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


2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Is the 2016 GYTR Yamaha YZ450F too fast? by Fryboy

Dirt Bike   Special Interest Forums   Pro Racing
  • * - - - -
  • Hot  241 replies

Need help by Goforaride

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  68 replies

Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 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

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.