High altitude carb tuning 400f

3 replies to this topic
  • jagarcia89

Posted September 28, 2009 - 04:03 PM


My bike came from sea level so I jetted it to local shops recommendation, it now fires up first kick with a bit of gas but won't idle without the choke on or giving it some gas. I then turned the screw on the bottom out a few turns and it would idle for a little bit longer then die. So I figure I need to richen it up. My question is how many turns is it safe to go out on the adjustment screw because I went 7 before thinking it may be too far. Based on the change going from 3 to 7 turns, it seems I'd need like 10-12 turns. Given that I'm fairly confident that's too much, how much should I increase my jet size so I don't have that thing holdin on by a thread? And lastly where can I find a heatshield for this header??

  • grayracer513

Posted September 28, 2009 - 04:15 PM


What is your altitude?

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jagarcia89

Posted September 28, 2009 - 06:37 PM


Most riding is done at around 6000ft right now but would like to hit a few local trails that get to around 7000 if possible

  • grayracer513

Posted September 28, 2009 - 10:17 PM


Multiply the sea level jet sizes for the main and pilot by 0.94 and start with that.

Related Content


2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

First Hare scramble tips by dhend8

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

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

The "going back to the other darkside" adventure... by Monk

Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  94 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.