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Hi guys i have a 1980 yamaha et 250 fires up runs great but after a hour it wont rev enough to engage clutch but idles fine , if i hold throttle open it will die out ..if i let it cool down runs good again .than repeats ..always idles fine tho.. where should i start ? thanks
 

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Hi guys i have a 1980 yamaha et 250 fires up runs great but after a hour it wont rev enough to engage clutch but idles fine , if i hold throttle open it will die out ..if i let it cool down runs good again .than repeats ..always idles fine tho.. where should i start ? thanks
Hi Qtee,

I had simillar issues with my sled. It turned out to be 3 things, look to see if there is a craked or loose intake mainifold coupler. these sleds have problems with the intake coupler cracking and leaking air at the intake, The second thing i found was that the compression was low mine was around 69psi. should be at least 95-100 psi after replacing the rings on mine i was getting 125 psi. There is also a compression realease that could be leaking, and the 3d thing i found was the main seals were fine untill it got up to temp then they started leaking. This is pretty common on an older 2 cycle engine. They will run great cold, But once up to operating temp they start to loose vaccume starving the engine from fuel. Do a leakdown test and that will tell you just whats going on. an check for cracks in the manifold.

hope this helps!!
thanks,
Bry
 
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