New Pipe Jetting at Sea level

3 replies to this topic
  • YZThump

Posted July 02, 2001 - 11:28 AM


I just installed a DSP Titanium pipe with a Spark Arestor. I went up one on the Pilot and Main jet and it has a little hicup now at first blip of the throttle. Other than that evrything is great,even seems quieter than stock.

  • Boit

Posted July 02, 2001 - 07:35 PM


I found the exact opposite helped me turn my 426 into a raging beast. I'd suggest make one change at a time and test. Start with one leaner on the main and test. The thing I noticed about this machine is to change a jet and ride at least a half hour before making a decision to move to the next jet size. The bike seems to need a little running time to adjust to the new jet size. It probably has more to do with the spark plug having this new mixture thrown at it. Take your time.

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

Posted July 03, 2001 - 12:36 PM


So your saying I'm going richer when I should be leaning it out? It feels like it is rich,how is yours jetted Boit?Do you have an after market pipe? The Beast part is what I'm after.Have you done the throttle mod that was talked about by Ferry's mechanic?Thanks in Advance!!!Any help would be appreciated,1st thumper.

  • Boit

Posted July 03, 2001 - 04:05 PM


I have a '00 426 and had that annoying hesitation when I would try and whck the throttle open suddenly. Installing the P-38 plate(which does what the Ferry mod is meant to do), using C-12 fuel and careful jetting solved ALL my problems. I'm using the White Brothers "E" series carbon fiber silencer with the titanium hi-boy head pipe. This combination gave an incredible boost right off idle which is what I wanted. As summer has arrived, I'm at a #158 main jet with everything else stock. During the winter, below 50 degrees F, I used a #160 main jet. It's pretty amazing when you get the correct jetting. It's like the engine gets a new life. Cold air is dense so to compensate, slightly richer jetting is needed. The opposite is true for wamr/hot air. One thing that has become apparent is that there seems to be a difference with each and every 426. Your bike could be set up identically to mine and yours might run better on slightly different jetting. If you are willing to try different jetting, the rewards can be significant. Hope this helps.

[This message has been edited by Boit (edited 07-03-2001).]

Related Content


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

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

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

05 yz450f not fast enough by RedeyeYZ

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 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.