New 05WR450F, What Mods, What's Air Induction, and Descrepancies

19 replies to this topic
  • jdd123

Posted December 27, 2004 - 08:02 PM


Just traded in my son's bike and my YZcam/free mods 03WR250 for an 05 WR450. Son ran away to birth parent, different story. Anyway, what is this air induction system and what mods apply? Yamaha has done a number of nasty things to stop one from doing any performance mods. What's up with that? Here are the problems I discovered so far.

The exhaust is internally restricted. Do what you want with the tip, it doesn't matter. There is a 1" hole going into the spark arrestor chamber. If you want airflow, get a new muffler.

There is no fuel screw and the jetting section is ommitted from the manual. I tried to install a zipty screw and found a plug on the carb bowl. I checked the manual and cannot find the fuel screw in the parts breakout or the carb assembly section. I will remove the bowl tommorrow to verify this. How can you FINE tune/adjust the jetting up to 1/4 throttle? Does Yamaha expect us not to jet or does this new air injection system help with the mixture.

What does this new air induction system do? It goes from the air box to the exhaust and also just after the carb. I thought it was just to dulute the exhaust for CA emissions green sticker. Thanks CA, our air is to thin in CO and we need all the airflow we can get. Could this somehow mechanically adjust jetting by adding air to the mixture after the carb? It is only mechanical not electronic.

Does the grey wire mod apply? There seems to be a rev limitation even when in 5th gear wide open.

Wich brings me to the throttle stop. The throttle seems to move a lot. I will open the throttle section of the carb and verify if the stop needs to be cut. However, currently the bike seems to cut out or chug just before I reach wide open throttle. Must be cdi rev limiting.

Lastly, this is an off road bike. What's up with the lights on all the time? Need to sell a few bulbs? A switch will fix that in a hurry.

I like the bike. It has lots of torque at the low end <1/4 throttle. More powerful than the wr 250. However, in a straight away, mid range and top end, the 250 would win since my WR250 could rev up. At 1/4 throttle the bike starts pushing against the muffler. I also like the 1st gear for short, technical control. It will be a great woods bike because of power delivery. I just wish it had more power to deliver from stock.

  • simica

Posted December 27, 2004 - 08:54 PM


Your WR 250 has better top end than your new 450? I find that hard to believe. I have 100 miles on my new WR450 and all I've done are the free mods (grey wire, pipe piece, throttle stop, and two uni 1" holes in right side of air box) and in a drag race against my friend's KTM 525 (six speed), we were just about even. I think I backed off before we were tapped out because my side of the dirt road was bumbier than his. But going through the gears we were side by side. I just got a trail tech for Christmas so now I will know what that top end speed was.

  • jdd123

Posted December 28, 2004 - 09:58 AM


In it's current unmodded state it has no top end and I can't compare the two bikes side by side. I just felt that my modded 250 was faster on straights but cannot prove it. I can only say that the stock bike feels like a 250 or 300 compared to the yz450.

The point of my post was what mods are applicable. I am heading to the garage to check out the carb, plug color, and throttle stop. The bike is officially broke in.

  • Texas4play

Posted December 28, 2004 - 11:14 AM


All free mods are applicable: throttle stop, gray wire (in a six pin harness now), exhaust snorkle - remove, air box top - remove, air box sides - circle cuts (if needed). The a.i.s. needs to be plugged or removed. TT member "lowedog" sells a kit he made to remove it, PM him for details. The carb is jacked - fuel screw plugged over - remove with a 180 pick. Carb needle is non-adjustable stock. At a minimum replace with an '04 needle or for the most out of your bike buy the JD jet kit and zip-ty fuel screw. The jets will have to be changed as well because they are lean. And then, most importantly, ride the tires off it because it will scream once you get it uncorked and tuned.

