YZ426F help.

25 replies to this topic
  • Mike Taylor

Posted February 17, 2010 - 07:57 PM


I recently bought a 00 YZ426F. It is stock to the best of my knowledge. The problem is it's an absolute bear to start when it is cold. Once its warm or hot it will fire first kick every time. (usually dont even need the hot start) Other than a little bog of the line it runs great. I cleaned the carb and had the valves adjusted. I did the light blue neutral wire mod. I sanded and cleaned the coil mount and contacts and even put in a hotter plug NGK CR7E as a last resort. Still it is a pain to start. It actually seems to try and start better without the choke??? Could this be a jettin issue? I was also going to do the av now or the james now mod. I cant seem to find any instructions on it though. Can anyone help me out with a solution and or the insructions for the mod? thanks in advance..

  • l_campionero

Posted February 17, 2010 - 09:13 PM


Are you strictly following the procedure for starting a bike with a manual compression release? If you deviate in the slightest, they can be a bit difficult to start.
I had a 2000 YZ426F and could start it in houseshoes.

  • myoung

Posted February 17, 2010 - 10:03 PM




There's a hole that gets drilled that isn't in the drawing. The dimensions could be adapted from the pics in the AVnow link.



This is from the inventors website. Thumper Talk member AV

  • DeeCee

Posted February 18, 2010 - 12:43 AM


I agree with 'l_campionero' once you have the technique right, they can be started very easily.

One of the main issues new 'starters' find is they twist the throttle when kicking. This is an absolute no-no (never). The slightest twist and you may add minutes into the time to get it started.

I have generally found once the jetting is close, starting is not the issue. Sounds as though you have your jetting close, so I would focus on starting technique (see the video in the sticky's) for this.

  • rufusz

Posted February 18, 2010 - 02:57 AM


Get an adjustable fuel screw and dial in your pilot circuit. IMO this has the biggest effect on starting, specially cold.

  • grayracer513

Posted February 18, 2010 - 09:07 AM


Rufusz is correct. At least on that part.

426's are extremely sensitive about two things when it comes to starting:
Correct idle mixture, and correct procedure.



I notice you list your location as Pennsylvania. Rumor has it that it's a bit cold there. An extra squirt or two on the accelerator pump may be needed to overcome that.

  • Clint12

Posted February 18, 2010 - 12:04 PM


i have a 2001 YZ426 and i live about 400 miles North of you (Toronto Canada) and yes it can get a little cold here just like PA... my bike is really hard to start in the cold as well other than technique like these other guys said make sure you have fresh fuel in it.. of course buy the highest octane you can for it. If my bikes sits in the cold garage for any more than two weeks without starting I drain the fuel out and put new stuff in. Good look and ummmmmm kick it over like a man

  • grayracer513

Posted February 18, 2010 - 12:23 PM


.. of course buy the highest octane you can for it.

Paying for octane beyond a U.S. anti-knock index of 91, or a Research Octane of 95, is a simple waste of money, and will accomplish nothing beneficial for starting or otherwise.

  • cowboyona426

Posted February 18, 2010 - 12:28 PM


FWIW, the JamesNow type gizmos are just about a complete waste of time and money. If the bike is properly jetted one of those pieces of tin isn't going to make a difference. I had the original built by James JamesNow in my old 00 426 right up until the day my bike started running like crap out of the blue. Pulled the carb out to find the plate had come loose and bent upward in a U shape. Took it off and never looked back.

  • Mike Taylor

Posted February 18, 2010 - 01:57 PM


Thank you all for all the responses. As far as the starting procedures. I have read many on here and used what i think would fit for my situation. The temp here has been in the 30's for weeks. So i have been wicking the throttle 3 to 4 times then kicking the bike till the "hard spot" TDC i believe, then pushing an additional inch to two. Then return the kicker to the top and give it a boot.. If i do this without the choke on it will usually caugh a little so ill set the kicker again and kick it again.It will usually run for about a sec or two. then shut off over and over again. If i pull the choke at this point it won't even try to start? seems like the choke circuit is over fueling it. So i clean it out (pull the comp. release and kick it about 10 times). Then do my procedure till it will run long enough to reach down and get the choke. Then the bike will idle up and run fine. this could take kicking it about 20 times till i get it.

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  • grayracer513

Posted February 18, 2010 - 03:28 PM


Check the size of the starter jet against the manual. Could be oversized.

Also, consider trying with the choke, but with fewer twists of throttle.

  • Mike Taylor

Posted February 18, 2010 - 05:43 PM


ok will do. thanks

  • Clint12

Posted February 19, 2010 - 05:39 AM


did you check your kill switch? i have heard of them faulting out before which could be the problem.. maybe try disconnecting it and give it another try.

  • Mike Taylor

Posted February 19, 2010 - 01:53 PM


disconected the kill switch still hard to start. thanks for the thought.

  • baxterj787

Posted February 19, 2010 - 07:32 PM


I think GreyRacer is close to the mark. I live in Dayton, OH. My drill (with manual decomp or the autodecomp) is choke on, two twists of throttle. Follow the kicking/TDC procedure you described above. One kick will get mine to bark for one to two seconds.

If the weather is cold (30s), I will do the same drill, only one twist of throttle. 9 times out of ten, it will start and run. The tenth time? Well, I like to think of the other nine times...

If the bike is firing and running briefly, try turning up the idle about half a turn. The short run time is the fuel signal from the AP burning off. No ignition troubles.

For specs, my 426 (2001) is stone stock; 42 pilot. Cr8E plug. Stock exhaust, too. No idea where my fuel screw is set. I do know it has zero bog, and that is good enough for me.

  • baxterj787

Posted February 19, 2010 - 07:41 PM


One other thing I forgot: if the small o-ring is gone off of the fuel screw, this will cause starting headaches. Find out where your FS is at present (EX: two turns out from fully closed), then carefully unscrew it and check for the spring (about 17mm long and skinny), then a very small flat washer, then an equally small o-ring. Sometimes the o-ring likes to hide inside the carb body, other times it will come out with the FS assembly.

  • Mike Taylor

Posted February 21, 2010 - 03:17 PM


thanks again man. looks like the "o" ring on the fuel screw is bad. gotta get one and see if it helps.

  • Lota Fun R

Posted February 22, 2010 - 12:53 AM


Mine starts in one or two kicks. It's an 01 with stock jetting and settings. 1&1/2 turn out on the needle screw/idle mixture.

If it's warm you just kick through, no throttle. Just one 1/3 turn throttle, roll over til won't kick, hit release and move through a little and then kick, no throttle....take your hand off of it.

Or use choke but it doesn't usually need it. It's getting enough gas.

  • nathanpa01

Posted February 22, 2010 - 10:23 AM


Hey Mike, where in Pa are ya? I'm just above Reading. Where do you do most of your riding?

  • Mike Taylor

Posted February 22, 2010 - 02:33 PM


live in hanover now. grew up in new holland and morgantown near reading. Ridin in tower city right now.

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