Carb slide spring mod

[damo1]

I was looking for something total un related amnd came a cross a number of threads about a carb spring mod.

So it goes something like this: Its for CV type carbs

Apparently you drill out your slide vacume hole ( not the needle hole ) one size above what ever the hole is currently, there was alot of talk about 1/8 being the size to go for.

This increases the vacume rate into the diaphram and lifts the slide faster.

To let the slide have less resistence you then remove the slide spring and cut off 1/2 a coil at time to let the
slide come up faster as well, but you can only go a maximum of around 2 full coils on the spring- about 1/4 of an inch in yank terms.

Apparently this was a dyno jet trick years ago or something like that??

Any way getting to the point , do you think this is a valid mod to CV carbs and would it really make that much difference to the performance of your bike other that a lighter throttle at hand?

Its appently supposed to help mid range preformance because the slides open faster than normal.

Cheers damo

[Yella]

I have done this. Seems to work makes the slide rise quicker giving better throttle responce. Alot of the jet kits come with the drill and the springs to do it.

[NINJAINOZ]

Im hoping to find a Dynojet kit soon, As Yella mentioned they come with the correct size drill bit for each model which hopefully should be tested etc to work correctly

All the Dynojet kits have PDF's available, This is the kit I need>
http://www.dynojet.com/pdf/2154.pdf

Factory Pro kit>
http://www.factorypro.com/Prod_Pages/prodk77.html

[ozzy1100]

dont forget to look at the factory pro stuff as well...
I always like it better

[Gix11]

Yea, what Ozzy said. Factory Pro worked out better for me and a few mates.

[ozzy1100]

also a trap for yng players dyna fet kits have their own numbering on jet size
ome and factory pro use the same system of the numbers are drill size ie 150 is 1.5 mm
dyna jet kits are diff and from mem use a flow size but I could be wrong has been about 6yrs from the last time I did any
jet work. there used to be a very useful convertion table somewhere on the net.
nothing worse than sorting though a box of jets ......

[hooligan]

i looked at doing that on my ktm as there's a lot of forum talk about drilling the bst40 carb that comes on the ktm 640's, i ended up just buying a flatslide.

[NINJAINOZ]

I will buy either kit if they pop up cheap to give them a go, Would not bother most people but The Factory Pro site has no PDF/instructions & does not give much info on what is actually in the kits (jets sizes etc) but I spose you are buying that info too!
The Factory Pro kits I found (for my bike) say you dont need to drill the slides so I'm guessing they supply much lighter slide springs?

http://www.factorypro.com/Prod_Pages/prodk77.html

Lots of good info in the Factory Pro site but fuck their website is all over the place, I managed to find this though which may help some people>
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

[ozzy1100]

their pink sheet that comes with the kit- read it then read it again after that read some more put it down come back later and repeat..........
from my exp if it do not come in the factory pro kit then you dont need it, all their kits are suited to the use for the stage of kit and bike.
from mem there is a big diff also in the needles between the two brands

[NINJAINOZ]

Yeah I was going to mention the needles would have to be different to allow for the different slide progression with the Dynojet kit drilling the slides & Factory Pro being not drilled, Either kit would have to get a noticable gain if done correctly, Factory Pro would be quicker & easier too & if you guys recommend them I might go that way rather than Dynojet
+ I like the fact that Factory Pro use OEM numbers on the jets, Thanks Ozzy

[ozzy1100]

I could be wrong my minds fucked from drink and herbs , so just check I could be talking out my ass.....

[NINJAINOZ]

I can read the pink bits dont worry, I will checkout the pink sheet when my new Factory Pro kit gets here from the USA, Found a (new/sealed) 1.1 kit with the titanium needles for $100US including postage, Hope it does not take long to get over here via priority mail?

[damo1]

I have done this. Seems to work makes the slide rise quicker giving better throttle responce. Alot of the jet kits come with the drill and the springs to do it.

Did you drill the slide?? if so what size did you go?

And how many coils did you end cutting off??

Did you do this before turboing or during the tuning process?

Chris - Do you know if it made a big difference for the guys talking about it on the KTMs??

