Backfires when trying to start

[Joe_126]

So, I was having trouble getting my mower to start (hard to get it to crank over due to valves being out of adjustment i discovered). While i was at it I changed the air filer, spark plug, and changed the oil. When i try to start it, it turns over easy now but cranks forever and will backfire a few times before it takes off running.

I have taken it apart and redid the valve adjustment 4 times total and made sure that it's right. I didn't have any problems with backfiring before I did it, and once i got enough juice to it to get it to crank over it started relatively easy. Is it possible that i have a bent pushrod or something that wasn't noticable because the valves were so loose?

 

[bertsmobile1]

A blown head gasket is more like it
Then the backfires can cause the flywheel timing key to break so it is then out of time

 

[VegetiveSteam]

Did you adjust the valves with the piston at TDC? If so were you on TDC compression or TDC exhaust?

 

[PTmowerMech]

Backfiring is fuel being burned when the exhaust valve is open.

Does it black smoke at all when you're using it? If so, it could be the carb is too rich.

 

[Joe_126]

******Update******

I had replaced the coil a couple weeks ago and last night while talking to my Uncle he said it sounded like weak spark. I used his trick of using the side of an aluminum can to allow the magnets to suck it up, then tightening the coil down and removing the can. It worked. Starts easy now with no backfiring and starts off the key without needing a jump box for extra juice. These old timers are worth listening to. Lol

 

[sgkent]

******Update******

I had replaced the coil a couple weeks ago and last night while talking to my Uncle he said it sounded like weak spark. I used his trick of using the side of an aluminum can to allow the magnets to suck it up, then tightening the coil down and removing the can. It worked. Starts easy now with no backfiring and starts off the key without needing a jump box for extra juice. These old timers are worth listening to. Lol

did you originally set it to ,010 with a brass feeler gauge, or the plastic tool? An aluminum can is about .004" - .007"

 

[Joe_126]

did you originally set it to ,010 with a brass feeler gauge, or the plastic tool? An aluminum can is about .004" - .007"

No, when i put it on I just guessed at it.

 

[Joe_126]

No, when i put it on i just guessed at it. On second inspection, it was a pretty good gap.