Help Craftsman Lawn Tractor will not start, backfiring

13 years ago

I mowed my lawn not quite a week ago. Tractor started and worked fine. I have a Kohler CV15S Engine. I went to start the engine and the battery would not turn the engine over, weak. So I rotated the engine through its compression cycle by hand. Hit the starter again and a load of fuel shot out of the exhaust, I believe this was from having the egnition switch left on. It ran about 2 seconds and stopped. After that when cranking the engine did not sound right. I ran the battery down so I pulled it and charged it back. Reinstalled into tractor and at same time cleaned filter, so intake filter was off. Cranked engine and large flame shot out the carburetor.

I have read the forums and searched, but I have no idea what is going on with my engine. I checked many things short of rebuilding the engine and I no idea. Could it be 180 degrees out of time and how can this happen?

Any suggestions what it could be??? Very confused.

Comments (4)

tomplum
13 years ago
For some reason, the float valve let fuel though and flooded the engine- likely debris or a worn valve. SO now the engine is flooded and must be de-flooded. The spark plug must be removed- the carb serviced, likely the fuel system cleaned and the oil and oil filter changed. Remember that you are working with combustable fuel and use appropriate caution. Installation and use of an inline fuel valve will prevent this from occuring in the future.
zmanjohn
Original Author
13 years ago
Yes, I understand that. Everything has been changed. I pulled the head thinking that the valve seat might be been compromised. Cylinder looked good, no scores on piston wall and sealed from what I can see, cylinder looked better than most I have seen. I installed a new head gasket, reinstalled the head, pushrods and rockers, retorqued as per manufactures specs. Pulled carb and cleaned everything. The float seat was dirty, and the fuel solenoid was not working properly. Reinstalled everything and now get a large flame out of the carb. I also checked both valve seats while head was out and both valves were seated and sealed.
It appears that the timing is off, but I am not sure how this is possible, since from what I see from the service manual the lifters are driven off of gears. Even if engine was rotated backwords it should not cause a problem.
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baymee
13 years ago
It sounds like something happened when the piston tried to compress a solid fuel. The starter was turning the flywheel, which is keyed to the crankshaft and it abruptly stopped when the piston "hit a wall".

I'd check the key for partial sheering. It doesn't take much sheering to throw off the timing.
zmanjohn
Original Author
13 years ago
Baymee, Thank you so much your 100% right on. I would have never thought that this tiny of a key would hold the flywheel and crankshaft. It seems like soft metal, I scored it with a file. I know that the B&S engines I have worked on have a about 1/8" square key. Anyhow, thanks for the advise. You save me many hours of headaches.
Now onto the fuel problem, I am now searching for a rebuild kit for the carb. I think there is a local shop that has this.