Jetting Questions

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?



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.

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.

Thanks William.

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


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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