250-500cc 250 / 300 / 360+ Jetting Database

Here is a question for you needle gurus. After switching to the Gnarly pipe on my 09 WR250 I have run into a snag. If I run the needle 1/2 step up from the middle it rips off the bottom, idles perfect with a 30 pilot or a 32.5 (better with the 30) but has a rich spot and stutters at about right as its coming hard on to the main. If I lean the needle by removing the 1/2 step washer and let it ride in the 2nd notch it rips from mid to top but looses some bottom to 1/2 and feels a little lean + won't work at all with the 30 pilot because it's too lean. I could go to a 35 pilot but would load up at idle and still be lean/lazy from 1/4 to 1/2. My current needle is E16BFY43-74. I'm thinking that if I had a needle that had a 1/2 step taper richer on the bottom I could leave it in the 2nd groove and have the best of both worlds. Or possibly a 1/2 step richer on top and then put it in the middle groove. Can someone direct me to a Mikuni needle chart or does a needle like I'm describing even exist? BTW I'm being extremely picky here but since I know how good this bike runs when it's perfect I'd kind of like to have the fun of getting it dead nuts.

My 2 cents is; I have the same bike and ride roughly same elevation. I ride in the desert, lots of sand washes and two track. Mine seized with the needle in the third position where Husky put it and had lots of pipe drool. It ran pretty good with a 410 main and the needle (the needle stamped gay) on the bottom position (full rich). I am now working with JD Jetting to help him come out with a jet kit for these bikes. I am getting pretty close to coming up with something that I personally like for my kind of riding, hopefully when done it helps others too.

I have heard of a 1/2 step washer but can.t find one. I measure the different needle positions at .020 so I need a .010 washer that fits. I found a .030 washer and thought about using that and moving the clip up one but when I put it in the needle was ridged and that mad me nervous to try. Have you found a .010 washer that fits?

I wonder if a JD needle would help ya. Not sure if you can buy from them separately, or just in their kit.

Have you tried the needle in the 3rd clip?

Yamaha YZ125's use the BFY series needles. If you look in a parts lits for a 2009 YZ125 you'll see like 15 different needles.

Or you could try the GAY needle that comes on the 300's. It is a much straighter taper on the end of the needle.

They GAY needle may be close to what I need but it only comes is the Husky power up kit for about $80.

If I new how to read the numbers on the Yamaha needles I could probably pick the right one. I was told the GAY only comes in the factory power up kit but maybe there is one out there from a Keihin convert that would sell it separately.

Oh ya and I did try the 3rd clip and it rips on the first 3/4 then rich stutters a bit and then revs out.

Right at 3/4 is where that steep taper is. I'll post more of the info I have gathered on these needles in the Jetting Chat Thread.

m2011 wr 300 has seized twice in the last 3 weeks. with similiar jetting. what gives???

air leak around reed valve intake??

Just remember that this thread is a guide and not gospel or avenue to rubbish other people's settings when your bike comes a cropper using someone elses settings.

Seized..please elaborate as you can cold seize a bike (don't warm up the bike, or incorrect piston size, and the piston expands unevenly, locking itself to the cylinder) or a lean seize (running at or close to WOT and the bike locks up which the top of the piston will be melted).

Mine seized with the stock jetting while riding fairly hard on a sandy 2 track trail with stock jetting. (45 pilot, gay needle 3rd position, 420 main) After rebuild I ran with the same setup but with the needle on 4th position and it survived that same trail. I have since been working with JD Jetting and he has come up with a new needle jet and needle that I personally like very much. After the seize, I have been a little gunshy so since I am running it on pump gas I am trending on the rich side. But I can say it is much faster now at any given throttle opening than stock.
My motor melted the piston front right (as sitting on the bike, say 1 o'clock) at about 1/3 to 1/2 throttle. With no evidence of detonation. As mentioned above this is only my opinion and others may not like it but I like my new setting very much.

How about jetting for a stock 09 WR 250 ice racing at 1300 feet and 30 degrees with Mikuni carb. thanx.

