08 450F - Big Bore Jetting & other questions

1 reply to this topic
  • NewMexican

Posted July 25, 2011 - 04:22 PM


Ok, so I just put in the Cylinderworks 480 kit (with +3mm Vertex piston).

Seemed to be running very lean, so I've re-jetting a few times already.

Now I'm at 5000ft high desert, 90 deg, 48p, 175m and the Half-step richer needle in stock clip position and 2 turn out on Fuel screw, O-ring trick in place, and everything else is stock.

Seems about 95% good now, seems to have either a cough, bog, or surge at 1/8th to 3/8th throttle. I can't really tell which, but something wierd happens around there every now and again.

So anyhow, do you usually have to go so big on the jetting with a big bore on these bikes?

Any other tips or tricks when going the big bore route on 4-strokes? I'm considering bigger and stroker next time as well. I can see a bit more power that I like so far!

Thanks in advance for your comments!


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

Posted August 01, 2011 - 04:32 PM


I'm still at 48p, 175m but I put the stock needle and dropped the clip 1 position (richer) and down to 1.5 turn out on Fuel screw.

Seems much better, it had some hesitation or blubber at 1/8 to 3/8.

It did cough once on my last ride around that area of throttle, and only after either:

1) Chopping the throttle off on (due to corner or whatever obstacle coming)
2) Hitting a section of whoops then chopping the throttle on - off again

Other ideas?

It's actually really good now, and I'm calling this my YZF 505 (since it's really the same size engine as the KTM 505)! :smirk:

Related Content


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
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • - - - - -
  • 0 reviews

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 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.