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usaf_yz426

yz426 problems

6 posts in this topic

i have a 2000 yz426 with the 450 hot cams installed. i was riding it around last saturday and it was running like a champ, no bogging and started right up on the first kick. so i was on the way back to the truck to put more gas in it, it had about half a gallon left in the tank, when it suddenly started to sputter and then died and locked up. so i put it gear and rocked it back and forth, loosened it up and now the thing wont start.

i have checked and changed these items:

replaced spark plug and there is a white ish blue spark

valve clearence is good

timing is dead on

cleaned out the carb, it was pretty dirty and verified it has fuel flow

air filter is clean

the fuel vent cap works and there is good fuel flow coming from the tank to the carb

i have been trying to figure out what the problem is, i can kick the shit out of it, and it may start once or twice that night, but only run for a split second then it dies.any help would be appreciated, i don't feel like paying 75 bux an hour for some shop to diagnose it.

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i have a 2000 yz426 with the 450 hot cams installed. i was riding it around last saturday and it was running like a champ, no bogging and started right up on the first kick. so i was on the way back to the truck to put more gas in it, it had about half a gallon left in the tank, when it suddenly started to sputter and then died and locked up. so i put it gear and rocked it back and forth, loosened it up and now the thing wont start.

i have checked and changed these items:

replaced spark plug and there is a white ish blue spark

valve clearence is good

timing is dead on

cleaned out the carb, it was pretty dirty and verified it has fuel flow

air filter is clean

the fuel vent cap works and there is good fuel flow coming from the tank to the carb

i have been trying to figure out what the problem is, i can kick the shit out of it, and it may start once or twice that night, but only run for a split second then it dies.any help would be appreciated, i don't feel like paying 75 bux an hour for some shop to diagnose it.

hmmm...that is a good question. Check the jetting!

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What did your carb cleaning consist of?

I would really take it apart and clean every orifice and jet.... sounds fuel related based on everything you say you have checked...

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Does the hot cams intake have adjustable timing like their 426 cams do? If so, is it possible that the cam gear slipped? Are the lobes pointed in opposite directions with about 105 degree included angle with the motor at TDC? If the cam gear moved, the timing would still look right at the gears, but not at the lobes.

Also, by "locked up", do you mean the motor, or the back wheel? if the motor locked up, you could have stuck the piston, siezed a cam, or other costly stuff. If you have the equipment, you might try to run a leak-down test to be sure you have adequate compression...

Are you by chance stationed at Edwards? If so, I'm in Palmdale...close enough to help...

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yep, i am stationed at edwards. it seems that it has great compression. even though i havent tested it yet.

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