Question about 2003 Yamaha YZ 250

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My 04 blaster smokes and idles poorly,dies pushing throttle

I recently bought a 2004 yamaha blaster with the oil pump removed so you have to mix your own oil.I am mixing the oil exactly at 32-1 with yamalube 2 cycle 2r oil and 93 octane fuel.This thing smokes badly9( White smoke) and oil drools from the exhaust outlet of the engine where the exhaust bolts on.I have completly rebuilt the carb,rejetted and set float level all to factory specs.I changed the clutch oil and now when i hit the acclerator the the thing boggs down and dies.But even at idle,it idles differently than before i changed the clutch oil.Spark seems good.Reeds look ok.used but not damaged.Plug looks new but gets oily.Bad clutch side crank seal?Crank seal looks good visually. I pulled the cylinder head.rings ,piston etc. looks good and new.This thing supposedly had a top end rebuild nov 08 just before winter.I bought it the end of april and have not been able to ride.
Any suggestions?

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  • kwbuccaneer May 28, 2009

    I figured it out after I opened the crankcase suspecting cranshaft seal failure.Crankseals were not leaking but same symptoms.Crankcase had cracks from bits of leftover metal falling into the bottom end when the top end blew,then was replaced.If you are having these symptoms:Oil drooling from exhaust,white smoke from exhaust(right sidecrank shaft oil seal=sucking in gear oil),idle hanging up high after reving(left side crankshaft seal=sucking in unmetered air),

    then your crankseals are leaking or your crankcase is internally cracked.

    Either case,the crankcase needs to be split open and rebuilt.




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Stock pump sucks. i run 32:1 in my bike and runs great. take it to a dealer and have them check it out

Posted on Feb 14, 2010

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Hi I am vortash .. firstly 32 - to - 1 may be a tad high I would say ... it would be fine at the same as the ducati ratio 20-to -1 with a good quality oil , you should check that your sump is not filling with oil as this will cause performance problems with backpressure .. but maybe the best thing to do would be to replace the oil pump and run it as it was designed to do ?. I am sure you will get one off the net cheaply or from a local bike breakers .... Regards Vortash

Posted on May 18, 2009


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