Alrighty, I think it's time to copy another DIY over :thumbup:

Drilling the bottom of the slides on these carburetors makes the needles respond faster. In the low to mid range of the RPM band it'll make the carburetors a little more responsive. This in no way is a way of 'gaining horsepower', but is more 'fine tuning'. I therefore don't recommend doing this unless you've already torn into the carb's a couple of times and are looking to get your carburetors tuned to their maximum ability.

I'll also note that you should be very careful when you're dealing with the slides as the diaphram will tear if you're not careful and they are around $100 each!

Alrighty. First (and I'm NOT going to get into it as you should already know how to do this if you're going to be drilling your slides) remove the seat and gas tank. While you don't have to remove the fairings it does make it a little easier to get the tank off.

Remove the gas tank and tackle the carburetors one at a time:
http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=153
To avoid stripping the screw heads, I recommend an angle screwdriver head with a #2 phillips head.

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=152
Pull the cap and...

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=155
Remove the spring.

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=154
I left the needle in and pulled the slide in a single step. I prefer to stick a finger IN the slide and gently pulling the slide/diaphram out. Do this slowly and when at all possible avoid contact with the diaphram.

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=158
Again when you are dealing with the slide avoid touching the diaphram. Once out you can tip the slide upside down to remove the needle (and any washers that are in there).

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=157
Here's a picture of a #70 drill bit. It's tiiiiiny. You can find them on eBay SHIPPED For like $2.50 . This would be the second one. After I took everything apart the original drill bit was no where to be found. So I literally had to put everything back together and order another one

... 5 days later:

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=159
Here's the bottom of one of the slides. Notice that the hole (not the one in the middle) isn't directly between the center hole and the outside of the tube? When you drill the additional hole (I did it opposite the original hole) try to do the same as the center part of the slide is kind of large and if you drill directly between the outside of the slide and the center you'll not make it through .

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=156
Viola! So again the hole isn't prefectly in between the center of the slide and the outside. Make sure to gently blow off any plastic cuttings from around the slide. Once you're set put everything back together

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=150
As has been suggested a little vaseline or light grease around the machined groove will help seat the diaphram. You can see in two pictures up a bit of grease on my diaphram from this :) . Pay special attention upon reassembly to make sure the diaphram is fully seated in the machine groove for it. It'd be a shame to go through the effort only to tear the diaphram when you put the cap back on

The idle was crappy after I got the bike back together and started it. I was kicking myself and planning on having to tear the bike BACK down Then I rechecked all the hoses and noticed one of the vacuum lines pulled out . Upon reconnecting everything was kosher.

After a quick warm-up and jot around the throttle is a bit more responsive below 7,000 RPM or so. I'd say it was worth it (probably worth doing if you're already there fine tuning needle height). The biggest noticable difference is when I'd blip the throttle on downshifting. Sometimes the throttle was sloppy when I blipped it, but now it seems more instantaneous. Me likeys!

BTW: If you do tear one of the diaphrams, talk to TheDuck :p He has a pretty effective way of patching the diaphram with a rubber tire patch that sounds to work.

lol... I was wondering when this one would show up. :p That drill bit looks awfully familiar. :D

Whatever you do, don't post up a cush drive DIY or Richard will go bonkers. :fightmallets:

I shimmed the needles with 2 #4 washers per needle and tore the snorkel out of the bike. It made a huge difference to the responsiveness. Have you done this as well as drill the slides out?

:laugh: I'm surprised he got steamed on that one. I think perhaps he was more leaning towards the people going a bit over the top on such things. ie. putting a solid cush drive in. Now THAT is foolish to me.

I shimmed the needles with 2 #4 washers per needle and tore the snorkel out of the bike. It made a huge difference to the responsiveness. Have you done this as well as drill the slides out?

Yes. Well yes and no :lol: . Drilling your slides and shimming your needles does two different things. Shimming the needles affects the amount of fuel that enriches the mid-RPM power band. drilling the slides affects how quickly they move. So I have Factory Pro needles that are adjusted (same thing as shimming needles) and the slides drilled.

