Mower Backfired

[twfsa]

I attempted to start my rideing mower, the engine was cold and it backfired, it did start eventually after more than usuall cranking. I did not apply the choke but had the throttle wide open. I normally apply full choke to a cold start,and a couple of cranks its it fires up.

Now it seems that the engine is hard to start since the backfire, when cold.

The carburetor has a solenoid valve on the under side of the bowl that is supose to stop back fires when the engine is shut off. If you don't stop the engine in wide open throttle,( as the owners manual says) it will back fire.

Briggs 13 hp. 1 yr old.

TIA

Tom

[Jeff Wisnia]

You may have sheared the key holding the flywheel to the crankshaft and the flywheel has rotated from its designed alignment with the shaft. That will misstime the magnetic coupling of the flywheel magnets with the magneto coils and cause a weak spark at cranking speeds.

At least that would be the first place I'd look. Pull the flywheel and see if the key is sheared.

HTH,

Jeff

[Harry K]

Yes. It won't be completely 'sheared', just slightly nicked enough to throw the timeing off by the discription.

Harry K

[twfsa]

I called the repair shop today and he thought it may of blown a head gasket.I supose if the head gasket were blown that would cause the piston to not have the suction to draw fuel in on the pistons down ward stroke, thus makeing it harder to start.

If thats the case what cause the backfire.

Tom

[MC]

maybe the original backfire was caused by the same problem that is cuasing it to be hard to start now ?

The flywheel key would be the first to check , Of course a blown head gasket can easily be checked be doing a compression test.