15.5 horse no start

Hey guys. I've gotten a tractor I'm fixing for my neighbor with a 15.5 horse b&s that won't start. The info I have is the tractor was stored for the winter, and when started in the spring it would "hiccup" and backfire. Eventually it just wouldn't start.
I've checked the spark, it's fine, has a new plug, and it's getting wet. Any ideas?
Thanks a bunch.

Make sure the fuel is fresh first. Bad fuel is bad fuel- even if it IS being delivered properly. Other things to check- Stuck float or junk in needle seat causing flooding, sheared timing key causing ignition timing to be out. You'll find the timing key between the flywheel and crankshaft.

Try removing the spark plug, and with the fuel valve off, cranking several seconds until any remaining fuel in the cylinder is expelled. Now, either squirt a teaspoon of fresh fuel into the cylinder and reinstall the plug -or- reinstall the plug and spray some starting fluid into the intake and try cranking. Report results.

Thanks Doc, the gas is all fresh, there was none when I got it. I was thinking about the timing (hence backfiring), I couldn't et the flywheel off tho.

We're going to take the carb apart fairly soon, I'll let ya know what I find in there. It did seem like a lot of gas. Could be old gas gumming up the needle.

Here's the issue. It's backfiring they the carb. Flywheel key is fine. I adjusted the valves too (probably a little too much gap tho). Any more suggestions?

Sounds like it needs a valve adjustment or repaired seats.

How would one go about doing this? I did attempt to adjust the valves when I had it open.

Flathead or OHV?

It's ohv. The springs seemed pretty tight. Seems the intake may be open on the compression stroke. But I have no evidence, an it doesn't really explain backfiring.

The thing is, it has decent (100) compression. If it where a valve seat, I would expect it to be lower.

Hmm maybe a bad coil. Even tho its getting spark it might not be getting enough, sounds like you went through a lot of the trouble shooting questions.

Ya I tried almost all I could think of. The spark is blue. The only conclusion I have come to is it's not igniting during the right stroke. It's a 4 stroke, so the motor spins twice before igniting.

BlackMountian88 wrote:

Ya I tried almost all I could think of. The spark is blue. The only conclusion I have come to is it's not igniting during the right stroke. It's a 4 stroke, so the motor spins twice before igniting.

Right. Except- These engines fire on EVERY revolution. It's basically a waste-spark system. It's easier and cheaper to have it fire on every revolution than to try and make it NOT fire on the exhaust stroke.

Has this engine ever been fully or partially disassembled? It's starting to sound like the valve timing is off, possible if the camshaft was reinstalled incorrectly.

Precisely my point! No it's not been dis assembled. I had it running earlier. It was running real fast, then died when I turned the throttle down. Bit I think this is a different problem.

So it surged? Your governor might be fried and stuck open/losed.. ausing the engine to flood out.

No not surging. But I do think I forgot to reconnect the linkage spring.