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.
#2
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.
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.
Is anything tapping the flywheel? It could be under it.
#8
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.
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 .
I have never seen this but here was the problem. The throttle shaft was broken not moving the throttle plate. I would start and run but not fast enough to deactive the compression release. Causing it blow back through the carb. Replaced The throttle shaft put the throttle plate back in. It cranked and ran fine. Thanks for all that posted.
#12
ILENGINE
Thanks for letting us know the fix. I have one customer with a rear engine snapper with a 8 hp briggs that has broken the throttle shaft 3 times.
I have never seen this but here was the problem. The throttle shaft was broken not moving the throttle plate. I would start and run but not fast enough to deactive the compression release. Causing it blow back through the carb. Replaced The throttle shaft put the throttle plate back in. It cranked and ran fine. Thanks for all that posted.
I got one customer that has two throttle and one choke shaft. I could see a throttle shaft wearing in two but not a choke shaft, but I now know it can happen. All three were in twin barrel Nikki carbs on Kawasaki engines.
A cheap way to see into the cylinder is a bore scope camera that connects to a smart phone- they can be found online for about $25 and it's only 1/4", so it will fit into all kinds of close spaces.
Seems like the first one actually wore in 2. The next 1 separated the throttle link plate on top of the shaft. The last one broke at the top throttle plate screw.
Put your finger on the joint between the engine and the body
You are feeling for relative movement between the two indicating loose mounting screws
A loose motor will cause a knock at low revs that disappears at high revs .
