Briggs knocking and low on power.

[hlw49]

Briggs 104M02-0005-F1 engine on a Snapper walk behind 12AVB2A2707 SER 1K195K31260. Customer brought it in and said it sounds like it is knocking and low on power. Sounds like the knock sound is coming from the carb. Any idea what it might be.

 

[ILENGINE]

Since OHV probably not a bad idea to check valve clearances. Also if the flywheel key is partially sheared and firing at the wrong time could be popping back out the intake into the carb.

 

[hlw49]

That's a thought I'll try it.

 

[slomo]

Water in the gas. Dirty carb.

 

[hlw49]

No not the problem clean carb and fresh fuel.

 

[hlw49]

Since OHV probably not a bad idea to check valve clearances. Also if the flywheel key is partially sheared and firing at the wrong time could be popping back out the intake into the carb.

Checked both not the problem.

 

[Craftsman Garage]

Is anything tapping the flywheel? It could be under it.

 

[Craftsman Garage]

If it were me, I would take everything apart down to the piston head to see if somethings got in there, and the piston is crushing it. If not, it could be something loose like the carb I would guess since it's low on power.

 

[bertsmobile1]

If it were me, I would take everything apart down to the piston head to see if somethings got in there, and the piston is crushing it. If not, it could be something loose like the carb I would guess since it's low on power.

Would not go that far but some detritus in the cylinder can do that like one of the screws from the choke / throttle butterfly
Same story with the cooling fan so worth while slipping the blower housing off and run it for a minute or so see what happens .

 

[hlw49]

Plastic carb no screws in the throttle of choke shafts.