Briggs &Stratton Has Slight "Pop-Pop-Pop" When Running

A

ABrosz

Forum Newbie
Hi and Hello:

I Love this forum. My Briggs & Stratton 26-year push lawnmower just developed a slight "pop-pop-pop" when running. This is hardly noticeable, but the mower feels like it also does not have enough power. It does cut gas. Model series is 9000-10000 according to the user manual. It is a pull start, and 4.5 HP. Carb has no adjustments, and I must prime the carb 3x before starting with RED primer bulb. Is this fuel delivery? Magneto? Worn rings? New spark plug?

Thx in advance. Great help and experience with the members on this forum.
 
After 26 years I suspect that it is floating the intake valve and is not sealing. Over time the valve face and seat wear which results in the valve clearance getting narrower until it can not longer close the valve.
 
ILENGINE said:
After 26 years I suspect that it is floating the intake valve and is not sealing. Over time the valve face and seat wear which results in the valve clearance getting narrower until it can not longer close the valve.
Click to expand...
ILENGINE:

thx for the fast replay. I guess a compression check would show me more...right? New valve or is the seat that is probably the problem?? Mower is actually 35 years old, not 26 as I stated above. Can I buy a short block or maybe on Ebey see what is available. I really can't afford at this time a new electric mower but maybe bite the bullet/

Thx again.
 
Compression test is not a good test for those style engines. Leakdown testing is the better test. Would tell you if you have compression leaks and were. With that age I would just remove the head and take a look at the cylinder walls looking for wear and a ridge at the top of the cylinder walls to get an idea of wear. Also if you close the valves which should be stlightly past TDC power stroke and then take you thumb and push on the top of the valves and see if you can rotate them.. I suspect all minimum the intake will turn with very little effort.

New valve may be needed but most likely valves will need to removed and have the stems shorted to reset the valve clearances and then the valve seat and faces lapped back onto proper contact. Proper way would be to cut the valve face and seat with a valve cutter set.

Most likely new short block in no longer available, and if it was would cost more than a new OHV engine with factory warranty.
 
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