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bigthump426

2000 yz426 timing and valve problems?

6 posts in this topic

I can't get my bike running at all if the valve clearences are off will it even try to start and where should my cam marks line up with tdc

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The first thing is the starting technique, but I'm assuming that you've had the bike for a while and know that one. If not, watch:

http://www.yamaha-motor.com/sport/4stroke_vid/4_stroke_vid_a.mpg

http://www.yamaha-motor.com/sport/4stroke_vid/4_stroke_vid_b.mpg

If the valve clearance is too tight, as in from .05mm to less than zero clearance, it can make it nearly impossible to start, but you should notice a lack of compression. Cam timing is in the manual:

http://www.yamahaownershandbook.com.au/?r=0

http://www.yamaha-motor.eu/eu/services/owner-manuals/index.aspx

You may want to download the '01 or '02 manual as well as your own since they started using drawings in '01, rather than photos, and these tend to be much clearer and easier to understand.

Otherwise, the two most common problems with getting a 426 to start are the carb (usually the pilot jet or some other element of the idle circuit) or the spark plug. The ignition at starting speeds is a little weak, and it doesn't take a lot of stuff on the plug to effectively foul it.

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Just cleaned the carb new plug but there is lack of compression I'm able to kick with no help from the decomp intake side is .004 exhaust is .012 the exhaust cam mark sits just below top of the head

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Put the crank on TDC then check the cam marks they should be straight across from each other.

Pull the spark plug out makes much easier to turn the motor over if you have not done this already.

After you get the cam timing right then check the valve clearance.

I read have you past posting if you can chain was that loose you could of jumped a cam tooth what I see looks your off 1 tooth of the cam.

Turn threw motor over by hand after you do any adjustments to the motor to make sure nothing hits like valves to piston.

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