  • jdd123

Posted December 28, 2004 - 11:45 AM


Thanks, especially the heads up on the non adjustable needle. That's a suprise I wasn't ready for. What's up with this silliness from Yamaha? Well if they jetted it lean, and I believe you are right because it seemed ok at my altitude. The bikes when jetted correctly for sea level run rich here. The bike seemed a little lean because of an infrequent bog when first started, but I thought that was because it was soo cold out. By the way that was one good surprise, they use a #50 leak jet and the dreaded stock bog off idle is gone. At least, I don't have to fix that!

  • Texas4play

Posted December 28, 2004 - 01:47 PM


It's like you said originally, "Thanks CA". Green = lean. Yamaha had to do all this stuff to make the bike 50 state legal. The 2005 crf250x has alot more emmision equip and I'll bet the crf450x will have it all too. Yamaha's 250 will probably get epa'd next year. All the manufacturers should kick in donations to Thumper Talk for giving us the information exchange to make their bikes run right!

  • Wayne_Thompson

Posted December 28, 2004 - 02:01 PM


If I am not mistaken, this is the first year the WR has been a green sticker. That will tell you what they must have done to it to make it that way.

  • ges

Posted December 28, 2004 - 02:11 PM


i've heard about the grey that the ignition wire and if so does it make a difference?and how?

  • jasilva

Posted December 28, 2004 - 08:18 PM


I've got an 05 that I'm modding now. As others have said all the mods still apply. As far as the mixture screw and exhaust. The mixture screw is still there you just need to get the stupid little plug out of the opening. Use a dental pick or something similar and push it into the little hole in the plug and pull/pry the plug out. The exhaust can be uncorked by removing the six bolts that hold the end cap on and then remove the 4 bolts that hold the outlet pipe and SA in place. Throw the outlet pipe in the trash and put the SA back. Then get a JD jetting kit and rejet following the instructions(you'll get an adjustable needle in the kit). Now enjoy the bike it will rip compared to a WR250. :cry:


  • Wayne_Thompson

Posted December 28, 2004 - 10:55 PM


i've heard about the grey that the ignition wire and if so does it make a difference?and how?

If not mistaken, the gray wire retards the timing. :cry:

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  • skeener2

Posted December 29, 2004 - 07:36 AM


The exhaust can be uncorked by removing the six bolts that hold the end cap on and then remove the 4 bolts that hold the outlet pipe and SA in place. Throw the outlet pipe in the trash and put the SA back. Then get a JD jetting kit and rejet following the instructions(you'll get an adjustable needle in the kit).


So basically if I get the jet kit I can toss the whole internal sound baffle out?

I figured this was probably the case...but didn't want to lose bottom end grunt just in case. Guess Ill have to get around to getting that jet kit.

I did try to drill out the baffle like on the 250 FAQ. But it wasn't gonna come out. (And yes...I did completely drill out the rivits.)

  • jdd123

Posted December 29, 2004 - 11:04 AM


Well, I opened the carb, put in the zipty screw, verified the non-adjustable needle, and found out that someone completely removed the throttle stop. Thanks dummy, as this leaves a nice little hole for dirt to get into the throttle mecanism. I taped it up and have a yz stop on order. The smog pump irritates me. What a waste. It doesn't make the bike run cleaner, just fools the emmission test by pumping air int the exhaust. This just adds to the restricted exhaust. I did the grey wire mod and noticed quicker response. But the internally that 1" hole inside the muffler, cuts out the top end. That stock muffler has to go. When I get the new exhaust, I will desnorkle it. For fun, I will go back out and try it with the side cover removed.

  • Indy_WR450

Posted December 29, 2004 - 02:00 PM


Dont just tape the hole! :cry: Be careful you dont run the bike without a stop the slide can jam open and it will be very dangerous to handle! You may not be able to reach for the kill switch in time and you may end up in the trees when you least expect it. :cry: I would go to the hardware store and get a metric bolt and cut it down so the slide just opens fully in the throat. :cry:

  • velosapiens

Posted December 29, 2004 - 02:28 PM


What's up with this silliness from Yamaha?

kawi did the same thing with the klx300 needle, and the plug covering the fuel screw. most street bikes (my bandit1200, my gf's xt225, my old klr650) have the same deal, non-adjustable needle and plug covering the fuel screw. i don't believe that ktm has done the same thing (but i don't have a ktm 4-stroke, so i'm not sure), and i have no idea why that would be.

the 'air injection' was also on my bandit. another way for aftermarket companies to make a buck by selling blockoff kits. sigh.... The logical next step will be annual emissions testing and some guy will inspect to make sure the plug is still covering the mixture screw, etc....

