problems w/ '01 yz426f :(

so a while back i was pulling away from a stop and my bike threw a valve. head broke off into the chamber and made a mess. replaced the valve and repaired the slight damage to the piston (header was hardly even marked) and threw it all back together.

now, ive been haveing a mess of trouble getting the bike to run decent. the acceleration is garbage, top speed is half, full throttle it sputters, weak power from a stand still.

ive been playing around with the carb, origionaly the jet was set to 5 and it runs better when i put it on 3. spark plug was showing signs of a rich mix. finally got the pilot set so that the lower rpm responce is better, but i still dont have the power and acceleration that i had before.

is this a carburator problem? or do i need to tear the engine back apart and have another look at all the workings on the top end?

when i rebuilt it, i used the yamaha factory manual, to the "T". i dont doubt my work, and im certain the clearances are to the book. im just stumped now, kinda tired of tearing the carb apart 3 times a day on a hot engine

If you've had the carb apart, double check that the vacuum plate on the engine side of the slide is not upside down. The round side goes up, square side down.

i havent completely disassembled the carb, just enough to access the jet needle. i have yet to check all of the vacuum hoses, but im sure they are clear.

ive fallowed the book pretty much word for word and from closed to 1/4 throttle it runs smooth and just fine. the pick up and power stops there though. probably from about 1/2 to full throttle the bike just makes more noise, no acceleration.

could it be a clutch issue? the bike has a Rekluse z-start with the perch adjuster that i had to disconnect to access the header. ive since left it disconnected.

Clean your air filter lately?

when i had it all appart i cleaned out the filter. ill try running it without the filter, just remove it all together. it doesnt sound like it has breathing problems, but then again i also have a DR.D exaust on it, lol

ok, new development maybe. i think the z-start is screwing everything up. i dont recall the possition of the cables before i disconnected all ot it, and since then i have played around with different possitions with different results. i have the perch, but what i really need is a picture frome someone who has a good working bike with the z-start installed and a pic of the right side where the cluch cable connects to the trans.

anyone out there have a 426 with a z-start???

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