And for the rest - cheers for the feed back on jet kits i know all that info was wanting to know about this mod
rather than the jet kit route.

Cheers damo

[hooligan]

A lot of the ktm forum guys said it did exactly what yella said, gave it more snap. when i was tossing up rebuilding the bst40 cv carb due to wear or buying a flatslide, i was emailing a guy who is a bst 40 KTM guru. He didn't recommend drilling as it would accelerate slide guide/emulsion tube/needle wear - on the KTM 640, the needle sits at a slight angle, my needle had almost worn through on one side and the tip was ready to fall into the motor. That's why i bought a flatslide, the flatslide only cost $100 more than the parts needed to rebuild the BST.
But if it's not an everyday ride, and you just looking for a bit more snap, i say do it.

[Hillsy]

I can read the pink bits dont worry, I will checkout the pink sheet when my new Factory Pro kit gets here from the USA, Found a (new/sealed) 1.1 kit with the titanium needles for $100US including postage, Hope it does not take long to get over here via priority mail?

Mate - not sure if this is going to be an issue with your ZXR carbs, but there's been instances where titanium needles can saw away at the stock needle seats at an alarming rate. Happens on YZF750/1000's a lot and other horizontal carb'd bikes would be the same. Some of the Keihins have pressed in (IE: not replaceable) needle seats which means these needles can FUBAR your carbs. At the very least, check if your sets / emulsion tubes are replaceable ones (I know the YZF ones are, but the later ZX9's aren't).

Just a heads up and worth checking out before you put them in, I reckon.

[Yella]

Did you drill the slide?? if so what size did you go?

And how many coils did you end cutting off??

Did you do this before turboing or during the tuning process?

Chris - Do you know if it made a big difference for the guys talking about it on the KTMs??

And for the rest - cheers for the feed back on jet kits i know all that info was wanting to know about this mod
rather than the jet kit route.

Cheers damo

Its no good withthe turbo best off running them stock just rejetted.
From memory it was cutting off 3 coils but not sure on the drill size but wasn't much

[NINJAINOZ]

I will have to see what Factory Pro say, They have their patented High Dispersal Jets that are actually listed to suit the (Non-replaceable) ZX7 emulsion tubes which should be the same I would imagine, Should be half way down this page>

http://www.factorypro.com/products/Jets, Keihin, buy.htm

[Hillsy]

Says they're not available for ZX9 00-01 only, so you should be OK.

But, if you're just getting titanium needles to run on stock needle jets, that could be trouble.

[NINJAINOZ]

Going over the details with Factory Pro, Waiting to hear back about the needles/emulsion tubes etc, Basically I did not receive an answer in the first reply about the titanium needles & mentioned they dont have a set of these carby's so they did not know about the emulsion tubes in my CVK's? Thought they would know this stuff anyway

The jet holders run on a different angle to where the needles sit, Looks like they would be pressed in & hopefully out?
I got a pic of my spare CVK's & you can see the tube where the needles sit, I could try getting a run up & hit it with a hammer & see if it moves?>
http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/ZXR750CVK_zpsba151aff.jpg

[Hillsy]

They look look exactly like the E model zx9r ones to me - which are pressed in and not designed to be replaced.

[NINJAINOZ]

I managed to get one of the tubes & needle jet out of my spare carbs, I gently tapped it out with the hammer, I did not need a run up!!!
It is hard to see if they are actually worn or not? Maybe they are worn that far there is basically no lip now?

The fuel needs to get into the tube somewhere to be squirted out the needle jet so the tube is 2 pieces, I just tapped the lower tube which pushed the needle jet out, I dont know why they say these cant be replaced & why the parts diagrams dont even list these parts? It is a part that wears & it CAN be replaced???
http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/ZXR750NEEDLEJET_zps72c4e5fd.jpg

http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/ZXR750NEEDLEJETSIDE_zpsbce2adc9.jpg