Kawasaki was pretty close when designing the total size of the opening to the slides so it's a very small hole I drilled. TheDuck tried a larger bit (I believe it was a #50) and the engine bogged as the needles moved TOO quickly and suddenly the bike was too rich. He then epoxied the holes and stepped down to a #70 and the result was spot on. I've tried the #70 and got the 'desired result' and am content as well ;)

Well, maybe I'll try it out on the 250r with washer shimmed needles. Let people know how it goes.

That is if I can convince my fiance to let me take it all apart again. she was really apprehensive about letting me rip into it the first time.

Greg- if you're going to tear into the 250 "one last time", consider taking the mixture screw plugs out so you can tune the idle circuit as well.

Drilled my slides tonight. Not much to add to Vex's DIY except I used a pin vise with the #70 drill bit. To give you an idea of exactly how small a hole we are drilling, here's a picture of the bit in comparison to the Ninja key. :)

http://lh6.ggpht.com/_geC920GCq38/SZkfcCjUu9I/AAAAAAAACwc/LI_p4EJfWDA/s640/DSC05122-1.JPG

Thanks, TJ. Can't wait to try it out. Hope it runs. :p

Got my #70 (.028) bit from local Grainger($1.60). Home depot&lowes wasted my time. I lost it in the packaging for a second:eek: Somehow it fit in my B&D drill chuck. Still working other stuff...so I haven't tested it yet.

Awesome write-up

if anyone is interested in doing this mod and is having a hard time getting a #70 bit, PM me and I'll be happy to send you the one I used for free. I got the one I used from Vex as I could not find any on island and shipping to Hawaii was more than the bit was worth through a vendor. Throwing it in an envelope and mailing it somewhere costs the price of a stamp. :)

kkim, notice any difference with this mod?

I'm ashamed to say I've not ridden the bike yet since doing this. :o

I shimmed the needles with 2 #4 washers per needle and tore the snorkel out of the bike. It made a huge difference to the responsiveness. Have you done this as well as drill the slides out?

What's a snorkel????

http://www.ninjette.org/forums/showthread.php?t=10090

http://www.ninjette.org/forums/showthread.php?t=5586

just curious how deep do you drill the hole? The slide looks like a solid piece to me, but maybe I am mistaken. Do you just drill until it goes through the other side? I have never pulled the slide out.

thanks

yes, all the way through like the hole that's already in there, only on the opposite side of the slide.

http://www.ninjette.org/forums/picture.php?albumid=23&pictureid=156

the larger, towards the bottom, is the present hole, the smaller, at the top, is the one you drill. the largest one, in the middle, is the hole that the needle slides through.

As Vex said, be very careful of the hole placement. Look from the inside of the slide to clear the slide "wall". basically, put the center of the new hole the same distance from the side of the slide that the center of the present hole is.

If you've never done any jetting to your bike, I don't know if this is such a good first jetting mod. This is like a fine tuning after all the major jetting stuff has been done.

I jetted my bike, but never pulled out the slide so I didnt know if you drill "through" the slide , or just "into" the slide. If that makes sense.

Thanks for the info. Im jetted and have the area p, so im sure drilling the slide will also help the motor run smoother.

cool... I'm sure it will help. I've not ridden mine yet since drilling the slides, but plan to later this morning.

Got to ride the bike on the street today. It does seem a lot smoother when downshifting and blipping the throttle. The response is improved and very "instantaneous" feeling.

Haven't ripped through the gears in the mountains yet, but I'm sure the throttle response will be great for entering corners and blipping the throttle when downshifting.

