BK Mod for the 98/99 exists!! It is called the KL Mod!!

thanks for the PM kev. the man was deranged.

your mod looks excellent. i would have chopped the rod in two, pulled 3mm out and then with absolutely no expense spared in time honoured Taff Lloyd tradition; used a block connector.

yes i know, this would have made the mod way beyond the means of most mortals but success and money are easy bed fellows.

keep it up, looks good. OBTW if i can't get mine to run very well i'll try it as well.



run this by me will you?

the rod is shortened so that it doesn't push the pump. so the sprung arm holding the rod is holding the rod away from the base-by 3mm. right?

if the rod is (later on) depressing the pump if you come back from say 1/2 to 1/4 throttle how does it now squirt the same amount of time as from the closed throttle?

ABTW i lost my little rubber boot and the rod yesterday. wouldn't you just believe it! i'll make the rod next time out of SS.

anyone measure the dimensions of the 'L' rod?


[ December 03, 2001: Message edited by: Taffy ]

I am going to try this mod out on my DRZ400. I'm still deciding which approach to try... the KL mod approach or the Taffy block connector approach. What pro/cons is there between them? The only thing I can see is:

--the TaffyBlock (TB) sounds easier to do

--TB would have built-in adjustability

--but you would not be able to fit the rubber boot over the block connector?

Lastly, what is the answer to Taffys last question? Will either mod (KL or TB) adversely affect pump function from 1/4 throttle? As far as I can imagine, it should not present a problem... any more than the origional BK mod. :)

[ December 08, 2001: Message edited by: ballistic ]


i've only tried this in the garage during the week but what i did was make a rod up and made it the right length that the squirt only happened after the slide was open. i have two choices now;

1) (std)full pump stroke which means that whenever i touch throttle i will get a little squirt to give it a jolt.

the bad news; fuel economy will go through the floor, back to squirting fuel in long after i need it.

2) put block connector at base of rod to shorten stroke. this gives just a short "blip" of fuel at closed throttle.

bad news; no APJ at all at anything off of a closed throttle. that's right! there is no APJ after you first touch it! so if i'm doing 15mph and i see a bolder infront i can't "snap" and "pop" the front wheel over with a "jolt".

i suppose a little snap off of a closed throttle is better than nothing and to be honest the jetting on mine is very good higher. but it isn't the wheel popping type stuff.

i've definately got the better deal.

now as far as the block connector goes, well you haven't looked at one closely before! you get the smallest one that will take a rod through the middle. then using a stanley knife you peel off the plastic body. next you tighten the rod in via the two screws. check how proud they sit which is usually verey very proud.

then grind a little off the screw threads and then upon tightening the heads the screws are only just proud.

now you have infinite adjustment and it all tucks under the rubber gaitor. simple!

by the way. i used a coathanger for the rod :D:)


[ December 09, 2001: Message edited by: Taffy ]

just got in from testing.

first-third test

rod chopped in half and 2mm removed. tried all kinds of delayed start and in the end decided that i liked it to be there immediately. the way to tell is to look at the drilled hole in the black rocker arm. this is actually OVAL shapped and the rod was best at the top, in other words at it's full length.

now with a new full length piece of coathanger and the use of the same block connector i slid it down the rod to just above the entrance to the APJ housing.

fourth-sixth test

the actual stroke is about 3mm to look at. by lowering the block connector bit by bit i stopped at 1mm of travel and that was fine.

this gave me snap from closed in first and second. in third i wouldn't expect to go back to a closed throttle.

it may come down even more. to say .75mm or so.

as i've said above there is no APJ at higher revs so this is for first and second gear snap.

the bike was generally misbehaving at closed to 4/5 yards i think due to the EKP needle i'd put in.

if i were to improve it i would drill down vertically through the oval hole and screw a 2mm screw in. the friction of the plastic would stop it falling out. this could be adjusted to be touching the rod (ready for instant squirt) or delayed as the plastic rocker arm moves down and at first takes up the slack.

to get really technical you would thread to bottom of the rod and put two nuts on it for finite adjustment.

the block connector can't even be valued it's so pitifully cheap. i pulled one screw out and cut it down and put the other in the box. HAVE NO DOUBT THAT THIS MOD WILL FIT UNDER THE RUBBER BOOT.

in britian we have a saying " a good engineer is a man who can do something for a shilling that someone else would do for a crown".


[ December 10, 2001: Message edited by: Taffy ]


i hear there's an old buriel site in Northwood. it's for a tribe called the fakawee. have you heard this ancient story??

warning; this is tinderbox dry.


