Should I do the BK?

7 replies to this topic
  • yamaha426

Posted May 23, 2002 - 07:56 AM


I got my 02 426 about 3 weeks ago and for the most part it runs extremely well. The only times I have any problems I have with it is when I stab the throttle up to about 1/2 throttle, the engine stumbles for what is probably one engine revelution, puts out a small puff of black smoke that you can barely see, and then runs fine. I turned the fuel screw in about a 1/2 turn from where my dealer set it. Everything on the bike is stock and will probably stay that way as I am going to college this fall. This is not a real big problem, I was just wondering if I should do the BK mod or take it to the dealer to have them work on the jetting. I do not have any doubts about my mechanical abilities, I can do it easily, I am just not that sure about carbuerators.......see I don't even know how to spell it. Even if I don't like it the BK mod can be undone with no side effects, right.......just remove the screw and it is back to stock settings. Also any help any of yo southern Idaho guys could give me on jetting would be great......I live in Glenns Ferry, about half way between Boise and Twin Falls.

  • skthom2320

Posted May 23, 2002 - 07:59 AM


Turn the fuel screw in until you get a slight popping on deceleration. If you get a hanging idle or you go less than a 1/4 turn out, then put in a smaller pilot jet.

  • yamaha426

Posted May 23, 2002 - 08:04 AM


I forgot to put thats that that I did when I turned my fuel screw........I am fairly sure that it is close to where it should be, also my the last time I pulled my plug out it was really black.....but it was also soaked because one of my brother's friends had flodded it.

  • John_Lorenz

Posted May 23, 2002 - 09:11 PM


Checking the plug in your case would not tell you anything [QUOTE] but it was also soaked because one of my brother's friends had flodded it. /QUOTE]
Next time your friend touches the throttle break his fingers :)

How many hours on the bike so far ?
If the bike is still stock then some simple changes may only be needed. There are alot of threads here with regards to proper jetting and setup for the 02's.

BKmod is a debatable question, but I would say if it were me I would do it.

Next Question
How comfortable are you in tuning / jetting and general tweeking of the bike ?

Hey yz-n-limbo is this one ok for an answer :D

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  • yamaha426

Posted May 23, 2002 - 09:38 PM


Well, so far my bike probably has about 10 hours on it, and although I feel comfortalb ewith working on my bike I just don't want to ruin anything as I have to save as much money as possible for college. I hope that I will be able to fix my irritation (not really too big of a problem) by just re-jetting it. We are coming up on summer here and in a few weeks the temps will range anywhere from 95-110 with 20% humidity at the most, I am not sure but I think that our elevation is just under 3000' and I ususally stick pretty close to that. Thanks for you help.

PS- I wanted to just give him the 426 treatment next time I caught him out in the driveway.........but my mom would probably not be too happy. Now I just hang my helmet on my throttle. :)

  • John_Lorenz

Posted May 23, 2002 - 09:45 PM



My suggestion first would be to search the archives here for Bog "There Is Plenty Of Reading Material"

The BKMod will run you about 12 bucks for material
Drill, 5 mm Tap, 5mm Bolt and spring
and a couple hrs of your time heck make it an adventure call it a day.... Take your time.....

you can get detailed instructs at motomans site
Look for Technical then BKmod

Jettig will cost a bit more: your elevation / humid and temps are about the sme for me in Calif.

I am running on a 00 426
Pilot = 45 (Stock 42)
Main = 168 (stock 163)
Air Screw / Pilot Screw is = 1 3/4 turns out
Needle Clip is one down form Stock (Raises Needle)

Thats what I have, thi smay not be what you need not sure maybe a combo of, But like I say read the threads there are good info there
BKmod = .5 Sec Duration

  • yamaha426

Posted May 23, 2002 - 09:49 PM


Hey thanks man I might call my dealer and see what thy say, I know the guy really well and he will most likely fix the jetting for free. But I might end up doing the BK mod since it can easily be undone. Thanks

  • 98yz

Posted May 23, 2002 - 10:58 AM


You might just check the pump timing. I removed alot of the crack of the throttle hesitate by just that. Then I did the BK mod and timed to .5 sec, and it is smooth from off idle to full throttle.

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