I didn't know what to expect and how this mod would really affect the bike, but I've got to say... I like it! :D

Thanks for the bit, TJ! :thumbup:

nice...i've bought an extra 08 carb and it's been sitting there for the last 4 months or so..bought it to do this mod just in case I mess up :) i'll find the time to do this sometimes...the women has been keeping me busy :)

nice...i've bought an extra 08 carb and it's been sitting there for the last 4 months or so..bought it to do this mod just in case I mess up :) i'll find the time to do this sometimes...the women has been keeping me busy :)

The a set out on EBAY...I was thinking the same thing. Buy them to make the mod on and have a spare set just in came things get FUBAR. :thumbup:

bumping this one back up for info.

so just verifying... if all i have done is the shimming, removing my snorkel, and switching to a drop-in k&n filter, i should NOT do this mod yet?

only if i have changed the jets? what would happen if i did this mod without jetting? thanks.

you could actually do this mod at anytime, as it is really to fine tune the the throttle response/revability of the bike. It is letting more air pass quickly so the slides can move up and down with less restriction from the diaphragm.

Do you find the throttle too slow for you as far as coming back down after you close it?

no i don't notice the throttle being too slow. then again, i have no other bike to compare it to.

i am just a sucker for cheap, effective mods.

while it does make a slight difference in throttle response, the risks far outweigh the benefits if you are just doing it for the sake of doing it. remember, you'll be playing with those $100 slides and the chances of tearing them is much greater as you'll have to remove them from the bike to work on them.

my main interest in this was due to the fact that I "blip" the throttle on all of my downshifts and most of my upshifts, too, so timing the shift has become easier with the quicker response of the carbs.

hmm... one of those "if it ain't broke..." things, eh?

i guess i can pass on this one then. i don't know if my throttle is slow or not. seems fine to me. i don't even know how to blip the throttle when downshifting. tried with both my cars and this bike. can't get the hang of it.

anyways, thanks.

if anyone is interested in doing this mod and is having a hard time getting a #70 bit, PM me and I'll be happy to send you the one I used for free. I got the one I used from Vex as I could not find any on island and shipping to Hawaii was more than the bit was worth through a vendor. Throwing it in an envelope and mailing it somewhere costs the price of a stamp. :)
Still have that drill bit K?

sure do. you braving opening up the carbs now? :thumbup:

sure do. you braving opening up the carbs now? :thumbup:

hummm....After adding the white stripes to VoodooMaster I have decided that I like her and might keep her on hand. I think it is time to dig into the fuel line. I can't stand the on-again, off-again start problems that I have experiences, so I am going to add the washers, and then tweek the idle mixture screws. I bought a set of carbs from EBAY and dismantled them last week. They cane apart easily enough. The slides and the jets are straight forward and the lead plug came out from the mixture screws without toooo much effort. I finally got in one of those offset screw drivers from Milwaukee, so I think I have almost everything I need. If you happen to have 4 of the CORRECT size washers for the jets in your pocket, I would be happy to let you give them to me!! The washers I have might be the right ones, but my mechaical skills are weak when it comes to telling a number 4 washer from a number 6 lug (:eek:).

The low end operation from idle seems to be crappy. When I twist the throttle a bit too fast she seems to bog a bit. Could be just me. Mid range seems fine for a 250. Operation past 7K is outstanding for a 250CC machine. It's the start-ability and low end operation that I just hate. I don't plan on adding a noisy exhaust, or bigger jets any time soon. Actually, never will mod the exhaust unless I can put an under-tail unit on her like the 600 has. Anyway, time to fix what I can on those two fuel mixing units..... fuel injection would have been the way to design this one.

Dave

lol... I recommend shimming as a cheap, easy, non invasive way to fix the lean condition of these bikes. You are about as invasive as you can get working on an entirely different set of carbs. I assume you're going to work on the purchased set and swap them in after you're done tinkering?

If so, get a jet kit at this point. I hesitate from recommending a jet kit due to the hassle of pulling the carbs. Since you have them out, it makes more sense for you to install a jet kit now and reap the maximum benefits of jetting. I have a Factory Pro kit, but Dyno Jet makes one, too. Either will do.

Even with the stock exhaust, you'll notice a big difference with a properly jetted bike.

while it does make a slight difference in throttle response, the risks far outweigh the benefits if you are just doing it for the sake of doing it. remember, you'll be playing with those $100 slides and the chances of tearing them is much greater as you'll have to remove them from the bike to work on them.

