QuestionI have a Bolens 4.0 Briggs push mower. I took it a few weeks ago for repair because it would rev up & down & he said it had water in the carburator & he removerd it & soaked it over night in cleaner...it was only 1 yr. old. It has been a few weeks now & is doing it again. I always keep it in the shed & it has never been rained on...am I getting bad gas? I noticed it started doing it today when I had just gotten new gas in the can & filled up & also when I tilted it up on its back wheels to mow up next to a tree. What is my problem? Please help I cant keep affording the repairman
AnswerAmy
Surging is almost caused by an air leak. Look at the carb mounting screws, carb plate mounting bolts or the carb mounting plate for cracks, If all these parts are ok then pull the fan shroud and look at the tube from the carb to the intake valve look for cracks or leaks. Replace the carb o-ring that seals to the carb to mounting plate if it damaged or missing..
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.
