250r runs for 10secs dies

[fatbacktim82]

A guy I work with has an 81 250r that will run for aprrox 10 seconds and then die. It has a new plug, CDI box, and coil. He has tried a different stator too. It isnt a fuel issue that much is known any help much appreciated.

[CodyRx7]

check for a bent float lever in the carb.

[fatbacktim82]

He told me that he took the carb off took it all apart cleanded and made sure everything was correct. I am pretty sure that it is an electrical/spark issue. We work at a car dealership so we decided to go and pick it up at luch and put it in his bay at work, he says its not leaving to it runs.

[Dammit!]

It sure sounds like a fuel issue. That's about how long it will take to empty the float bowl.

There's alot of guys on here that have had all kinds of weird electrical problems but every one I've ever had was pretty simple. It either had spark or it didn't. Nothing that would let it run for ten seconds then quit.

[fatbacktim82]

the reason im saying its not a fuel issue is that we took he tank off and ran it on fuel from a spray bottle it ran no different thna it did with the tank on, neither one of us has ever had on before recently my runs fine but his has this issue. I know the carb is clean and no jets are plugged floats are set right. But we are tired of banging our heads on this.

[fatbacktim82]

Heres an update, we are 100% sure there is no fuel issue the easiest way to explain what is happening is this somewhere in the ignition circuit it is breaking down. it has good spark when we check but dont know if the spark is breaking down under compression or not.

[bigredhead]

compression would have nothing to do with spark ....

and 10 seconds is not long enough for the motor to even get hot.

Have you checked the choke ? is it stuck closed or something like that ?

Maybe try pull-starting it.. might need a jump start !! LOL..

[fatbacktim82]

so fuel under high pressure ie compression, it doenst require higher voltage to create a spark? if not why does firing voltage go up when its under a load? thats why engines miss when under a load more than at idle.

[fatbacktim82]

cant pull start it the clutch cable is broke

[bigredhead]

Compression is the ratio of volume of air at bottom piston position to TDC ,an engine under load still produces the same compression as at idle.. ( Yes.. there are variables here.. as a slow moving piston could loose a bit of air from the ring gaps / valves / etc.... where a faster moving piston will alow less time for this to happen.. but it's negligable i would think )

The voltage is produced by a coil and totating magnets... a full revolution of the crank produces x amount of volts that in turn create a spark when discharged across a plug's gap. Still nothing to do with load.

[bigredhead]

oh.. and no sense in working on getting the engine started if you don't have a clutch cable... gotta fix that puppy first man ! LOL...

[lisnup65]

It still sounds like a fuel issue to me!

But other things to look at:
How is the silencer and the rest of the exhaust?
A plugged silencer will cause the same issue. The engine will start and run for x# of seconds before suffocating itself out. Anyone that use a silencer plug and forgot to pull it can tell you that.

A muti-meter connected to the coild will let you know if signal for spark is happening. I really am doubting that this is the issue as I have not seen it ever before. It should work, or not work!

You say no fuel problems, so I will not go into that. What I would like to know is, does the plug appear wet after it dies?

[fatbacktim82]

plug will get wet sometimes other times its dry hes tried 2 other known good coils and cdi boxes too.