Question422707-1510-01 18HP
I have a Briggs & Stratton engine in a lawn mower that runs fine for about 15 minutes (gets warm) under load or not, then res up and down then quits. It will restart but dies fast. Does this with & without gas cap. Internet search suggests to adjust valves. That option does not seem simple on this model. Any ideas on other possible problems/solutions?
AnswerSteve
If this Engine lacks power (possibly after warmup).
you may have these Possible causes:
1. Old gas, bad spark plug, very thick/dirty oil.
2. Choke is partially closed.
3. Carburetor needs adjustment or service.
4. Ignition not timed correctly.
5. Air filter is clogged.
6. There is a lack of lubrication.
7. Valves are not sealing properly.
8. Piston rings are not sealing properly.
9. Head loose or head gasket blown or damaged.
The coil can malfunction when it gets hot too. Check the spark when the engine is cold then hot.
When checking the clearances, rotate the flywheel and
watch the rocker arms, when the piston comes to the top,
and one rocker arm is closing and the other about to open,
then you need to rotate the flywheel one more revolution
to check the clearances. And a valve that was set at
.002, would not close fully when the engine gets hot.
On the other side of the coin, if the clearances are
too great, then the engine would be difficult to start,
as the compression release would not work.
