Won’t start

[otis71]

i have a 41 ULH that started then cut out and won’t start. Suspecting fuel I checked gas flow and cap vents. Bubble tested manifold, went through carburetor then swapped out carburetor with another one. Still nothing so I started to check the ignition even though spark was strong. Maybe under pressure it was not as strong? Cleaned, checked gap and timed points. Swapped plugs and even swapped coil for a NOS one. Checked that the timer wire didn’t have a short that rubbed when the timer was rotated. Strong spark but still won’t start. Checked compression and it’s good. Tried a small amount of gas in the cylinders and still nothing, then a shot of ether in the carburetor and not even a pop. I cannot think of anything else to check. Any ideas?

[joe fxs fxr]

If it won't start on ether, it's an ignition problem. I don't know what powers the coil on a ULH, but maybe that's the problem?

[duffeycycles]

bad gas & or flooded bad...propane torch burn the fuel out of the cylinders,start over
Don't ever put ether in your flathead

[T. Cotten]

bad gas & or flooded bad...propane torch burn the fuel out of the cylinders,start over
Don't ever put ether in your flathead

I wouldn't use ether in anything, Duffey!

('Xcept wasp nests...)

So, please explain how the torch is used?

Thanks in advance,

....Cotten

[duffeycycles]

plugs out touch the torch to the spark plug hole,burn out the excess fuel
If the crankcase is full of fuel,beware

[T. Cotten]

I'm trying hard, Duffey,...

To come up with a scenario where I would resort to that.

The best I can do is frantically trying to stage at the track.

Because there wouldn't be compressed air, I guess.

....Cotten

[KNUCK]

If flooded I would just pull the plugs and kick over a few times, put in clean plugs. Torch it out= boom! No pop with starting fluid then must be some kind of lost spark.

[T. Cotten]

Can we define "flooded", Folks?

Over enrichen the idle and it won't start, even if it isn't soaked with raw fuel.

If you are drawing raw fuel, two things are wrong.

(At least.)

....Cotten

[duffeycycles]

The torch is no more dangerous than leaving the plugs out near the spark plug hole,still attached to wires & kicking it over.I have been asked to help other shops that can't get bikes to fire under exact same circumstances.They have already tried the compressed air,no start.Quickly start after torch burns the excess fuel.This is common with late model sporty's after long winter.They will start run & die a few minutes later,or start run-shut off & not start again.I clear the fuel,suck the old fuel out with elect pump,put in fresh,drain the carb,new plugs & all is well.

[T. Cotten]

...I clear the fuel,suck the old fuel out with elect pump,....

Honestly Duffey and Folks,..

The only times (a few), that I suspected THAT much raw fuel on top of the pistons, it was because of a petcock leaking on garage-queen OHVs.

And just airing out was sufficient to start, however the lower ends were certainly full of fumes.

So the cause of the problem won't be gone by starting it, but its a start.

....Cotten
PS: I consider a wet plug "flooded".

[otis71]

So the bike is running good, is responsive but I’m still getting an occasional exhaust backfire upon hard deceleration. Will a little richer or leaner help solve that?

[T. Cotten]

So the bike is running good, is responsive but I’m still getting an occasional exhaust backfire upon hard deceleration. Will a little richer or leaner help solve that?

Usually that's a cold weather thing, Otis,..

So I would guess you have really really big exhaust leaks.

Assuming everything else is in order, of course!

....Cotten