Carb Jet Question

My bike is an '06 WR450 with a carb (not FI)

There are a couple of jets in this bike that I have never seen before

A starter jet and a leak jet


I'd imagine the starter jet is as its name does this tie in with the choke knob I pull out?


Leak jet ????

The starter jet is the tuing jet for the choke circuit.


The leak jet is not really a jet: it is the 'overflow' of fuel going to the apump system.

To keep more fuel in the apump system, you put in a smalle4r leak jet.

SOP is to go to a 50 leak, a 2008 CRF450R diaphragm and push rod and pump cover, and a Tokyo mods apump linkage spring. Better than FI, then.

a 2008 CRF450R diaphragm and push rod and pump cover,

You mention this quite often, but there is a problem... which of the two part numbers

are you referring to? There are two, and both of them show as used on 2008 CR450F

16021-MEB-771 2003-2008 CR450F

16021-MEN-A01 2003-2013 CR450F

My suspicion is it is the MEN-A01 varient, but if you could confirm that would help all

future folks that would want to try the mod.

Damn,  Ka Ran Nee You know this stuff inside and out!


I have an '06 WR450 that I bought a couple years ago

It ran pretty good so I just left it alone

I have never taken the carb out so I dont even know if I have stock jetting or what

Although I cannot see any trace of the AIS system I am supposed to have

Which would poss indicate that someone has been in there


I am in New England where the temp is 50 - 90F when I ride at 0 -100 ft above sea level at most


I am waiting for our weather to get a bit warmer so my jetting changes will not be thrown off by dry cold winter air


I am very curious to see what is going on inside the carb

If I see all stock jets I think I have a blank canvas to try a bunch of things

If I see non-stock jets, my guess is that somebody has already been through all this,

so If I make any changes, they should probably be small incremental changes


My gut tells me this bike should run alot stronger than it does

It runs nice, dont get me wrong

but I'd expect the front wheel to come up with a twist of the throttle rather easily

right now you have to really work it to do that

I suspect it is running lean all across the board

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