00 yz426 starting poorly


9 replies to this topic
  • yama02yz250f

Posted August 09, 2007 - 09:26 PM

#1

I moved up to the big yz426 and my dad is now riding my old 250f. While riding on Sunday it would not start real well. It would take about 5 kicks on average to get it going and seemd to be real hard to kick over, although I think its just becasue im not used to starting the bigger bore. Just to make sure, is it timed right with the 03 450 cam?

Posted Image


I checked the valves and the intakes are within specs but the exhaust clearences are at .356(could barely squeeze them in) So i now I need to adjust those.

I pulled the plug and it was all black so I am thinking that it may be my jetting. Im I right in thinking this? I know nothing about jetting so if that is correct I need to begin using the search feature to learn how to fix it and whether I am too lean or rich.

Thanks

  • grayracer513

Posted August 09, 2007 - 10:21 PM

#2

That is timed correctly if the cam is an OEM YZ450 cam, or an aftermarket cam made for a 450.

If the plug is black and sooty, it can either indicate rich mixture or poor ignition strength. You might want to see it starts easier with the throttle very slightly opened off idle, or with the idle speed raised a little. If it does, try turning the fuel screw in a half turn, or a leaner pilot.

  • USED YZ426F

Posted August 10, 2007 - 05:40 AM

#3

Were you having trouble starting it cold or hot or both?
A sooty black plug usually indicates that the engine is running rich. Do you know if the jetting is factory or not? Where in Washington are you riding? If at high elevations, you may want to lean the jetting out a bit.

  • yama02yz250f

Posted August 10, 2007 - 06:41 AM

#4

It was just starting bad in general, but I was more frustrated with it starting warm...as I expect it to take a kick or two. I do not know the jetting specs because it was bought used. I am afjusting the valves today and am also going to buy an adjustable fuel screw so it is easier to tinker with it. Out of curiosity, how does one fix poor ignition strength?

  • grayracer513

Posted August 10, 2007 - 07:09 AM

#5

It will start better once you get the bike correctly tuned, and also figure out exactly what it wants done. The thing is that they will normally start the same way every time, so once you get the routine dialed, you'll have no trouble.

Weak ignition, if you have it, is corrected by isolating the faulty component and replacing it. The most likely culprits would be the stator (low output) or the coil.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • yama02yz250f

Posted August 10, 2007 - 08:38 PM

#6

I bought an adjustable fuel screw so I will play around with it a bit. Will that help with starting or just the way the bike runs? Which way do I turn it for leaner or richer?

  • ninthrazor

Posted November 15, 2007 - 05:51 PM

#7

Its an '01 with starting issues? I have a 2000 426 and it starts every time with (at most) 2 kicks, hot or cold....usually one kick when hot. If you are having issues starting it, just rebuild the motor, top to bottom. i know that sounds asinine, but think about. You will have a new motor, you will know all the maintenance issues of it from that point on, there is something to be said about a person willing to put the wrench time in: they like to ride with no mechanical issues :-)

  • heineken4menotu

Posted November 15, 2007 - 06:50 PM

#8

THER IS NO REASON TO REBUILD THE WHOLE MOTOR THAT WILL COST AN ARM AND A LEG.:thumbsup: :busted: :ride: TAKE YOUR CARB APART AND CLEAN IT OUT IT HAS SOMETHING TO DO WITH THE ACCELRATOR PUMP:thumbsup:

  • grayracer513

Posted November 15, 2007 - 08:37 PM

#9

Its an '01 with starting issues? ... just rebuild the motor, top to bottom. i know that sounds asinine,

You're right. It does sound asinine.

  • grayracer513

Posted November 15, 2007 - 09:03 PM

#10

THER IS NO REASON TO REBUILD THE WHOLE MOTOR THAT WILL COST AN ARM AND A LEG.:thumbsup: :busted: :ride: TAKE YOUR CARB APART AND CLEAN IT OUT IT HAS SOMETHING TO DO WITH THE ACCELRATOR PUMP:thumbsup:

Calm down, turn the caps lock off, take a breath, use a little punctuation.

It has nothing to do with the accelerator pump.

The usual cause is the idle circuit is set wrong, or, the pilot jet is the wrong size, or it's clogged. Since the bike has been run more or less continuously, and hasn't been sitting, it's probably not clogged, although it could be. Since it used to run OK just a little while ago, the jetting is probably not far off. So, that leaves the fuel screw adjustment. Follow the procedure in this link:

http://www.thumperfa.../jetting.htm#PJ

In for lean, out for rich.

There is one other possibility: rider error.

Watch:

http://www.yamaha-mo...troke_vid_a.mpg

http://www.yamaha-mo...troke_vid_b.mpg





Related Content

Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

First Hare scramble tips by dhend8


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.