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Discussion Starter #1
Lately I got quite weird problem with engine. When it is cold it starts and runs without any problems. I can go 100kms without any problem. But as soon as I stop (turn off engine) e.g. for fuel it is not possible to start the engine again. It is dead completely. no a single puff...
I have to wait 30-40 minutes for engine to cool down and can start it again. When it starts it runs without any problem again till next turn off.

I checked the spark - yes it is there. Blue.

Bike CX500c 1981
 

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Discussion Starter #3
I checked the spark - yes it is there. Blue.
Spark plugs are not wet and over flooded. Electrodes of spark plug are light brown.
 

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Sounds normal enough.

But .... make sure the chokes are returning to open.

Next time, try removing the air filter to see if it will start.

Have you checked the valve clearances?
 

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Discussion Starter #5
Yes, I tried choke open/close in various positions. I'm having 30 mins for experiments on every stop :)
I didn't check valves. Can try.
For me it seems very strange to have it working/non-working so strict. There is nothing in the middle. Engine has no problems while it is not turned off. Once it is off, it is dead while not cool again.
 

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A long shot : Defective Main fuse ? Conductivity impaired because of age and metal fatigue when hot ?
 

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I had the same issue with my 1992 Renault... (yes, it is a car and has 4 wheels & 4 cylinders, and this is a 2 cylinder / 2 wheels issue. thank you).

It turned out that the carburettor middle did not seal at the right level (or did not seal at all) and the carburettors became flooded. That didn't heart when the weather or engine were cold as reach mixture is always good for cold starts, but, it made it nearly impossible to start the warm engine on warm weather. When that happened I'd open the throttle wide (only once with out getting the carburettor to pump even more fuel in) and keep it open for 5-10 seconds while cranking the starter. Then, once the engine starts, immediately let go of the throttle before the engine over revs.

Try that out - crank the engine with the throttle wide open for 5-10 sec, see if that gets your engine running. When it starts, check the color of the exhaust fumes - dark black fumes are the result of reach fuel mixture.
 

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Sounds like vapor lock to me. Is there an in-line fuel filter installed? Their extra surface area allows too much heat absorption and they can cause vapor lock. Took me a year to figure it out on mine. Removed the filter and it never happened again. My GL has a strainer on the petcock intake and another in the petcock bowl. It seemed like three filters was just one too many.
Capt Frank
 

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Not sure how to interpret....do you mean engine cranks but wont start...or it does not turn over at all?
 

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Discussion Starter #10
Not sure how to interpret....do you mean engine cranks but wont start...or it does not turn over at all?
Starter turns the engine, there is no any sound of fuel burning in cylinders. Starter turns engine while battery is flat. It is not starting.
 

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Discussion Starter #11
Sounds like vapor lock to me. Is there an in-line fuel filter installed? Their extra surface area allows too much heat absorption and they can cause vapor lock. Took me a year to figure it out on mine. Removed the filter and it never happened again. My GL has a strainer on the petcock intake and another in the petcock bowl. It seemed like three filters was just one too many.
Capt Frank
Yes, I had the inline filter. It was my first idea. There was a bubble in it. But, I removed, the filter. The same situation. It is not helping.
 

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Have you tried a hot start with the throttle wide open? In addition, at the same time have the fuel petcock in the closed position. Both of these suggestions are useful if the no start condition is due to too much fuel.
 

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Discussion Starter #13
Have you tried a hot start with the throttle wide open? In addition, at the same time have the fuel petcock in the closed position. Both of these suggestions are useful if the no start condition is due to too much fuel.
Yes I tried throttle open. I didn't close the fuel petcock still. There is no smell of gasoline and there is no over flooding the carb, nothing comes out of the carb over flood drain tubes.

Anyway I cannot see any other option as to reassemble and clean carbs. It is a little bit painful because I have to order carb repair set, wait for it etc. It takes quite a lot of time.
 

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mine just started doing the same thing. The weather has been really hot. I suspect vapor lock. I balanced the carbs, no help. Mine will start after a couple of minutes. I thing we are getting fuel. Choke does not work either, too much fuel.

I had a 1969 Ford dragster they had a fuel line running to close to the manifold. Once hot that damn thing would vapor lock at any thing under 20 miles an hour. Pulled the line off the manifold and some insulation and never locked again.
 
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