Paging Johnnymannen

I got my 09 WR250 running about as good as I think it could possibly run (see post 38 on this thread) and then I smashed the stock pipe on a tree. I bought a FMF Gnarly and it changed the needed jetting quite a bit. I'm really happy with how it is now after a few rides and some changes as follows.

Year & Bike Model = 09 WR250
Carb = Stock Mikuni
Pipe & Silencer = FMF Gnarly with stock silencer
Other engine mods = none
Gearing = 13:50
Premix ratio & fuel type = VP 110
Temperature range (deg F) = 60 F
Elevation (feet) = 1500
Main jet = 430
Pilot jet = 30
Needle = GAY
Clip position = 4th
Air screw setting = 1 turn
Slide = 4.0 stock
Conclusions/Results = There is a good bit of gain to be had on the top end with the Gnarly pipe without losing any mid. Also with the above set up I was able to get away with mixing the VP 110 with no alcohol pump 91 @50% with no problems which is something I was reluctant to do with the stock needle because the steep taper left me with a slight lean spot that could have caused some detonation. The mid is really crisp and I'm sure if you wanted to tame it down a bit you could raise the needle to the 5th clip but I kind of like how it gets on the back wheel quickly in 3rd and 4th gear at 3/4 throttle. If you were a fast A rider and wide open most of the time a 440 main would work well but in the woods I can rarely sustain wide open for very long so the 430 is just right for me because it stays crisp in the transition even after long sections of tight single track. The Gnarly pipe is worth the money and I recommend not waiting until you smash the stocker to try one.

Nice report Doug.I finnally got to ride my new to me wr250 last weekend. Base camp was at 1700 and we rode to 5800 temps were 45to30to50 and the bike ran good with the 6BFY4374 IN THE #2 POS. 30 PILOT W/400 MAIN. I went to richen the clip after riding in a bunch of snow and bent the needle tip trying to put it back in the carb so then I ran it in the #1 pos bac to camp and it still ran good.Were u able to get the gay needle by itself? I called MotoXotica and Bill's and they told me it only came in the power up kit. Would you try the stock pipe w/ the gay needle?BTW no exhaust spooge the whole ride. I havent looked at the plug yet but I think I'm gonna try a 410 with the stock needle in the middle.My only real complaints about the first ride are the draggin ass clutch,kick stand and, it was hard to find the rear brake sometimes.

Halls Cycle had the GAY needle by itself for $11. It looks like you and I came up with the same results with the stock needle except you are at a slightly higher altitude.

I am running a 38 mm Keihin I got from Motorsportz with the jetting they sent it out with 175 mj, 45 pj. I think it is correct. One difference, I am running the JD Red needle 2nd clip from the top that was provided with the carb. Also running 2 - Power Nows for and aft of the slide.
Motor stock. Pipe is Gnarly. Leo Vince Silencer. Temps right now have been 45 - 55 degrees. I suspect I will lower the needle another clip when the warmer weather comes and maybe go down a step on the jets.
Bike runs crisp and strong just a little off idle and a good way up towards the top. Great power band.

Year & Bike Model = 2010 WR 300
Carb = 38 PWK Air Striker
Pipe & Silencer = FMF Gnarly & Q Stealth silencer
Other engine mods =
Gearing = 13:53
Premix ratio & fuel type = 60:1
Temperature range (deg F) = 60 to 80
Elevation (feet) = 500 - 3000
Main jet = 170
Pilot jet = 42
Needle = JD Red
Clip position = #2
Air screw setting = 1.5
Slide = Not sure, what ever JD installed.
Conclusions/Results = I've tried by trial and error many settings, however these settings are the cats meowwww. Many people have probably found that the FMF Gnarly pipe is flat on top when they do the switch, don't believe it entirely. The problem is the Q Stealth silencer that I run; it's very restrictive thus the silencer has problems clearing if the main jet is too rich. I thought my pipe and silencer combo was to blame for there being no overrev; not true. I went to a smaller main jet and now this pipe and silencer combo is beastley clean and crisp from bottom to top; mine has tons of overrev now. I also do like clip position #1 or top position.


Marvin Fredrich