New 2003 WR450 - Thanks to TT - A Few More questions

I purchased a new 2003 WR450 about a month ago. I was somewhat disappointed in the performance of it. In the last month I have read up on the bike here on TT and here is an update.

Here are the updates I have made.

1) Took out exhaust plug and replaced it with the GYT-R end.

2) Took out air box restricter.

3) Replaced throttle stop with one from YZ.

4) Rejetted to 165 MJ - Moved clip to 5 Pos. - Idle mixture screw 3.25 turns out.

5) Disconnected gray wire.

6) Installed Acerbis hand guards.

7) Got inspected by police so I can get plates.

WOW - A very big improvement, the bike really revs out now, much better power across the board. Can't wait to take it out in the woods and really test it.

Here is what I plan to do next.

1) Do the starter mods - I just got the rest of the parts to upgrade to the 04 setup.

2) Hook up the brake light. I have hyd brake switch for rear.

3) Get a bracket for license plate from 4 strokes only. Put on plates.

4) Re-route vent hose(s) to air box.

Follow - up questions.

1) What is the easiest way to hook up brake light to utilize what wires / etc are already there?

2) What do you about the jetting I have done? Any further suggestions?

3) Any other things to do to the bike?

Thanks so much, this forum has helped me so much.


>Took out exhaust plug and replaced it with the GYT-R end.

Dan, if you put a real open exhaust like the yz the different will be amaizing!

> Idle mixture screw 3.25 turns out.

NEVER run screw out more than 2 turns out as you re going to loose it. If 2 turns are not enough you must go to the next larger size.

About rerouting breather to the airbox - there is a place that yamaha design it to go - on the top of the rubber boot. You must open/punch the hole.


hoghead450 the mods are never ending,its part of the fun. Sounds like you have it covered though. Now ride that thing. :thumbsup:

i'm not sure i would cut a hole in the air intake boot for the reroute. go to and find the wr450 project bike. they have photo's of the reroute. or you can put a tee fitting in the hose and run a short length up behind the radiator. that will also prevent the hose from sucking water if you stall and restart in a creek.

on the sides of the carb there are small tee fittings with vent hoses. the two hoses (one from each side) that run over the top of the carb are long enough to run up along the frame towards the air box intake area. this will allow two vent hoses to stay out of the water when crossing creeks. having all the vent hoses in the water can cause the bike to stall in longer crossings.

as was said above, don't run the pilot screw out more than a couple turns. they do fall out. you might find the screw(not) but you'll never find the o-ring and washer. go up a size on the pilot jet.

a lot of us have gone to the JD jetting needles. if you don't want to spend the money, try the '04 needle. it's an improvement over the '03. it might not give you the flexability the JD kit does, but it will be better than stock.

good luck

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