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View Full Version : 07 yfz450, jetting


Danab138
09-29-2008, 05:32 PM
cant figure out how to set the carborator adjestments, cant even get it to start. bike is totally stock except for the a/f screw i replaced. the stock one was snapped off by whoever had it before me. i got a stock size and just cant get it to start. .











also im looking for a clean frame with title. the bike has a cracked frame and id rather replace it than have it fixed.
ohsobad_chevy
09-30-2008, 03:37 PM
Welcome to atvriders. :)

Since you have the aftermarket fuel screw, then you know how to adjust that. The main and pilot jet are accesible on the underside of the carb, there is a 17mm nut that you take off and you will see both of them. The pilot is elongated with a flat head screw driver and the main is shorter hex shaped 6mm. To get to the needle (stock needle is not adjustable, I recommend the NCVQ needle) you will need to remove the plate on the top of the carb, open the throttle to raise the slide and pull the needle out. On the new needle, it will have an e clip where you can raise and lower it. Raising the clip = leaner, lower = richer. ;)
Danab138
09-30-2008, 11:17 PM
yea so the jets were totally clogged! shes spittin fuel beautifully now but that only allowed me to encounter my next problem! carb seems to be AOK but iv determined im getting NO spark at all which explains why it never even made even a pethetic atempt to start! i used a logic probe with the ignition on ovb, coil disconected i probed the input wires to the coil and im getting no pulse width during cranking so that should eliminate the coil and plug from being bad cuz they aren't getting a signal to fire to begine with. . i understand this could posibly be the magneto? ? what i dont understand is how a brand new quad with less than an hour on it and tires that are clearly not even broken in would have a bad ignition system? i already checked the stupid stuff like fuses and what not. . if anyone has an idea or some diag tips i would apreciate it.
ohsobad_chevy
10-01-2008, 05:39 AM
Not even an hour on it..?..? I would be hauling that sucker right back to the dealer. They will fix it.
Danab138
10-01-2008, 03:27 PM
yea but i got it threw a private sale so i was just ganna fix it myself. .