My 2 cents worth on this issue is I DO NOT think this mod is worth it for the above reason and there is nearly nothing to gain here. Yes there may be a SLIGHT advantage in response but in my opinion is not worth it.

lol... I recommend shimming as a cheap, easy, non invasive way to fix the lean condition of these bikes. You are about as invasive as you can get working on an entirely different set of carbs. I assume you're going to work on the purchased set and swap them in after you're done tinkering?

If so, get a jet kit at this point. I hesitate from recommending a jet kit due to the hassle of pulling the carbs. Since you have them out, it makes more sense for you to install a jet kit now and reap the maximum benefits of jetting. I have a Factory Pro kit, but Dyno Jet makes one, too. Either will do.

Even with the stock exhaust, you'll notice a big difference with a properly jetted bike.

HA! Sorry, my bad. No, those cheap carbs were from a 2005 model, and were only for me to fart around with...to figure out the degree of difficulty of disassembly. I won't be swapping those into my 2008 machine. :D

My 2 cents worth on this issue is I DO NOT think this mod is worth it for the above reason and there is nearly nothing to gain here. Yes there may be a SLIGHT advantage in response but in my opinion is not worth it.

Good input. What's your take on the needle shimming and idle screw adjustment process?

if you are thinking of going as far as drilling out the mixture screw caps, I think a jet kit is the way to go, other than the price of the jet kit.

once again Kkim is correct. If your pulling the carbs might as well put in the jet kit. If you have a full exhaust or are planning on getting one. Its a no brainer. You will feel a MAJOR horsepower improvement over just shimming the needles, at the cost of a few mpgs. In my opinion All these bikes need is a full exhaust (of your choice) and a jet kit. Just follow the jet kit instructions and you'll be rewarded.(Gearing is a option, and a cheap one at that.)

:lol: that little drill bit is really going to make its rounds I'm feeling :)

Did this mod today, along with switching out the stock needles for Dynojet ones. I figured why not, since I was already inside the carbs. It's a super easy mod, I must say, it only added like 5 minutes to the overall time and it seems to be pretty effective. Though most of what I'm feeling on the bike probably has to do with switching the needles and yanking the snorkel. This is still the best $1.77 I ever spent on a drill bit.
If an 18 year old with no previous motorcycle experience can do this right, anyone can ;)

Just a little tidbit, I found the bit at harbor freight in this mini set for $4.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=91682

ok question on the slides - when i did my needles i didn't tear, or pull or stretch the slides (or the diaphragm part) but I used my fingers to work the edges of the diaphragm up and off the edges of the carb, and when i put them back, they just seemed to sit there. didn't give any sort of tug or resistance (like glued in) when i tried to pick them back up and out (from pinky in the center "needle" hole) but didn't seem to be out of alignment on the edges, just right back to where they were. Also when handling the diaphragm i definately was putting my fingers all over the "mushroom top" or thin diaphragm part...will this inhibit or damage those parts? I'm a new bike and VERY new carb person...
also, the bike now doesnt have the same engine rhythm than before i did my needles (#3 notch, DynoJet kit with 2 washers, no snorkel, plugged kleen-air and two-bro slip on)...but i know that a needle mod also usually requires re-syncing the idle circuit and doing jets as well (#100 Keishin is my guess, wednesday maybe)

As long as you didn't rip or tear the diaphragms, you're fine.

You should sync the carbs if you're getting a rhythmic pulse.

also, I'd stay with the stock 98 mains for now until you determine you need to go richer.

she has balls out from 4-7K then 8-12 she really strains for power...so im thinkin the needles made the mid VERY rich and leaned out the top end...if I have half throttle she climbs a bit easier up top...still keep the 98 mains?

did you drill your slides?

nope, didnt drill slides. but been limited to half power for the past while because the throttle body was apparently set up in a manner to stop it prematurely in the wrong spot. *shrugs* we'll see what happens now...:-P

I'm planning on doing this tomorrow.... Has this mod (with #70 bit) NOT worked well for anyone?

