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Discussion Starter #1
I have a problem with a Suzuki T500 and its running away and can't be switched off! Any ideas? Its not electrical as at low revs the ignition switch works. I am of the opinion that at high RPM the engine starts to "diesel" and Its happened when the choke is left on too long. Its a pretty scary thing as this is a 1971 T500 without a kill switch which would be useless anyway once its making its own fire! Has anyone ever seen this happen before and is it a common problem? My first road bike was a 1969 250 Hustler and it never happened on that bike. Any ideas would be greatly appreciated.

Thanks.:coffeescreen:
 

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Time to take a look at your carb. Is the idle set too high? carbon build up from running rich and low octane gas often contributes to this. Adjust your carb first, then adress the carbon build up. Maybe seafoam.
 

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Discussion Starter #4
Time to take a look at your carb. Is the idle set too high? carbon build up from running rich and low octane gas often contributes to this. Adjust your carb first, then adress the carbon build up. Maybe seafoam.
Thanks ET....I have pulled one carb apart and she's fine. I have also just had it running nicely but if I open it up suspect she may over run again. Thanks again.
 

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If it is only doing it when hot, it due to carbon imo. The carbon comes from running rich. Either the choke stays on or the carbs need to be adjusted leaner. Then seafoam. Pull your plugs to check for rich running.
 

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The 450 Kawasaki dirt bike from the 70s did the same thing. Blocking the intake would stop them.
If it is carbon build up, I suggest you remove the head and clean the combustion chamber, which includes the top of the piston. It could also be running too rich, fuel, or too rich with oil. Or the oil is not of good quality.

However, most engine runaways are due to an air leak on the intake side.

You probably have an oil pump on that model. From memory I think they are adjustable.

Unkle Krusty*
 

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Discussion Starter #9
Yep, that could have something to do with it. The previous owner has put mixed fuel/oil in the tank as the bike had not been run for a while and it has an oil pump running synthetic oil also. Maybe I'll run this tank out or drain it and fill with straight fuel & see how she goes. Thanks again.
 

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Yep, that could have something to do with it. The previous owner has put mixed fuel/oil in the tank as the bike had not been run for a while and it has an oil pump running synthetic oil also. Maybe I'll run this tank out or drain it and fill with straight fuel & see how she goes. Thanks again.
They did not use synthetic oil when the bike was new. I suggest you fill the oil tank with regular two stroke oil, and make sure the oil pump is pumping. I think you can see the oil moving in the plastic tubing, especially if it is a dark colour..

Unkle krusty*
 

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Is there 'Free play' in your throttle cables! If the kill switch or the ignition switch doesn't stop the fun then the engine is 'Dieseling,' from something that is providing a 'Spark.'

Sam:coffeescreen:
 

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Discussion Starter #14
Does anyone think that a two stroke with leaking seals could be the cause of this or is it just more likely to not start if the crank shaft seals are leaking?
 
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