New 2008 WR 450 Grey wire = Bog

I just bought a new 08 wr 450. I am waiting on my pipe, and fuel screw, but tonight I decided to install some of the parts that did come in. One of the things I did was remove the Grey wire and instantly the bike ran like crap from idle to about 1/2 (of 1/2 throttle since I haven't installed the GYTR kit yet) throttle. Why would this happen???????

All other restrictions must be removed before the grey wire mod will work. Especially the throttle stop screw/ half throttle screw.

You are trying to use an ignition map that is designed for a fully unrestricted YZ450. You have a fully restricted WR450 so the ignition map isn't compatible.

If I was you I'd reconnect it until your other parts arrive :worthy:


Already did. Thanks for the reply. I have the GYTR kit, but no muffler, so I am waiting on that. I am also waiting on my Zip-Ty fuel screw. I want to take the ass end of the bike apart grease everything and do the carb mods all at the same time.

The Grey wire did not instantly cause the bog.

But...... In any case, you need to confirm that and find the exact cause. Re-connect the grey wire. Did the bog go away or is it still there? If you made other changes, reverse them one at a time till you are back to stock, testing after each reversal. If the bog goes away, you know you found the cause. Then let us know what change was the culprit. If you revert the bike back to stock and the bog is still there, then you knocked something out of wack.

Actually it did. The wire is the ONLY thing I changed, and it went away as soon as I re connected it.

That is the first I have ever heard of the Grey wire creating a bog. I am at a loss to explain. The difference the Grey wire makes to the ignition timing is very slight and the effect is more apparent as RPM's increase.

A bog was a very simple explanation. A more detailed description would be very poor idle, stumbling at low RPM, and would clean up as soon as 1/3 and above throttle. Basically it ran very poor down low.


I live in Vegas, and ride from 3,000 to 8,000 Ft. Temps anywhere from 60 F to 95 F.

Mods I am planning:


FMF Power Core 4 Slip On

Twin Air Filter

Air Box mod

Zip- Ty Fuel Screw

My question is doesn't the jet sizing that the kit came with (a 175 Main and a 50 Pilot jet) seem to rich? Comparably set up bikes seem to be using 168, 45 jets. Should I wait to pick up some smaller jets????

Thanks in advance.

Attack each issue individually. Start with the idle.

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.

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). 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.

Now that that mess is out of the way, comes time to experiment with the needle. You'll want to mark the throttle grip to enable you to know truly where on the carb range you are. Start with the rec. settigns for the needle you have in the kit, report how the bike behaves at 1/4, 1/2 and 3/4 throttle.

Now, once you have the main jetting issues behind you, then and if there is a bog we can can work on it.

The 175 main may be Ok with your open pipe. I'd want to have a 180 down to a 160 on hand to test.

I think the 45 pilot should be right and possibly smaller (esp. with a ZipTy fuel scew-far from my favorite-I hate alloy ones) so you may want to have a 45 down to a 38 handy.

Thanks!!!!! William,

I have the bike torn apart. Greased the swing arm, linkage, removed baffles in air box. I am waiting for the pipe, air screw, radiator braces etc.. which should of been here already. I guess I shouldn't have ordered those parts from Thumper Talk LOL. No, I am only waiting on Rad braces, and skid plate from here, but I wish I would have known that they don't make the braces or skid until an order has been placed.

I really appreciate the detailed instructions and help. I will let you know how I progress as soon as I can.

Thanks again!!!!!!!!

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