Just drilled mine and got it all buttoned up a few moments ago.

Here's the thing.... the L diaphragm was torn at the lip in one spot when I removed the cover. AHHHHHH - PITA!!! :yell:
The L carb is tricky with all those little hoses routed over and around it.

I think this was from when I shimmed many months ago, but it is interesting that I didn't notice. I wonder if it was sealed just enough that it didn't matter (it was deformed slightly and sticking out the side. I didn't use the grease trick that first time I removed the covers, but you better believe I did today.

I'm so ticked.... I'm going to start her up and try a test run in a few minutes, before the rain comes.

^ Your suppose to pop them two vacuum lines off that side valve to make life easier :)

Here's the thing.... the L diaphragm was torn at the lip in one spot when I removed the cover.

Use tube repair glue and fix it!!!!

^ Your suppose to pop them two vacuum lines off that side valve to make life easier :)

:whathesaid:

^ Your suppose to pop them two vacuum lines off that side valve to make life easier :)

Yeah, next time.... one of them was a little stubborn, but now I know to work at it a little longer.

The test ride actually went well... throttle response is improved, and causes an illusion similar to what it felt like when I first shimmed. My midrange still sucks from yanking my snorkel 2 days ago.... I may put it back, but haven't decided.

For a while I have suspected my valves need to be done, because at my 7.5K they said they were barely within spec, and didn't change them. I am almost at 14K now, and the engine has sounded a little clicky, or chattery to me for a while. But now that I know the diaphragm has been torn at the lip, I wonder if it is more of a pulsation that I am hearing.... it is hard to say for sure.

Don't forget to resynch your carb
Posted via Mobile Device

Don't forget to resynch your carb
Posted via Mobile Device

Are you suggesting this because drilling may have thrown it off, or the potential for the leak in the L diaphragm?

I am about 1-2 months away from my next major service (14K mi), should be good waiting until then for the shop to do it?

Don't forget to resynch your carb
Posted via Mobile Device

And dont forget to put the spring seat in the correct way(the four leg thing that holds the needle in place). You know, so it doesnt block off the hole/new hole in the slide. < peeps with four washers might not have to worry :p

Everytime you mess with carb, it'll be out of synch so you'll need to resynch it for optimal perf.
Posted via Mobile Device

Everytime you mess with carb, it'll be out of synch so you'll need to resynch it for optimal perf.
Posted via Mobile Device

Gotcha - I didn't know just popping the top would do that...

Gehto style OK, or is it worth investing in the tool (this is my last non-FI bike)?

I didn't think about the plastic leg on the spring covering the hole :eek:

Just as an FYI, any Hobby shop that deals with Trains, Planes and R/C will have that drill bit in stock. If they don't, ask them if there is a Train, Plane or R/C event in town...

Just as an FYI, any Hobby shop that deals with Trains, Planes and R/C will have that drill bit in stock. If they don't, ask them if there is a Train, Plane or R/C event in town...

Yes, I found the local 'Hobby Town' had them.

Planning on doing this mod this summer to get my engine to rev a little quicker. The two bros slipons I installed also make my engine rev noticiably quicker. Would drilling this extra hole make my engine too quick to rev with my setup and start bogging?

(stock airbox, shimmed needles, idle mix adjusted, stock 105 jets)

Any more reviews on this mod? I am planning to do this on Friday but still giving it some thought, just got my AP exhaust, Pod filter, FactoryPro jetkit. Can't wait to get them in! :D

Any drawbacks to this mod?

I'd suggest doing this after you've done all the other mods and have a good feel/idea of what you have before doing this one.

Kelly, how was your results? Would you say its similar to a lighter weight flywheel for a car?

it makes the bike just "slightly" quicker revving. That may or may not be a good thing, depending on where you are and where you want your mods to go. It's more a fine tuning tool than a must have, IMHO.