  • purluvwr450

Posted December 29, 2004 - 02:35 PM


The logical next step will be annual emissions testing and some guy will inspect to make sure the plug is still covering the mixture screw, etc....

How dare you speak such blasphemy!!!!!!!!!!!!!!!!

  • Parrot

Posted December 29, 2004 - 05:36 PM


Come on let them know you never get in to the upper rpms. You need the low end to have as much torque as you can get. Then you'll have a great time with the bike. It needs to be set up like a trials bike. By the way it is raining here today, and I still haven't gotten the water pump parts yet.

  • jdd123

Posted December 29, 2004 - 06:25 PM


ok ok already, I still like to open it up on the road. Are you suggesting I get a John Deere tractor for dirt bikin'? Hey, that is funny about the rain and your water pump parts. Use a big funnel to catch the rain while riding. Then you would not need the pump. By the way it took me 2 years and 2 bikes to work up to this bike so I am proud. At least you don't hear me whining how a short guy like me can't get his feet on the ground.

For the guy who could not get the insert out. I just removed the insert out of the pipe. After the rivits are drilled out, I used a needle nose vise grip and a hammer. You have to pull it straigt out in the direction of the exhaust. It is in very tight. The bike wasn't significantly louder with it removed but it did run better. Haven't tried the no tail pipe for fun.

On the throttle stop, thanks for the warning. I almost forgot about the stuck problem. They completely cut off the stop on my old wr250 and I had to order a new stop. I will warn my dealer since they grabbed the bike from another dealer for me. I have a YZ stop on order (arriving next week) and am careful not to pull the throttle hard at the end. Per Parrot's jab, I normally don't wack the throttle so I am ok.

I was wrong about the muffler. I looked in the arrestor chamber in daylight and saw that in addition to the 1" hole at the start, there is a 1" tube that runs on the bottom and is open at the rear of the chamber (rear of bike). So it is not as restricted as I thought.

After finally deciding that I am not going through deep water and to remove the snorkle. Of all the silliness, I cannot get the snorkle out past the battery clip. I have the battery out but am afraid to crack the plastic box that holds the battery.

The bike is responding much better with the mods. (grey wire, throttle stop, exhaust restrictor). I may even leave the stock exhaust. The bike will be great for mountain trails and when it gets up in the high altitude, there should be enough excess power to go where I want.

  • mtrablue

Posted December 29, 2004 - 08:46 PM


just use a small screw driver to help get the snorkle over the clip. don't worry, we've all done it.

  • Gadsen

Posted December 29, 2004 - 10:01 PM


If I am not mistaken, this is the first year the WR has been a green sticker...

Actually, the 03 and 04 WR450F are the ONLY years to not be green sticker. Its funny how they have to make it emission legal for an "off road competition" motorcycle. I wonder when they will start cracking down on NHRA :cry:

  • chiefsfan.58

Posted December 29, 2004 - 11:14 PM


Hey Skeener, I was able to knock the insert in the exhaust out with a hammer and a long thin punch. Just lighty clamped down the end cap in a vise and inserted the punch thru the inside of the end cap from the side that goes into the can. tap a lil' on one side, then the other, basically back and forth until enuff is protruding out the outer tube that you can clamp a pair of vise grips on it. Then it is easy to just tap on the edge of the vise grip and it'll be out in no time. I took a little extra time and gas welded up the two holes from the rivets (three minutes to get the torch out and the rod, and about 10 seconds per hole to plug em up). hope this helps.... :cry:


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