As in "Where (we're) the Fakawee?! :)


do you like it mate?

i wish i'd looked before. but it's important to understand that my jetting had to be done with no APJ.

it's only when it's done i know what i need and it's that tiny blip of the stuff. if BK hadn't come along i would have zero'd in on this in exactly the same way.

i hate to piss you off but i spent an hour looking at it, went in the house, found an old coathanger and fitted it in ten minutes. rode it for an hour yesterday.

i didn't find any disadvantage to it squirting IMMEDIATELY although to be fair it didn't actually hit the slide plate.

i'm going to 150MJ, 160MAJ, EMMc5 needle, PAJ55, PJ35 (down 3), 1.5 turns PS. .75-1mm rod movement. i've got another ride coming up this weekend. :):D


thanks all for replys. Gotta wait till this non-stop rain lets up to try it out.

I did the mod on my '99 today and it works great so far. (I've only done the run up and down the street test.) I didn't have to shorten the rod because the stream didn't hit the slide at all. Before the change, the squirt length was more than 4 seconds! Now, it's less than a second long and the throttle response seems much crisper. We'll see what it's like tomorrow when I'm out riding. Hopefully better gas mileage will be an added bonus. Thanks, Kevin, for the good idea!

My pleasure Rich! Someone wanted references from me as to where I got this idea. JD gave it to me, I just tailored it to our 98/99's.

This is a bastardized BK mod, but IT WORKS!! :)

I just got back from riding and I'm happy to say the KL mod is a total success! The bogging has gone away and throttle response is much crisper and snappier. :)

rode with just .032" (.8mm)of pump rod action yesterday and the bike was even better.

i'd say it was great but it doesn't start first time anymore if i'm piddling about at low speed on and off the throttle.

i know that i'd like to turn it in even more but i don't think the pump action can work efficiently at such a short opening.

if just gently winding on the throttle in second the bike is **** , awful. please take away the APJ altogether.

i've come to the conclusion that for green laning NO APJ is desirable.

if i still own the bike i will try it down at .024" (.6mm)stroke action.



Great job on developing this mod! I think some 98/99'ers will benefit graetly from this.



Hey guys,

I am assuming this mod also works on a 01' and 02' KTM520 right? I have done the BK mod about 5 times on 426's but havent done the mod for the 1st gen FCR carbs yet. I just looked at my friends 520 last night and he is really interested in doing this mod in the next 1-2 wks! Does anyone have pics yet (come on guys it is easy to snap a few pics...and then email me them and I will post em')? If so please send them to me via motoman393@hotmail.com if no one has any pics, I guess I will take them and post them on my site in the next few weeks! I would like to get a "visual" pic in my mind before I go drilling into my friends carb (if it where my bike I wouldnt worry about it, but you know how it is) Thanks a bunch,


I FINALLY got my Daughter's Barbie Doll software w/ Digital Camera (total cost ~$25.00 - meaning top notch quality) loaded into my PC. Maybe now I can start to flood the 'net w/ pics!! :)

I got a p38 for 98,99 yz /wr for $40 send me a e-mail I did the bk mod and don't need it anymore

I wanted to add an interesting bit that "BK" mentioned on the YZ forum about the P-38 and alternative ways to reduce pump flow on the 98/99 models-



I'm not sure wat you are refering to with P-38. You can limit the spray with the old style carbs by adding a little stopper to the lower side of the diaphragm. I used to use a small hollow piece of aluminum tubing that would press on to the little nub of the diaphragm and then shorten it to length on a sander or with a file. It takes a lot of trial and error to get it right but its worth a try. I think adding 2mm might be close. Give it a try and let me know how it works for you.


Another option to consider,


so what could be cheaper, what could be easier to do and what could be easier to adjust than the mod i did?

all i can imagine that could make my mod any better is to have a nut thread on the rod.

i'm even adjusting the thing down to the nearest thou for chrissakes!!!!!

it's off the shelf, valued at about 5p (8 cents)and takes about 10 minutes to do from end to end. when it's done you can adjust it in about 4 minutes (as long as the exhaust is cold).

it shouldn't come down to me saying "it's better" but i might as well if nobody else can see that this mod kicks 'others' into touch. no offense kev.

put it this way, if i'd thought of this first, would anyone drill the base plate or unbolting it to put in a tiny piece of metal that couldn't be gripped again to be ground out even smaller?

i've measured the pump at over 3mm (.120") and turned it down to 1mm (.040") then .75mm (.32") and finally .6mm (.024").

so how would i have modified this little tube down from 2mm up to 2.25mm and then 2.5mm?

petrol pissing everywhere, and no finite control. great idea!!!



You have a great suggestion in your pump adjustment. Didn't mean to overlook it, just another simple option.

"petrol pissing everywhere,..." Nice description. :)

Always good for a chuckle. Happy New Year!


[ January 01, 2002: Message edited by: James Dean ]

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