03 WR Jetting question

5 replies to this topic
  • GreenRide

Posted May 21, 2015 - 08:31 AM


Hello all,


I recently bought a 2003 WR 450F and I havent got a chance to ride it a lot I have to fix a few things before I do. I took the carb apart because it was leaking from the fuel screw. I checked the jetting while I have the carb out of the bike. What I found is a little confusing and I would really appreciate help on understanding this. Her are the jets it currently has, MJ150,  PJ45,  LEAK 70,  STARTER JET 65, PILOT AIR JET 70, NEEDLE STOCK 4 POS, FUEL SREW 3.5 OUT.


This setting sound like it probably is to lean right ? Is is normal that the bike runs ok like this ?


I've been searching and reading a lot about this this. The bike runs OK, but idle is not that great and there is a little bog when open throttle quickly. I went and ordered what I though would be a good starting point by the TT database, MJ168, 48 PJ, 40 LEAK and a new adjustable fuel screw. 


The bike has a GYTR exhaust insert ,modified air box, grey wire cut and throttle stop cut. It may have the YZ timing but I'm not certain.


Am I on the right track ? please any help would be very appreciated, 

  • Krannie McKranface

Posted May 21, 2015 - 11:12 AM




55 leak

stock pilot air jet

stock power jet

NCVS needle (or JD Red) on 4th clip

Air box snorkle removed

Pea shooter exhaust baffle removed

Replace fuel screw with R&D and adjust for highest idle

Quick throttle requires a linkage spring upgrade, or oring mod (Tokyo mods spring)

Really good throttle response requires a apump system upgrade (crf's only 2008 kit)

  • GreenRide

Posted May 27, 2015 - 08:56 AM


Ok, I got the bike back together and now it run awesome. I think the new fuel screw/pilot and raising the needle fixed my idle and small throttle opening problem. The bike was running good a wot but now it pulls  more and picks the front wheel up in fourth gear just by rolling on the gas :) . The SCAR adjustable with secondary o-ring fuel screw is a must have. Now I can cruise at any speed on the road and have no missing at 1\8 to 1\4 throttle opening. 


WR450F 2003

WR Timing




Stock air jet

Stock Power jet

Stock needle set @ clip pos 5

Air box removed

GYTR Baffle

SCAR adjustable fuel screw

Satisfied 9/10 

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

Posted May 27, 2015 - 09:05 AM


I'll have to tear mine down and get all the right parts, it's good in most placed but bogs if I open the throttle too quickly. Where would you suggest buying jets/needle/oring?

  • GreenRide

Posted May 27, 2015 - 05:37 PM


I live on the east coast canada, so I found i was better off buying my stuff at my local yamaha dealer. I wish I could buy on the nice american web site like RockyMountain and benefit from the nice deals and free shipping. I did order from them before and I got everything right and fast but I got raped on money exchange and shipping.

  • grayracer513

Posted May 28, 2015 - 02:53 PM


I'm curious; what exactly is it that you are referring to as the "power jet" inasmuch as Yamaha makes no mention of it?


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.