Jetting Questions

4 replies to this topic
  • mweitz

Posted October 06, 2010 - 05:46 PM


Do you keep spare jets in your toolkit?

If so, how often do you need to use them.

Do you keep spares of what you have and some different sizes?

I pulled the carb on the WR tonight, I think I could rejet it in 30 or 40 minutes.

My bike currently has:

170 main
45 pilot

Leo Vince full titanium exhaust

03 YZ450 Cam

YZF450 Quad needle - set in 3rd position

Fuel screw 2 turns out

This is to run at sea level to 2K' or so.

(I bought the bike jetted like this)

If I went to 6K would I need to change the jetting and if so what is a good assortment to have on hand?



  • Flagstaff

Posted October 07, 2010 - 08:07 PM


I don't know, I jetted based on recommedations posted here for 7000', ride 4000' to 10000' , am happy. Guess I'm not as sensative as some folks.

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  • William1

Posted October 07, 2010 - 10:35 PM


I keep a full selection of needles, mains, pilots, leak jets and replacement parts.

Basic rule is if the elevation is more than 2,000', a rejet will make a noticable difference.

If you went to 6k, you would need to lean everything out. Probably at least a size on the pilot, main to 160, needle on the first clip at a minimum.

Fuel screw should be reset for temp/alt/air density change.

  • mweitz

Posted October 08, 2010 - 05:34 AM


Thanks William.

I guess I'll just throw a jet in my regular orders here and there.


  • mweitz

Posted October 13, 2010 - 10:12 AM


Hmmm, before we get too far, can I get some specifics.

This is how my bike is currently setup.

Model: 426
Cam Timing: 2003 YZ 450 CAM
Main jet:170
Pilot Jet:45
Leak Jet:STOCK
Starter Jet:STOCK
Fuel screw (turns out):2
Needle Model/Clip position:3 (Needle from YFZ 450 quad)
Grey Wire Mod (Y/N): Y
TPS Connected (Y/N): Y
Airbox Snorkel/Lid (on or off): OFF
AIS Removed (Y/N):N
Airfilter Brand:?
Exhaust Brand: Leo Vince full system
Average Altitude:Sealevel ( California)
Average Temperature: (60-90)
Average Humidity: 60-70
Degree of Satisfaction (0-10): 8
Additional Mods/Comments:

I would like to sometimes run a stock 01 YZ header and exhaust (I have a new one).

What would be a good place to start on jetting for that?

What would a good few main and pilot jets be to order to have on hand, say I want to order 4 or 5 of each to start with?




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