we had was the engine would backfire through the carb during start-up. It might run 2 or 3 seconds then die.

New points and condenser, set at 0.020" and cleaned with a business card to eliminate debris on the contacts.
We backpeddled the crank to 0.090" inch, c/cw and then clockwise to 0.080" to set the timing, with referrence to the make/break contact of the points.

The valve lash is 0.008 intake, 0.011 exhaust, both valves were lapped.
The carb was unltrasonic cleaned. New plug 

One thing we found was during the startup, when we choked it, we found that extra priming of that primer bulb allowed the engine to start more readily and would NOT catch without that process. 
But it back fires through the carb (flames can be seen) and then she dies.

To me it smells like timing, but if the timing is correct (so we think) what else could it be?


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## CarlB (Jan 2, 2011)

Either the intake valve is not closing properly or the timing is too far advanced. Pretty much those are the two possibilities for backfiring through the carb. Retarding the timing would be my first step. Also check the point gap if that is not correct it will also cause problems. Set the gap first then set the timing.


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