I wouldn't (don't) do mods just cause some hack on the internet is doing them. I look at what I have and see if there are fixes for what I see is a deficiency or areas that need improvement. I normally do my mods in steps so I can compare and see if it leads to an improvement from what I just came from. if not, I usually remove it.

Alright looks like I'll have to wait and see, but you know..free mods are irresistible..

Instead of drilling a new smaller hole, could you just enlarge the existing air hole and get the same result?

yes you could. Thats what dynojet has you do with a drill bit that they supply. But from what I've read from people who use it, the hole is a touch too big some times?

yes, could drill the existing hole a bit larger, but if you go too big, repairing it becomes a problem. if you drill a small hole and it ends up being too big, fixing it is a simple task of gluing it back shut and redrilling another hole a bit smaller.

hopefully you won't have to as the size has been worked out for you in this DIY. :)

Wait an minute.... I did all my mods because the Great Guru kkim did them. ;) lol

In all seriousness though, a lot of us, self included, have probably done a lot of stuff because others did them first. It may not always be the wisest thing to do, but I have a hard time learning if I don't make mistakes along the way.

So I did this over the weekend. Took it for a short ride around the block and it was great. Today, I went for a longer ride to test it more. It worked great, but if I cruised at exactly 6k for about 10 seconds, the bike started choking like what happens when you need to switch over to the reserve tank, if i gave it full throttle, it took off like a bat outta heck like usual(I assume this is because the main jet is fully open at WOT). Took it apart to inspect. Diaphragms were both fine, and seated properly. Put it back together and took it for another ride. Same thing. Took it apart again, and glued the holes shut. Haven't tested that as the glue needed to dry, but I'm sure it'll be good as new. General note to pre-gen riders: this doesn't work perfectly with our bikes.

My question is, if I was running pods, would this still happen? the hole lets in air to let the slide move, so if there was more air, would it move to the right place immediately instead of going not far enough and starving the engine and then snapping to the right place? Anywho, I won't be trying to drill the slides anymore. It was a good experience since I learn best from doing, but I won't do it again

anyone know why this happened to me when I drilled my slides? My hole patching in my slides worked perfectly. I'm still wondering if I should try this again. I gave me problems when I only ran 1 washer on each needle, but now I have 2 on each. I'm mostly just curious why it didn't work, when the pregen and newgen slides/diaphragms are the same.

I have no idea. I haven't really been tracking the affects on pre-gen models, but I know there was a slight difference with their carbs.... IIRC, although many parts are interchangeable, the intake and/or exhaust side was bigger by a couple mm. But I have no idea if that is really contributing to your problem...... I would be happy that it is fixed with patched holes, and wouldn't worry too much since that is how it was originally designed to operate.

Guys - would you recommend drilling the slides when using a Dynojet Stage 2 Jetkit ...

This will be my racebike for next year. And i cannot take the snorkel or airbox off. I can use full system and an aftermarket air filter.

Guys - would you recommend drilling the slides when using a Dynojet Stage 2 Jetkit ...

This will be my racebike for next year. And i cannot take the snorkel or airbox off. I can use full system and an aftermarket air filter.

Hmmmm..... Not sure, you should check with the girls here.


j/k. I THINK you are supposed to drill for the DJ kits. I have a FP kit, which say you don't need to drill, but I did anyways (their recommendations seem a bit backwords to me, in more ways than one). What do you mean you CAN'T take off the snorkel or box? Do you mean you prefer not to?

The rules won't let him.

ya, AFM club racing rules at production will not allow modifying the airbox or its components :(

Here is the Dynojet kit link : http://www.dynojet.com/jetkits/motorcycle/kawasaki.aspx#250 ... The 2193 Stage2 kit for 08+ do not talk about drilling slides. The 2138 Stage3 kit for 07 and under does talk about drilling.


