Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! Is it one cylinder causing problem? Run cylinder test. Loosen spark plug wires and remove one at a time. If engine dies when one is removed, the opposite cylinder is not firing. With engine backfiring, it shows to me that you have an open valve when when the spark is occurring. You may have valve that is not seating, or bent pushrod.
So both cylinders are firing? Try loosing the exhaust, maybe it is plugged and is causing back pressure . Not often seen on four cycle engine, but it can happen.
Is the electric solenoid in the base of the carburetor opening when key is turned on? It has to have 12 volts as long as the key is on.??
Let me opt out, maybe someone else has idea!
Just a thought. How does the engine run with the air filter removed? It is possible that if you did not remove the air filter prior to turning the engine over that you have soaked the filter and it is restricting the air flow which would cause the problem that you are describing.
The engine was running fine until you flipped it over to change the seal right?
When replacing the top seal, you had to remove the ignition coils in order to remove the flywheel. What did you gap the coils at when reinstalling them?
This should be okay, but not all business cards are the same thickness and it could present a problem. Do you have a .010 inch feeler gauge? If so try resetting the coils with your feeler gauge. May not make a difference but it's the only thing that I can think of that might cause your problem unless the flywheel key is sheared and according to a prior comment you said that you had already checked that.
Did this make any difference?
Did you have to unhook or remove the throttle and choke cable when you removed the engine to replace the seals? Do you have one integrated cable or two separate cables?
If you had those unhooked, let's go back and look at those. Make sure that you have them hooked up to the proper levers on the engine and that they are adjusted properly. It's a long shot but it's the only other thing that I can think of that might cause your problem.
That was mentioned in a prior conversation with one of the other experts. You also mentioned that you had replaced the float valve in the carburetor. Is this correct?
The only other thing that I can think of is if you somehow have blocked the vent in the carburetor. This would cause the carburetor or over fuel and by turning the valve off you basically fixed the problem for a moment until the carburetor runs dry.
Give me a moment to check on one thing.
Can you provide the spec number from your engine? I don't see it in any of the prior conversation.
It will be FH601V- four or five more digits some being letters.