2000 BK mod settings?

I spent a couple hours today tuning, and I ended up with these settings:

-168 main

-48 pilot

-stock needle in 3rd clip from bottom (1 richer than stock)

-pilot screw at 1 turn out

-pump delay just misses the slide

-accel pump squirt @ .5 secs

-STOCK exhaust (anyone that can out ride the stocker better be getting paid!)

Of course, I am in south texas, basically sea level, and about 65f today. The throttle response is much better and it pulls very strongly, but I still get a bog off the bottom if I completely and VERY quickly open the throttle all the way from idle speeds. I am hitting VP tomorrow to track test it, I spent 20 minutes running up and down a dirt road today, stopping to play with the pilot screw, trying to eliminate all the bog...but it seems a natural thing for a big bore stroker to have some bog if you completely open the throttle at low rpm?

Anyway, I was just trying to get some input on what other riders in this area are running as far as jetting on 2000 models with the BK mod.


Originally posted by therapture:


*is there anybody out there?*

bumpity bump


I'm also interested in the info your looking for. I just finished the BK mod. on my 01-426 and I'll take all the information I can get a hold of. I guess we'll wait together. :):D

Guys - I too just finished the mod - I'm set at .35 sec on the duration now - was like 3 seconds!!!!!! (yes - missing the slide as well).

I have to take a look at my CB key (2000) model - after that I'll take her out to see what difference the mod has made.

INTERESTING!!!!!!! I have a P38 on my barb - you know, the Factory R&D part that was supposed to eliminate the bog by reducing the pump rod travel - it did reduce the travel on the rod, but the bog never went away. I changed back to the stock cover a did the squirt test, but there was less than .5 sec difference. So I put back on the P38

Thought -- With the corrected BK recommended parameters in place, and if the bike STILL bogs - that is where the remapped ingition would come in. AS we know well by now, the carb re-calibration and the remapped ignition are the fixes now on the 02 models.

Let's try to keep this thread active - It'll be a week or so before I can my bike out for the test run.......

Good luck to you guys - keep us all posted.


I also have done the mod. But it is still abit cold and muddy here in Minnesota for me to get out and try it. I didn't change any jets yet. If I do, will I need to change the air jets too? Do they get changed hand in hand with the gas jets?


my jetting is very close to what your running! I am at 168 main, needle 3rd clip (1 clip richer than stock), 42 pilot (1 3/4 turns out) pump duration at .3 secs! I tried the 48 pilot and the bike was easier to start but felt sluggish...I went to a 42 and it feels crisper. I think the 45 @ 1 1/4 turns would be very close. But since summertime like weather is a month away or so I am sticking with the 42. Later,


Well, I have some very good news. The bike ran absolutely GREAT! Temp of 65f and moderate humidity, this baby was PULLING hard, even my pops noticed the deeper exhaust note...

Before the mod there was a double stepdown I was having trouble doing because my top end was flat and the jump requires a 3rd gear approach, in a slightly sweeping corner, and 4th is not an option because you have to have last second hard acceleration to get the boost. Hardly anyone jumps the whole thing, it is a technical leap, and today only 4 riders were doing it. Before, 3rd gear would not rev out far enough because apparently it was actually LEAN on the top using the stock 162 main. Today it was easy, I had it dialed, this is almost like having a new motor! I could just roll it on in the cornerwhile standing up, then nail it on the takeoff ramp and cleared it easy... I actually found the rev limiter a few times...it would never hit it before...

The bottom end is mucho better, I was able to use alot less clutch work in real tight corners and 2nd gear was primo. I might have to try a 45 pilot, but the 42 is definitely lean on my bike, it will pop on decel.

Slightly faster corners 3rd gear was a real option, the torque was there even better than stock, and there were two sections I used to shift to 4th, but now I can just let her rev out and run it into the next corner. Less shifting hooray!

Also, starting is vastly improved (what's a hot start button?) and the entire powerband has been increased in width. If you have not done this mod on your 2000 and up 426, I HIGHLY recommend it! The hassle of jetting it properly is worth it.

To reiterate my settings for 65f, I am using:

-2000 YZ426, stock exhaust

-168 mainjet

-48 pilot

-pilot screw 1 turn out

-stock needle at 3rd position from bottom (1 position richer than stock)

-pump spray just clears slide as throttle opens

-spray is set at .3 to .4 seconds (as close as I can get it)

-VP 103 octane race gas (nicer response and no plug fouling)

Originally posted by leif:

I also have done the mod. But it is still abit cold and muddy here in Minnesota for me to get out and try it. I didn't change any jets yet. If I do, will I need to change the air jets too? Do they get changed hand in hand with the gas jets?

I have not heard of anyone changing the airjet? i would think that you are going to need to richen up the main at least, since you basically cut massive fuel to the engine by cutting back on the spray...since it used to spray for 3-4 seconds, and rarely do you hold it wide open for more than that, the spray was richening the top end. you need to increase the main jet to compensate for this or you probably will run lean and flat on top. I tried the 165 and it was a bit lean...the stock 162 was WAY lean on top. With the 168 it pulls long and hard...

Thanks. I'll given it a try.

therapture & Boomer

Here is all the stats on my bike



*Needle-----------Center Slot (Stock)

*Pilot Screw------1 3/4

*Squirt Duration--.3 Sec. (Approx)

*Stock Exhaust (With Custom Self Built Screen Cone For Spark Arresting)

I took my bike out this last sunday for its first test ride after the BK mod. The weather was the standard Oregon 48 deg. with clouds and some rain.

While the bike rips every where from the lower mid to upper R.P.M. range (with no signs of weakness)


I still have a slight bog at the bottom :D I guess it's now time to make some other adjustments to the carb.

What I need to know is... Do you think that this bog is caused from a lack of fuel, or a lack of air? Do I need to make some slight adjustments to the BK mod screw? Pilot screw setting? Needle clip?

All I'm looking for is a bike that will loft the front wheel up & over stumps, roots, mud holes, rocks and other kinds of trail debris that creep up on me and want to grab the front wheel and "slam dance" me & my bike to the ground. :D

Thanks for all your help :D


It sounds like you may need to work with the delay screw to get rid of that bog. Some have had luck with 1/4 to 1/2 turn in either direction. I'm guessing that as the squirt duration is reduced, the actual timing of the squirt in relation to the slide becomes even more critical. The delay screw adjusts this component.

Good luck,

Brian :)

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now