Well, I believe it's probably not a good idea to try and troubleshoot the carb until the engine is broken in with the rings seated.

So we got a couple hours on the track for Saturday morning, and then we'll see if it still needs to have the choke on to run normal, if it still bogs a little at wide open throttle, and if it'll start without pouring gas in the cylinder.

Any one of y'all have a quality on-line reference for reading spark plugs?

 

Well, after a couple hours of track time, we have good power, no longer need to have the choke on to drive it, no bogging issues, but there is still one problem:

It won't start again after it's been shut off for awhile.

It will start if it has only been shut off for a few minutes, but after that it won't start. Doesn't seem to matter if the choke is on or off, it's apparently not getting gas. When I took the spark plug out it was dry.

1. Normally I would start with a compression check, as LT80 said, if it doesn't have good compression it won't 'suck' gas into the cylinder. But since it will start right after it has been turned off, I don't think that's the problem. Plus, it has good power when running.

2. I guess I need to pull the bowl off when it won't start and see if any gas is in it. I'm willing to assume that would be the case, since it will start within a few minutes of being shut off. However, where did the gas go that was in the bowl when it was shut off? And why doesn't it stay full? I mean, we do shut off the petcock after shut down, but the fuel line down to the carb still holds a tablespoon or two of gas... right?

The only scenario I can imagine is that all of the gas in the bowl and fuel line are flooding into the engine, and then that gas is draining down past the rings into the case. Whaddaya think?

Todd

 

I think fuel is flooding it.
The float/needle is a problem at times.
"gas is draining down past the rings into the case" sorta..Fuel is filling the bottom end but it goes directly in not past the rings.

 

Thanks LT80, I appreciate all of your experience. If the float/needle is allowing the bowl to 'overfill', shouldn't the closed throttle prevent the fuel from puking into the cylinder? Is there another way for the fuel to get into the cylinder besides the main jet?

Does the bowl get 'overpressurized'(?) and it forces the gas out the main jet?

It just seems like a pretty simple system, the passage down to the needle is pretty big, and it's obviously not plugged or anything anyway because it's allowing fuel to run through. Do I need to bend the tab on the float...?

Another thought is that, well, I replaced the fuel line when I put in a new in-line filter, the in-line filter is clear and so is the new fuel line. If the float/needle was allowing the bowl to 'flood', wouldn't that drain the fuel line? The nice thing about clear line is you can actually see if there is fuel being fed to the carb . A revelation.

If this problem is not correctable by me, it would be cheaper for me to buy a carb than take it to a mechanic, are those carbs for sale on evilBay for 69.95 as good as OEM? Thanks again

By the way, my daughter is happy, she does get to drive it, she just calls me when she wants to start it.

 

Jessie::
"There is no way that the fuel can seep into the engine, only if the needle and seat or float are not working."
Your correct. And it's not working properly.

"Gas can't leak through any jet unless there is an extremely high level of gas in your carb, but that will only happen if your bowl vent is plugged up."
Correct agaion with the exception that there is no bowl vent on a LT80 thus fuel goes into the motor.

FYI:: volumes have been wrote about the LT80 petcock and hydraulic pressure (the great debate as I call it) and I'm done contributing to that book.

Like you mentioned in a post, if the owner would shut the fuel off (get a inline shut off) and run it for a few seconds, this wouldn't happen.
Ppl don't understand that since forever on bikes or whatever, if you didn't turn your petcock off, fuel goes into the motor. They think the LT80 petcock should be perfect and they are far from it.

 

Hey LT80 and LT80Pilot,

I had the same problem after I finished up my rebuild on the KFX 80. I would have it running great, Idle perfect but when I shut it off maybe after 15 min. It wouldn't even crank over. The fuel did some how filled up the carb and when I started it sucked all the fuel into the cylinder and actually hydro lock the cylinder. I had to take the spark plug out and try to soak it up the gas before it went into the exhaust. But what I did was took the carb off and took it completely apart and found some crap in one of the jet that have all the tiny holes. But I also did take the float and needle out and cleaned that. I checked to make sure the float was working by blowing into the fuel supply and move the float to check for a seal. I bent the tag VERY little to to make it seal better. And that totaly solved my flooding into the cylinder prob. I also installed a inline shut off valve just incase. But its running perfect and haven't had a prob since.

 

"there is no bowl vent on a LT80 thus fuel goes into the motor."
To correct this:: There is a bowl vent but it's above the jets/intake.

Someone sent me a aftermarket carb. It has a steel tab for the needle.
As KFX80Dad mentioned, he adjusted the float tab and all is well.
The problem is:: 90% of LT80's out there have a plastic float tab that's not meant to be adjusted.

 

Gentlemen, thank you all for tolerating my long posts, and your thoughtful replies.

I had another 300- 500 word entry written, but I just deleted it, my understanding is this:

1. When you shut the fuel off, and let the engine run a little longer, is it critical for how long? I mean, you don't want to run it until the engine stops...?

That process only empties the carb, not the fuel line from the petcock.

2. Which way do you bend the little tab- toward the bowl, or toward the needle? (I do have a metal tab.)

I probably need to apologize for being such a pain-in-the-a$$. The learning curve is still pretty steep at this end.

 

No need to appologize! I'm sure we all are happy to help.
2)Bend the tab toward the needle.
1)I'd think that after the fuel valve is shut off, 30-60 seconds should do it.
If storing it, run it dry. Use stabil. Gas is soooo crappy these days.

 

So with the engine running, turn off the fuel, and wait for the engine to die, which takes 30-60 seconds? Or just turn it off with the kill sw/key after 30-60 seconds, even if the engine is still running?