Are you saying you drilled the extra hole in the slide with the #70 bit? Am not referring to drilling the cap out, just to be sure we are on the same page :). I did not see your info in the jetting database, do you race/track the bike? How do you like your current setup. [I think we can discuss this in my other jetting thread]

I have a FP kit, which say you don't need to drill, but I did anyways (their recommendations seem a bit backwords to me, in more ways than one).

ya, AFM club racing rules at production will not allow modifying the airbox or its components :(

Here is the Dynojet kit link : http://www.dynojet.com/jetkits/motorcycle/kawasaki.aspx#250 ... The 2193 Stage2 kit for 08+ do not talk about drilling slides. The 2138 Stage3 kit for 07 and under does talk about drilling.


Are you saying you drilled the extra hole in the slide with the #70 bit? Am not referring to drilling the cap out, just to be sure we are on the same page :). I did not see your info in the jetting database, do you race/track the bike? How do you like your current setup. [I think we can discuss this in my other jetting thread]

Ahhh... that's funny, I thought Alex was joking about rules - I get it now.

Yes, I'm talking about drilling the slides themself (don't remember the bit#). My info isn't in the db, because I'm still dialing it in.... I was close, then swapped engines, so I had to start over. I'm close though.

I'd definitely check with your rules books on whether it's kosher or not to drill slides, but as they seem to allow tuning, I'd think it's allowable.

In theory, drilling the slides shouldn't affect your jetting much. It's more to increase the slide response speed, allowing more airflow between the two sides of the diaphragm. The #70 bit is correct for size. Also, if you fubar things or don't like it, you should be able to plug the hole with a little JB Weld or other permanent epoxy.

FWIW, I'm using the DJ Stage 2 kit on an airbox-less, Area P-full system bike, supplemented with a lot more main jets, replaced pilot (stepped up a size) and drilled slides. Love it

Modification of carbs (rejetting) is allowed. while superbike has no restrictions, i plan to race production class as well.

Since i need to keep the snorkel on, i have to check what will be best option (in terms of mainjet sizes). i can mess with the pilot circuitry later if need to.

Thanks for the info, what mainjet size (dynojet size) you are currently running?


I'd definitely check with your rules books on whether it's kosher or not to drill slides, but as they seem to allow tuning, I'd think it's allowable.

In theory, drilling the slides shouldn't affect your jetting much. It's more to increase the slide response speed, allowing more airflow between the two sides of the diaphragm. The #70 bit is correct for size. Also, if you fubar things or don't like it, you should be able to plug the hole with a little JB Weld or other permanent epoxy.

FWIW, I'm using the DJ Stage 2 kit on an airbox-less, Area P-full system bike, supplemented with a lot more main jets, replaced pilot (stepped up a size) and drilled slides. Love it

I just spoke with Dynojet ... They do not talk about drilling in their Stage2 Kit. However, as i understand this DIY is more of a fine tuning process, which can be done later.

Now, with the snorkel box ON, i need to figure out on the jetting.

got my #70 drillbits and will try this mod. gonna try 108 mains also

#70 drill bits really need to be used in a pin vise. i used a standard chuck and had to wrap duct tape around the the end for a shim. i have extra bits if any one needs one.

went good. these bits are super tiny!make sure you carefully judge hole location.if too close/inside you will hit springholder boss on the other side. i had to use max speed to get bit to cut. one thing i like about secondary hole is if doesn't work ya can plug it. nice!

^^ Yepp. It's worth the science, but I found response was better (smoother and less agressive, therefore a little easier to work with) in the mid range with the factory slides than with drilled holes. I plugged mine and had zero issues for many miles. It's worth the science though!

They have a habit of snapping up and down. Good for going wide open, not so great for street mid throttle, which was more my use. NBD.

Remember that those slides move up and down in response to vacuum as a method of controlling the airspeed through the throat. This is why they're called Constant Velocity carbs. There's definitely some tuning to be done with when and how fast those slides move for optimal constantness, but that takes some serious time :lol:

#70 drill bits really need to be used in a pin vise. i used a standard chuck and had to wrap duct tape around the the end for a shim. i have extra bits if any one needs one.

An old trick is to wrap solder around the shank of the bit in a neat layer.

good info the duct tape worked but barely