Help! 2006 yz450f big bore problems

1 reply to this topic
  • drave199

Posted January 25, 2014 - 01:28 PM


So im trying to help out my buddy who is having trouble with his 478cc big bore kit. i guess his issues are with tuning it properly. it is back firing and will only idle on choke. 


ill try and get more info but does anyone have any advice as to why this is?? 



Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted January 25, 2014 - 06:19 PM


Sounds like a standard case of the pilot jet being clogged. Happens very easily if the carb sits and dries out for a while, and it may even look open. A dried film only .001" thick will change a #45 jet effectively into a #38, way too small to work. Visit the topic, "Common Threads", and look for "Cleaning Jets and Carb Passages".

Related Content


BIGBORE FOR YZ450F 2006? by Taattie94

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

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

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

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 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.