I was pretty certain the later ZX7 or possibly ZX9 needle jets would fit & Marc from Factory Pro has confirmed it with this link>

http://www.factorypro.com/Prod_Pages/prodk51.html

The Factory Pro patented High Dispersant Jets that are listed to suit the later ZX7 / ZX9 are the same dimensions, They may aswell be $1000000 at the moment cause I cant afford $320US for a set of 4
I will be glad when I buy a set of FCR's one dayI think!
http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/ZXR750NEEDLEJET_zps815bbd15.jpg

http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/needle_jetKawzx90000-01HDJtopdown_zpsed2f3b78.jpg

Sorry for the slightly off topic thread hijack Damo1 but it is another part of the CVK carby & there does not seem to be any info around at all showing the pics & dimensions etc of the Needle jets so this will hopefully help others out there (& myself when I forget & need to come back to this thread)

[NINJAINOZ]

I received the Factory Pro kit the other day & got it all sorted, Went to leaner main jets, 170/190 down from 180/200, Runs way better now, I might still sort out some needle jets later on though if I can find someone that could make them for a reasonable price?

Thanks for the advice guys, The Factory Pro kit worked well

EDIT: not Jet needles, needle jets

[Redmohawk]

I received the Factory Pro kit the other day & got it all sorted, Went to leaner main jets, 170/190 down from 180/200, Runs way better now, I might still sort out some jet needles later on though if I can find someone that could make them for a reasonable price?

Thanks for the advice guys, The Factory Pro kit worked well

Make you a set of Needles , I'm not to sure there are many people mad enough to try that sort of hat on.

[NINJAINOZ]

Pretty fine machine would be needed to cut a set of these needle jets, You can see the measurements posted above 6.6mm & 6.8mm + all the other measurements would need to be spot on too, & 4 times over all the same, Would be a fiddly job, Would be nice to have a CNC type machine to do the job

I could send one or 2 of the needles to double check all the measurements

How would you do these Red?

[Redmohawk]

Would something like this do the trick with a file ?

3857

I've made a few in the past on a cheap china lathe, this was a emergency "quicky" made out of some brass allthread.

3858

[NINJAINOZ]

mmmmm precision looking gear there in the first pic, Was going to mention joking around I could possibly have a go with a drill & file like that but I think I would like them made with something a bit more accurate

The needle you made looks pretty good, I bet it took some time checking the measurements as you went along, Would only have to bump the lathe & the needle would be cut in half

I need the needle jets (not needles) made which would also require some spot on measurements on the inside also
http://i1250.photobucket.com/albums/hh540/NINJAINOZ/ZXR750 FIGHTER BUILD/ZXR750NEEDLEJET_zps815bbd15.jpg

[Redmohawk]

I only have my old lathe here atm (really need to rebuild the tool carrage, is a little sloppy). I assume brass is what you want em made out of ? Draw up what your after and I'll see what I can do.

[NINJAINOZ]

I dont have any vernier calipers only a micrometer which wont be able to get all the measurements, The 3 main measurements are shown above, I could just send one of the needle jets for you to copy, The hole where the needle goes would have to be smaller than the worn out ones I have though & exactly what size I am unsure? Finding a brand new-ish set of carby's with needle jets with absolutely no wear would be hard to find, Would just have to sort of guess really & estimate what size they would be before 20 years of wear?

You reckon an old lathe (with a sloppy tool carriage) would be up to it? Anything is possible if you take your time I spose
What sort of dollars would we be looking at to do 4 needle jets? & yeah they are brass

[Redmohawk]

Send me one and I'll see what I can do , I have another lathe just out at the farm (only 20 min away) But I'm dragging it over to my place in town soon (prob two weeks) . Cost you a beer when we meet up on a ASF ride one day.

[NINJAINOZ]

Looking at the needle you made im sure you could cut a few of these needle jets, Might take a bit longer than just programming a computer & letting it cut them but hopefully you can get them close enough

We would have to go over the internal dimensions when the time comes, Maybe leave the hole for the needle a bit smaller & I can take them out to where they need to be when I work that bit out?

We will work something out, Would be worth more than a beer

[NINJAINOZ]

I got one of the needle jets on the way to you yesterday Red, Let me know when you get it
Thanks

[Redmohawk]

Noooo prob