WR jetting with mods: What is your's?

OK. I have finally determined what I suspected is true: The guy I bought my bike from DID do some jetting changes. He apparently went even richer on the main and pilot. Having completed a long-overdue list of mods all at once, I am now rejetting and would like to be in the ballpark when I fire up the beast and experience the "holy sh**!" factor to it's fullest. :)

My '99 WR400 had a 172 main and a 48 pilot and fuel screw 1 1/2 turns out with just the throttle stop and airbox-lid mods. It always left the plug black and sooty but started reasonably well and made more power than I can handle (but when did that ever stop us from tinkering? Too much is never enough! :D). I live in Iowa, so not much elevation and our temps this time of year vary greatly on a day to day basis from low 40's to high 80's. Soon, it will be just plain hot and muggy.

It now sports: custom YZ450 exhaust cam (Thanks cw !), grey wire unplugged, Big Gun exhaust (tapered headpipe and Race Core), a P-38, a YZ OBEJP needle (middle 4th position), and the JamesNow mod. I have not fired it up yet since doing these.

I am working on trying to do a version of Garret's fuel screw mod right now, too, before I put it all back together. I would like to jet to run easily obtained Amoco Ultimate 92 octane gas. I have read many posts where the jetting and plug condition changes with the type of gas, so I thought I had better mention that.

The book I have says stock main was a 168 and the stock pilot was the 45. These bikes were reputed to be rich from the factory, so I don't know why the previous owner went even richer :D. I figure the much better flowing BG exhaust will lean things a bit by itself, and the YZ needle should, too. I don't want to toast the motor by going too lean right off the bat, but I don't want anymore black sooty plugs either.

I was going to return to that stock jetting (168 main/ 45 pilot) unless one of you experts advises differently? I have a few other jet sizes on hand that I can play with: 172, 170, 168, 165, 162 mains and 40, 45, and 48 pilots.

I trust Yamahadude's advice to start from stock using a YZ needle. So now that I have found out what "stock" actually IS, that is my current plan. I am curious to see what some of you guys with similar mods are running, though... :D

You have turned you're bike into a YZ now, YZ stock jetting is the basline that you're looking for not WR. I have YZ jetting in mine and should be a safe start if you are within a couple thousand feet of sea level and the temp is relatively mild. Exception, my starter or choke jet is still WR spec, the bike still starts great cold with choke on so I didn't change it.

Thanks Chris! That makes very good sense since it really IS a WZ now! :)

Try my signature............


Wow! Compared with those numbers, I guess I'm in no danger of being too lean with mine! I have always been curious as to how well the "Taffy jetting :worthy:" worked out for those who tried it. If you like it, that says a lot. Do you happen to know the part number for that EMM needle, Bill? My parts man tends to be a "year, make, and model" kind of guy... :)

Oh, and is that #2 position from the top or the bottom of the needle?


Im using the same settings as Bill (he recommened to me a few months ago) and the bike flat out rips now.

You can go to Sudco.com and get the EMM needle or anything else you want. They have it all. :)

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