if anyone can help me solve this problem, they are mechanical genius!!

i first had symptoms of a sputtering engine for my 94 ex500 with no throttle response on the highway...after 6k rpm.
next symptoms happened after riding in the city at lower speeds...bike just sputters and dies and can't really start up again.

[ul][*]headlight is fine...battery/alternator seems to be OK[*]bike runs fine when it does run...which indicates carbs are not clogged[*]bike needs to be ridden for some time to show sputter symptoms[*]bike will start with no problems after sitting overnight[*]replaced spark plugs....did nothing. tested for spark on the rubber plugs, spark produced[*]bike runs on one cylinder before dying[/ul]

 

Fuel filter? or fuel line.

 

Runs on one cylinder before dying?

I just fixed a Honda that had the same problem of getting no spark from one coil. Turned out to be a faulty ignition pulse generator (pickup-coil). But on the ex500, I believe there is only one pickup-coil sensor that runs to the ignitor box telling the two ignition coils when to spark. If so, neither cylinder would have spark if the pickup-coil quit working. So, may the ignitor box is at fault.

 

There are two ignition coils. I will test them out. Any other causes?

 

It sounds like there is a plugged fuel cap vent. open cap when bike shuts off to see if there is a vaccum built up.

 

I'm not talking about the ignition coils that generate spark. I am referring to the pickup coil probably under your right side engine cover (not the clutch cover), or under the flywheel cover.

But do test your ignition coils for resistance too right after the problem starts.

 

Or just run with the cap not fully sealed. I like this theory ^

 

edit: duplicate

 

Ignition coils gave me similar problems. After it warms up and dies, pull the spark plugs and see if they are firing when you try to start it.

 

how cleen are the carbs? aer the jets partialy pluged? any sedament in the tank or the carb boles? are you in a part of the country the sells by law a 10% ethonal mix in the fules?