All 2st Jetting Chat - Need Help? Post Your Questions Here

I think I might be missing that washer (WR250 2006 TMX38), I don't see it in the partsplan, are you sure it needs to be there?
My WR250 just had a topend rebuild, has decent compression, but as lacking power, especially in the low end, wheel lifting is pretty hard (13-48 gearing).
The sparkplug is a litlle wet, so I'm guessing it's somewhat rich.
I'm living at 250meters and have a 32,5 pilot with 420mainjet, I believe 3.0 slide, clip in the middle (third slot?) and tried various settings on the air screw (which is now 2 turns out), stock except the HGS pipe.

Regards, Bart

Lankydoug,

Here is some more info on the WR250 BFY needles. The stock needle being a 6BFY43-74, the 74 is the starting diameter as in 2.74mm, a -73 would be a 2.73mm starting diameter which is thinner and would be a richer needle. I haven't figured out exactly what the 43 represents, but from what I have gathered I believe that a 6BFY44-74 would be a 1/2 clip richer needle than the 6BFY43-74. A 42 would be 1/2 clip leaner. I believe the 6 at the front of the code is the length series as in 6x.xx mm long. The stock needle is 68.965mm long. The BFY are the codes for the taper angles. B=0*15", F=1*30", Y=6*15". I think they go through the alphabet in 15" increments. This is what I have gathered from searching as much as I could and taking notes overthe past few years. I think it is correct, but if it is not I hope someone will let us know.

It may be that a 1/2 clip brother to the stock needle may be what you need, but if you have been trying different settings with 1/2 clip washers, maybe not. Maybe a different diameter may be worth a try. Maybe you could get a couple different YZ needles to try. I thought Halls sold me just the GAY needle, but it was awhile ago so I forget. I measued both needles and the GAY needle is close to the BFY up to 1/4 throttle. Then it is 0.15mm thicker at 1/2, 0.13 thicker at 3/4, and 0.1mm thicker about 6.5mm from the tip. The other difference is the GAY needle has a smooth taper vs the steep one about 12 mm up on the BFY. I liked the way my bike ran at elevation with the GAY in 3rd. If you get the GAY needle I would recommend trying it in the 4th at your elev. I know the BFY works well in the 2nd for me and I look forward to testing them back to back this spring when the temperatures are warmer.

Another thing you may want to try is just a different main jet. If you had it running well before the pipe change with the stock needle and now it has a rich stutter over 3/4, maybe a leaner main would do it. From my measurements, it appears that the sharp taper on the BFY is right at 3/4 throttle.

Really good info here, thanks. I did have to lean out the main two steps with the new gnarly pipe, I went from a 410 to a 390. I think what I need is a different taper since I can either get it perfect on the bottom and rich on the top or perfect on the top but lean on the bottom. I just need to figure out which needle will accomplish this. Many people would ride my bike as it is and think it's perfect but I know it can be better if I had a needle that would effectively richen the bottom 1/2 step while leaving the top as is (in the 2nd groove). Or a needle that would lean the top 1/2 step and leave the bottom so that I could run it in the middle clip (3rd groove).

I wish I knew where to get these OEM three letter code Mikuni needles, but I haven't found a source yet. I would suggest searching on different model two stroke OEM parts lists like on cheapcycleparts.com, and estimate if the tapers and diameters would be close to what you're looking for. Out of curiosity I just found a few:
02 CR250 Honda - 6BEY30-74
02 CR125 Honda - 6DFY5-74
06 CR250 Honda - 6DGY26-65
06 RM125 - 6CHY17-64 (I think some are using this series on the WR125's)
02 KX125 - 6BEK2-71

6BFY43-72-3=2.72MMRICHER
6BFY43-73-3=2.73MM
6BFY43-74-3=2.74MM STANDARD
6BFY43-75-3=2.75MM
6BFY43-76-3=2.76MMLEANER
STRAIGHT PORTION DIAMETER IS THE 2.72 AND SO ON.LAST DIGIT IS CLIP POS.
TIM.

