08 wr450 carb removal requred?

(Gentlemen) and I use that term loosely (or ladies), I am curious if any of you know the easiest way to get to the carb on an 08 wr450, I need to do some jetting changes and after walking out and looking at the carb I have postponed the ordeal more times than I care to admit. Is there an easy way to get to it? Or some trick that will make the ordeal painless? I hate to remove that airbox etc etc if there is an easy alternative? A step by step would be helpful if its complicated thanks for your help.. Rob


Depends on what jetting changes you need. Main jet, pilot jet & needle changes are all straight forward without removal. Leak jet is a little bit 'fiddly' but again, straight forward, with the correct tools.

main and pilot but it dont look like it can be done with carb on... its so congested grrrr

I use a little flat mirror that I lay under the carb.

Then you can see what your doing.

And adjustable leak jet means you don't have to take the bowl off to adjust that.

so I should be able to do the main AND pilot through the 17mm bowl nut?

so I should be able to do the main AND pilot through the 17mm bowl nut?

Its much easier IMHO to remove the rear shock and take the carb out. Sounds harder than it is. Once you do a time or two its a breeze. You will be glad you did. At least I was. Good luck

so I should be able to do the main AND pilot through the 17mm bowl nut?

Yup. Shorty screw driver on the pilot. Beezers suggestion of the mirror helps a lot. To easily put in the new pilot, use a short length of vinyl tube that fits snuggly on the pilot. Stick it up and twist, gently final tighten with a screw driver. I also put a towel under the carb to 'catch' things.

I only pull the car when I have to pull the bowl. Even that can be done on the bike but I hate if a float pivot pin falls and gets lost, so removing the carb makes it easier.

I thought about changing the main and pilot, Im not a racer but I have added a white brothers xcr slip on grey wire mod, and snorkel out of the airbox so Im sure its running lean, (harder to start after slip on addition) Im not sure if I need to mess with the needle position, leak jet etc etc or if just changing the pilot and main will work. I have zero bog (next to zero anyways) bike seems to run well but again Im a trail rider on a 450 so it ran good to me by just changing the pipe. I dont really feel all warm and fuzzy about messing with the needle or tearing the carb apart, jets I have changed in my smaller bikes that I bought used and Im comfortable with that, can I just change the jets? Do you guys think it will need the whole JD kit? what size is recommended for 1000 to 4000 feet and 60 to 80 degrees? sorry for the small book Im writing...thanks again

throttle stop removed as well...

According to the jetting gurus Im thinking 168 main and 48 pilot?

Edited by wanawakeboard

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

Be sure to keep notes of your settings. You may find you need to make a change, say if you're riding in the mountains or down at the beach. Returning home, it is a simple matter of referring to your notes to restore things.

Main Jet

Starting with the recommended main, remove the airbox door and go for a ride (bike fully warmed up, 3rd or fourth gear, up a slight hill). Is it better or worse?

If it is better, you need a smaller main.

Go down one size, replace the airbox door, ride. Remove the airbox door and test again. Better or worse? If better, go down a size again. Keep repeating this till the test with the airbox door is worse.

If it was worse with the airbox door removed, tape over 1/3 of your airbox opening, test (airbox door on, of course).

If it is worse now with the tape and was worse with the airbox door off, your main is just right. You are done!

If it seems better, you need to go up a size in main jet. Then test it again (remove the tape). Replace the tape, test again. If with the tape on it is better, go up another size in main. Keep repeating this till having the tape on is worse than with it off.

To finish up and ensure you are set accurately, retest the bike with the tape off (airbox door on), ride it, then remove the airbox door (tape off, of course). Best performance should be with the airbox untapped, airbox door on.

Remember, the main only operates at WOT. Ideally, you want to be in 3rd or 4th gear doing the tests, hitting max revs (just shy of the limiter) for at least 10 seconds to get an accurate representation of the jet status.

Be sure to keep notes of your settings. You may find you need to make a change, say if you're riding in the mountains or down at the beach. Returning home, it is a simple matter of referring to your notes to restore things.

The Needle:

First, confirm your TPS is adjusted correctly per the manual.

To do this, you need to mark the throttle grip. I place tape on the grip and a piece on the throttle housing. I make a mark on each. I open the throttle completely and then make a mark to correspond to that. Then I make a series of marks at 1/2, 1/4, 3/4, 1/8,3/8, 5/8 and 7/8.

Again, in third/fourth gear ride up an stead incline each time at one of the positions, make notes on how it runs at each.

If there are running issues in the first 1/4 throttle, you will need to try a different needle, one where the last letter is different. As you go up in the alphabet, you go leaner.

If there are running issues above 1/4 throttle, that deals with needle taper, length and clip position. Often just moving the clip will sort things. If a different needle is needed (say you ran out of positions) the second to last letter is what is changed. A letter is typically equal to a clip position, so an one letter change is like moving the clip on spot.

Remember, dry sounding or flat (not a bog, just flat/lack of power) is lean. Wet, misfires, heavy is rich

I have an 09 wr450 and need to take out the throttle stop but don't see a way to get to it either.Do you have to take off the carb or subframe?

A couple of extensions and a swivel will easily do it on bike.

Yea when they did mine they used a REEEALY long screwdriver from underneath... that part was easy, thanks william!

I can change the pilot or the main jet in 1 beer.

I go right through the float bowl access plug.

If you take a chinese screwdriver and twist the blade right near the tip you can get it to hold the pilot jet on the end of it. I used a vice and an adjustable wrench.

Makes changing the pilot jet a breeze.

I can change the pilot or the main jet in 1 beer....

You must be a slooooooooow drinker........:thumbsup:

Or a really fast jet changer?

Maybe by irish standards I'm a slow drinker but............

I was totally unaware there was a main jet AND a pilot jet in a beer.......

You can build an entire pink elephant if you add enough bottles of beer! the trick is to drink enough beer to Accomodate the mass and specific gravity of said Quadruped, drink drink drink til she flies...lol

I was totally unaware there was a main jet AND a pilot jet in a beer.......


I'm not in a real big hurry to leave the garage anyway being married.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now