YZ 426 start problems

7 replies to this topic
  • yamaha_mx_13

Posted June 29, 2008 - 12:59 PM


My Yamaha YZ426F is extermely hard to start. Every once in a while i'll get it started, but thats it. Ive tried all the methods on thumper talk but they dont work. Can anyone help me.

  • YamahaYZ426F

Posted June 29, 2008 - 01:56 PM


Have you checked if the spark plug is fouled becuase alot of people foul the plugs becuase when starting the bike they twist the throttle which fouls the plug eventually.

  • ricky_arthur

Posted June 29, 2008 - 03:03 PM


+1 the only time my 426 needed more than a kick or two was before I retted it and had fouled a plug. since then the hardest time I have had starting it was yesturday after laying it over on a hill climb, took 4 kicks because I didn't use the hot start on the first 2 and because on the rakish angle I couldn't get a solid kick. My 426 at least, is not hard to start provided I use choke when cold, no choke if it's even warm outside, and hot start if I have killed it while riding. if I simply shut it off like say to rest for a sec or talk, it will start with with no hot start.

The usual routine for hard to start is check plug, air filter, check Jetting, check valves. If it's not starting easily you are doing something wrong ie. hitting the throttle while kicking or something is mechanicaly wrong.


  • laserracer

Posted June 29, 2008 - 04:00 PM


hi mine starts best by giving it 2 slow kicks on the kickstart twist the throttle once then release it, then kick it and it will start, cold i use the choke hot its the same as ricky_arthur maybe check your valves are at the right settings p.s mine has the 03 450 cam in it so has no decomp lever

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  • yamaha_mx_13

Posted June 30, 2008 - 09:30 AM


I checked the spark plug, it is fine. But my valves are in need of a replacement. I dont know where to get valves though

  • YamahaYZ426F

Posted June 30, 2008 - 10:26 AM


If you want oem valves thumper store is the best place to go or bikebandit if you want to go with aftermaket valves



hope this helped good luck :thumbsup:

  • shrekka

Posted July 05, 2008 - 04:01 AM


check your flywheel from crud buildup, like mine was
would start then run like a pig, the wouldnt start at all...

found my flywheel the cause, now starts 1st kick

  • 1rkcooper

Posted July 05, 2008 - 06:03 PM


I checked the spark plug, it is fine. But my valves are in need of a replacement. I dont know where to get valves though

So what leads you to believe that the valves need replacing and not just an adjustment made on the shims?

If you haven't already, you should put a new plug in it. If you go to the YZ forum and into the common threads sticky, at the bottom of the page there are two videos from Yamaha on starting procedures, watch these videos to be sure you are using the right technique. If none of this works you should check the valve clearance and adjust if needed.

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