For all who deal with jetting...

2 replies to this topic
  • kizzle426

Posted April 19, 2005 - 11:07 AM


I got out to the track on Sunday...all fired up to race...then my bike doesn't start. I was so pissed. It started perfect a few days prior. When we did get it running it kept gunkin the plugs. We took it home ('02 yz426)and started fooling with the carbeurator. We moved the clip up one groove on the needle. Then I turned the pilot screw about 2 1/8 turns out from closed. We tested it out and it started and ran great...there were a few pops on decelleration at first but those stopped after it was good and warm. I'm writing(typing) this just to see if this worked for anyone else. Also I'm wondering if going up one groove on the needle from stock will make it too lean. just let me know. I know jetting changes with temperature and humidity so it might only be something I can know. Also, what are some long term bad effects of running to lean. let me know guys, but like I said it seems to be running better than it has yet. Thanks in advance for all your replies.

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

Posted April 19, 2005 - 12:11 PM


If I'm not mistaken, running too lean will caue your engine to run too hot which then may cause premature wear. I don't think only moving the clip up one position could cause a dramatic problem... specially if the bike ran too rich before.

Again, I'm not the guru here but if I'm not mistaken, the fuel goes though the main jet before going through the needle jet. The way I see it, bigger main with needle down(clip up) or smaller main with needle up (clip down) are approximately equivalent when at mid throttle... I mean, it's not just the needle..

If the bike runs better, can't be bad...

Now let's hear the gurus :naughty:

  • Ga426owner

Posted April 19, 2005 - 12:35 PM


If it is "gunkin the plugs" I assume it is running too rich....... :naughty:

Related Content


yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  35 replies

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.