Anyone have jetting specs for the 08 yz450f???

I was looking for a base to start twaking the jetting on the 08 450f. It backfires and seems to be a little lean and of course is not the easiest thing to start.

I am at 85-90 degrees at 600-800 ft elevation and 70-90% humidity.

South Carolina

Sounds like history is repeating itself....06...07 now the 08

go up 1 size on the pilot jet....and in this heat here in the SE 100degrees + with 80%humidity......good luck finding a good combo.....

adjust the fuel screw - I hope you bought a adj fuel screw....:thumbsup:

I had to go down 1 leaner on my mj on my 06 and up 1 richer on my pj...fuel screw adj in am will be different in the afternoon heat 1.5 - 2.5 range out

wait... the bikes dont come with an adjustable fuel screw? or is the stock one not great? it would be kinda stupid to sell the bike without something it needs to perform properly wouldnt it?

wait... the bikes dont come with an adjustable fuel screw? or is the stock one not great? it would be kinda stupid to sell the bike without something it needs to perform properly wouldnt it?

the stock FCRs on all bikes come with a fuel screw that is recessed into the carb. It can be adjusted by a 1inch screw driver or by removing the carb...either way it is a real pain in the @$$, because there is no good way to tell how much adj is measured.

A adj Fuel screw is longer than the stock recessed screw. The decent ones have numbers on the end to measure exact turns in and out. All FCR equiped bikes need to have the fuel screw adjusted at some point to compensate for temp and humidity changes Richer/leaner conditions.

The Adjust Fuel screws cost about 20.00 and sure makes carb life/tuning easier. Unfortunately they do not come stock, but sure should. :worthy:

yeah, i just found out how much of a pain that is this morning. i found something that works pretty decently until my fuel screw gets here (i ordered a Turner adj fuel screw), i took a 1/4" drive ratchet and put a 1/4" socket on it, took a flat head bit from a multitool i have slid it into the socket and used that. fortunetly it had lettering on one side so i didnt have to make any marks and i read it just fine.

I was looking for a base to start twaking the jetting on the 08 450f. It backfires and seems to be a little lean and of course is not the easiest thing to start.

I am at 85-90 degrees at 600-800 ft elevation and 70-90% humidity.

South Carolina

curious please tell me the stock jetting from the 08 manual....include the needle jet - NF.....part number, clip position mj , pj and lj

thx

curious please tell me the stock jetting from the 08 manual....include the needle jet - NF.....part number, clip position mj , pj and lj

thx

Main jet #160

Pilot Jet #45

Needle Jet NFLR 5TA-14916-LR (Jet Needle Groove #3)

Leak Jet #55

Hope this helps

This is what I have done. I am running stock pipe and silencer so you know.

And you know we ride at the same tracks just not the same speed there DJTROY.

I went up to 165 MJ (tried a 170 too but it got worse so went back to 165)

I went up to 48 PJ

I am between 1 1/2 to 1 3/4 out on fuel screw

Everything was running pretty good with a little hesitation with throttle just barely open. So I raised the needle one spot. It is now pretty good. Just not as crisp as it is 3/4 to full throttle. Next time I have it appart I am going to raise it one more see if it gets better or worse

It still has a pop to it but not a back fire like it did with the stock jets. With the stock jets it was actual fire and loud exposion type back firing. Now it just pops (Way different sound then before way softer and deeper with less of a cracking type sound) Hope that makes sense. From what I have read that should be normal.

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