fuel issue

[dseuser]

I've got a '78 KE100 which was sitting in my dad's shed for most of its life. I rode it as a kid and now and trying to get it going again. It runs fine for the first 5 minutes, then stalls out. When I squeeze the fuel line, I see gas I can, but it is not completely full from top to bottom. Not sure if it should be or not.

After I restart it, it will run for a shorter period of time, then stall out again. This repeats over and over. Sometimes when I restart, the engine revs way too high. Idle speed is a little too high too, perhaps unrelated.

I've dumped the fuel tank and checked the screen in the petcock, which is always clean. Seems to be more related to something being hot and impacting flow. It has a new plug as of last winter, and fewer than 20 miles since then.

I had it in the shop last fall, for starting issues, and it worked great afterwards. The dealership does not want to touch anything this old because of scarcity of parts.

Any suggestions of where to start? Does this seem like a float issue?

Thank for any ideas.

[kawpaul]

Could be the coil breaking down. I would check that before I went any further with the fuel system.

[mcegans]

How long after it stall does it take before you can restart? Right Away or do you need to wait? If so how long?
Coil could be opening when warm and have to cool or you have a fuel delivery problem. Running the carb bowl empty before it can replenish itself.

[dseuser]

After it stalls, I can usually start it in 30 seconds. Not sure if it takes longer with each start afterwards or not.

Not sure if this has any impact or is a red herring, but my battery is dead. This bike can run without a battery though. I bought the battery this time last year, but I don't have a trickle charger. When I rode it 30 years ago, 12 months was normal life of the battery.

This evening I got it to run for one block, and then it died. I could not get it to start again.

I'm thinking I should unscrew the spark plug and look for spark as I crank. I don't have any test equipment, but on this old bike, there just can't be that many variables to rule out.

I did notice that the carb intake has a small leak, which I will try to seal externally. Looks like it was replaced with a copper tube, which has a small split.

Thanks for any advice.

[mcegans]

I would think if the coil is opening up that 30 seonds would not be long enough to cool it but a spark check would confirm this. If you can as soon as it stalls check for spark
An intake leak on a 2 stroke is a definite issue. I would try to seal that up even if it means getting a new intake boot.
check fuel flow to the carb If you have good flow then a carb clean up is needed. I think once you have used up the gas in the bowl it stalls and you need to give it time to refill. Take the carb off and soak it in solvent. Blow out the main inlet needle and seat.
A quick test to see if the needle is opening is hold the carb upside down with float and bowl installed and blow into the fuel inlet. You should not be able to pass air, the needle is seated. Then turn carb upright and blow into inlet again air should go. Use your mouth on a clean piece of hose for this you will feel if the air will pass. Don't blow in there with a compressor except with the float and bowl removed for cleaning.

Clear as mud??
Tom

[ratvespa]

one thing with old 2 strokes, especialy if they have been sitting a long time, is the crank main seals will go out. either it will suck air from the dry side and have an eratic idle and running problems, or it will suck oil from the gear case and smoke a ton (will also cause running problems). but I would check all of the stuff like people said before. but having owned many old 2 strokes, and many that were sitting for years before I got my hands on them, I got in the habbit of just changing the seals so that would be eliminated.

[Kawasaki_Boy]

i agree with the rest, check spark. also, take out the carb and make sure all the jets are cleaned and you can see through them. blow the jet lines out with compressed air to make sure there is no crud inside the carb. make sure the float valve is opening and shutting, sealing the fuel off when the floats rise etc. this might not necessarily be the problem, but it is easy to do and would be nice if it was the fix, plus a clean carb is always good peace of mind.

[stratgooroo]

yea i would definitely check spark like everyone said but i dont think that would be the problem if it will start and then die because with no spark it would not start at all. also like was said check the carbs because it seems to me like some sort of fuel issue...if it's a two stroke this is a no brainer but i would say to make sure that the fuel mixture is correct also.

[Bill Frazier]

Have you checked to see that the gas tank vent is OK? A clogged vent can cause fuel starvation.
Open the fuel cap and see if it will restart at once.

[LivNowPayL8r]

I'm with Bill F... start simple! Only move on to more complex issues (crank seals, etc.) after all the basics are confirmed.