Since my stock needle is lean on the bottom when it's right on top that tells me it needs more taper. A 1/2 step on the clip will reverse the problem so that tells me that if I had more taper that would effectively change the diameter equal to 1/2 step richer at the bottom yet remain the same at the top I would have what I need. It amazes me how sensitive these are to needle changes but if we could get the fuel curve to match what the engine wants it would be a ripper at any throttle position at any rpm + idle all day and start 1st kick.

This reminds me of setting up alcohol fuel injection systems and matching pump size to nozzle and bypass size to get the right pressures and fuel volume at all rpm ranges, only it was easier because mechanical injection behaves the same no matter the air density.

Do all these needles have the same taper but the variable is where the notches are machined to effectively change the needle height?

IDK,all I recongnized so far are different diameter in the straight portion and different clip pos.
Tim.

The starting diameter is the only variable in 464x's example. The tapers would be the same. If you want a different clip position, then I think an example would be:
6BFY43-74 (3rd clip pos) = 6BFY44-74 (3 1/2 clip pos)

So by variation of the 43 number you change needle height, and by variation of the 74 number you change starting diameter. Then it gets fun thinking about what will happen when you change both. Since you have 1/2 clip washers you may want to get a 73 (richer) and a 75 (leaner) to try.

Here's another thread that should be linked here - good stuff
http://www.cafehusky.com/threads/various-tmxx-needles.22569/

Here is a little info http://www.sudco.com/vol33/56-59.pdf

Chad Thompson @ Sudco promptly answered an e-mail and said that "Sorry, the carburetor that comes on your Husky is an OEM only carburetor and the only tuning components that are available to me are the main jets and pilot jets. Needles are dealer items, that carb is also used on Honda CRs, Kawasaki KX125s and Yamaha YZ125s. I do not have an resources or specs on those needles to be able to help you."

Now I at least know what other factory needles to look at besides Husky

I looked a bunch of them up last night.
http://www.cafehusky.com/threads/various-tmxx-needles.22569/

I ordered a GAY needle from Halls $11.00 it is a leaner needle so I will try it with a bigger pilot and a bigger main and jet from there.

i think the main variable would be pv opening in relation to taper, does any body know at what rpm the power valves should be opening?.

The GAY works well in mine with the same Main and Pilot as the BFY. It's just one clip lower. Let us know how it works out. I would try just the needle first before changing anything else. But then I am at elevation, so your results may be different.

I'm hoping it will allow me to run a bigger main without the 3/4 stutter. The mechanic at Halls has a 2010 uses the BFY middle clip with a 430 main and a 40 pilot. If I tried that I would need a new plug every day. The main difference is he uses a pro circuit pipe and I use the gnarly

Did you try the new needle yet?

It's installed in the middle clip with a 420 main but it's been cold here, I should get a chance to ride some for the next 3 days so I should get it sorted out. Although it is a compound angle needle it has more of a straight taper than the original BFY.

GAY ride report

Ok, I rode for about an hour with the GAY needle in the middle clip, 420 main and a 32.5 pilot, air screw 1 turn. It was 37 degrees F with clear skies so the air was really good. This needle was an improvement over the BFY with the Gnarly pipe. Keep in mind when I had the stock pipe the BFY was great but the bike flattened out on top, then once I added the Gnarly pipe the BFY forced me to live with a rich top end or a lean bottom end. Now the bike tops out much better than the stock pipe but the real benefit is with the Gnarly and the GAY needle is the mid pulls really hard all the way through with no stutters or lean spots and it's a smooth easy to control pull not a hard hit that has you lifting or looping out. Just for kicks I would short shift it in to 3rd or 4th and slowly roll on the throttle and it would slowly raise the front tire in a real controllable wheelie like you would want if going through a section of whoops. There may be a little room for improvement by going to a 35 pilot and a 430 main but I'm not going to try that right away since I wont be riding on many days when the air is as good as it was today. I'll wait until a not so good air day and see if I think it wants more fuel. This is the most rideable electric power my bike has ever had and I'm really glad I tried the GAY needle. (that just doesn't sound right lol)

How about an 09 WR 250 jetting for ice racing 1300 ft and 30 degrees with stock Mikuni, pipe, and silencer? thanx