New 426 owner with ?'s

6 replies to this topic
  • yzfman1

Posted March 10, 2001 - 09:05 PM


Ok, here goes... I'm a new 426 owner in Colorado. This is my first 4-popper so please bear with me. When riding the bike on smooth terrain at a steady throttle, usually between 1/8 to 1/4 and sometimes up to half ( please remember a steady position at one of these intervals) the bike seems to run really rough. The dealer said it was jetted for our altitude (5,000-6,000). When riding normally ie; jumping, play riding, the bike runs fine. I've run about two tanks of gas through it and nothing has changed. I haven't checked what my jetting is yet, so I'm just wondering if anybody knows some baseline settings for my area. I figure if I can clean this up, the bikes gotta run at least a little better everywhere else, right? By the way it has a GYT-R silencer, dealer and instructions said it would make no difference on the jetting. I love this bike(first bike in 5 years) so any help on making it run better if not perfect would be greatly appreciated... Thanx

  • Boit

Posted March 10, 2001 - 11:37 PM


This may be a matter of adjusting the fuel(pilot) screw. Since the pilot circuit affects how the engine runs at low throttle settings, this is a good starting point. Try warming your engine up well with at least 15 minutes of riding and then adjust this screw to give you the smoothest fast idle. Look for recent posts how to do this. Hope this helps.

  • waflnutz

Posted March 24, 2001 - 10:14 PM



when you get an answer, i am seeking it as well. please email

i just purchased a '01 and am conscious of the need to have altitude adjustments made.

word has it vickery yamaha is great at a cost.

where do you ride? i ride in rampart range, berthoud and erie mostly.

email me if you wanna ride some time.


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  • eBayThumper

Posted March 24, 2001 - 10:38 PM


I just brought my new yzr home and it started up fine...then I tried to start it again and realized why I had heard these were hard to start. I'm sorry I didn't read some of these messages BEFORE I had the problem. I guess I 'blipped' it about 2-3 times, which as I hear is about 2-3 too many...hope it goes better in the morning when I promise I will NOT touch the throttle...

  • Taffy

Posted March 24, 2001 - 11:03 PM


try turning the pilot screw out 1/2 turn. however i think that you need a No 125 Pilot Air Jet. this would replace your No 100 PAJ.

this is what i did to mine when it used to vibrate at a constant 1/4 throttle.

i used to open the throttle hard but only after i'd started to roll it first. it was a kind of protection mechanism to stop the engine from spluttering.

now i just lean forward, brace myself & whack it. the difference is huge.

the WR side are already doing this to their bikes. unfortunately the boys are a bit slower over this side.

i think the real difference is that the WR blokes use all the power!



Posted March 25, 2001 - 07:23 AM


I bought my 01 426 from Vickery. I have not had any problems, it runs great. It also has gotten much easier to start with more time on the engine. If you can't get it running right they should be able to. I love this bike (first bike in 15 years after ruptured acl & mcl).It's everything I wanted my 85 KX 500 to be.

  • Boit

Posted March 26, 2001 - 01:12 AM


Codswallop! You always need a starting point. Some call it an index.

Mad Potter: Not meant for you.

[This message has been edited by Boit (edited 03-26-2001).]

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