Anybody have a guide on whats involved in "re-jetting the carbs" on a 1992 ZX-6?

[92NinjaZX6]

Just wondering if anyone has a specific guide to installing recalibration jets for a 1992 Ninja ZX-6, im planning on putting on my Muzzy exhaust but i need to figure out whats involved to re-jet the carbs. I'm more of a fuel injection guy but ill give some fiddling with carbs a try if i can find some resourceful guide.

[StarGate]

Since bike size, carb model, exhaust system, other mods, all have an affect on what jets would make it perform best, you're not likely to find a guide that would give you the jet sizes and needle settings that would work for you. As for the actual work it's really pretty easy to do but not so easy to get it to run right. Pull the carbs, remove the float bowls, exchange the jets, remove the caps, adjust needle clip, reassemble and reinstall the carbs. Make any needed adjustments to the mixture screws. If you're not familiar with the carbs you can see a breakdown in the parts diagram at kawasaki.com under owner info. The trick with any rejet is getting the right combination of jets, needle height, and mixture adjustment for your bike. Here is a link that might help in trying to determine what jet changes you need to make.
CV Carb Tuning Procedures

[92NinjaZX6]

Ok, thats just too much crap to deal with, i guess ill just drop it off at a bike shop for them to do. What is considered fair labor for a job like this?

[StarGate]

To get it done right it's going to be costly. If you take it to someone to do for you try to get someone that is going to use a dyno and ega. There is a better chance of it being done right if they tune it on a dyno.

[StarGate]

P.S. If the bike runs good now and the only mod you are going to make is the exhaust change you probably don't need to rejet it but you might want to adjust the mixture a little.

[markbvt]

Be aware that whenever you make any change to the engine's intake or exhaust, you're going to end up with a different air/fuel mixture. In this case, the real question is, what sort of exhaust are you replacing with the Muzzy? If it's a similarly open exhaust, then you may not need to rejet. If it's the stock exhaust, you probably will -- but chances are you'll be fine just stepping up five points in main jet size (so, if the stock main jets are 120s, you'd go with 125s).

Quick primer: most modern CV carbs have two replaceable jets (main and pilot), a needle, and a pilot screw (aka the mixture screw). The pilot jet and pilot screw control the fuel/air mixture from idle up to about 1/8-1/4 throttle; the needle takes over from about 1/8 throttle to about 3/4 throttle; and the main jet takes over from 3/4 to wide-open throttle (this is a rough guide -- the ranges actually overlap a fair amount).

Typically, one starts the rejet procedure with the main jets. Install your new pipe and see how the bike runs without rejetting; chances are it'll be lean (go for a short ride, run it through the rev range, see how it feels, make a mental note of where any hesitation or rough running occurs, and when you get back home pull a spark plug or two and see what color it is -- white/grey = lean, tan/brown = good, black = rich, generally speaking). If it turns out the bike's running great and the spark plugs aren't indicating a lean condition, then great, you're done.

But my guess is you'll need to rejet, so pull the carbs, remove the bowls (don't forget to drain them first), remove the main jets, and install the new jets. Reinstall float bowls, reinstall carbs on the bike. Find the first carb's pilot screw (a maintenance guide for your bike would help, or just find a diagram of your carb model online) and gently screw it in until it stops, counting the number of turns, then back it out again to where it was and back it out another turn or so. Do the same with the other carbs. This will richen up the idle mixture.

Start up the bike and take it for another test ride. See if it performs notably better than it did without the rejet -- you may need to experiment a little with the main jet size. Also note where it feels strong and where it feels like it could be better. You may need to pull the caps off the tops of the carbs, remove the needles, and shim them (it's unlikely that your carbs have needles with moveable clips). Needle shims are just tiny washers that raise the needle slightly, thereby richening the mid-range mixture. Try a single shim on each needle first, and if that doesn't feel like enough improvement, you can always add more.

Work methodically, keep track of what you've done and what the results are, and don't be afraid to experiment a little. Rejetting carbs is not difficult, it just requires a little patience and trial-and-error. In my opinion, you'd be best off doing this yourself, not taking the bike to a shop. Unless you have a shop around that specializes in carb tuning (and these seem to be increasingly rare), it probably won't be done ideally anyway.

Oh, by the way -- contact the manufacturer of the exhaust and ask if they have jetting recommendations for their exhaust on your bike model. Chances are they do.

--mark

[92NinjaZX6]

Originally Posted by markbvt

Be aware that whenever you make any change to the engine's intake or exhaust, you're going to end up with a different air/fuel mixture. In this case, the real question is, what sort of exhaust are you replacing with the Muzzy? If it's a similarly open exhaust, then you may not need to rejet. If it's the stock exhaust, you probably will -- but chances are you'll be fine just stepping up five points in main jet size (so, if the stock main jets are 120s, you'd go with 125s).

Quick primer: most modern CV carbs have two replaceable jets (main and pilot), a needle, and a pilot screw (aka the mixture screw). The pilot jet and pilot screw control the fuel/air mixture from idle up to about 1/8-1/4 throttle; the needle takes over from about 1/8 throttle to about 3/4 throttle; and the main jet takes over from 3/4 to wide-open throttle (this is a rough guide -- the ranges actually overlap a fair amount).

Typically, one starts the rejet procedure with the main jets. Install your new pipe and see how the bike runs without rejetting; chances are it'll be lean (go for a short ride, run it through the rev range, see how it feels, make a mental note of where any hesitation or rough running occurs, and when you get back home pull a spark plug or two and see what color it is -- white/grey = lean, tan/brown = good, black = rich, generally speaking). If it turns out the bike's running great and the spark plugs aren't indicating a lean condition, then great, you're done.

But my guess is you'll need to rejet, so pull the carbs, remove the bowls (don't forget to drain them first), remove the main jets, and install the new jets. Reinstall float bowls, reinstall carbs on the bike. Find the first carb's pilot screw (a maintenance guide for your bike would help, or just find a diagram of your carb model online) and gently screw it in until it stops, counting the number of turns, then back it out again to where it was and back it out another turn or so. Do the same with the other carbs. This will richen up the idle mixture.

Start up the bike and take it for another test ride. See if it performs notably better than it did without the rejet -- you may need to experiment a little with the main jet size. Also note where it feels strong and where it feels like it could be better. You may need to pull the caps off the tops of the carbs, remove the needles, and shim them (it's unlikely that your carbs have needles with moveable clips). Needle shims are just tiny washers that raise the needle slightly, thereby richening the mid-range mixture. Try a single shim on each needle first, and if that doesn't feel like enough improvement, you can always add more.

Work methodically, keep track of what you've done and what the results are, and don't be afraid to experiment a little. Rejetting carbs is not difficult, it just requires a little patience and trial-and-error. In my opinion, you'd be best off doing this yourself, not taking the bike to a shop. Unless you have a shop around that specializes in carb tuning (and these seem to be increasingly rare), it probably won't be done ideally anyway.

Oh, by the way -- contact the manufacturer of the exhaust and ask if they have jetting recommendations for their exhaust on your bike model. Chances are they do.

--mark

Its a Muzzy complete exhaust, it comes with the header, midpipe and rear muffler section, its not a slip on system. And i think my bike in the stock form is running rich, my spark plugs looked almost wet with gas and dark looking when i took them out to service them, so this might bring it to normal hehe. Will it harm my bike to ride it to the shop with a exhaust on before tuning?

[sullenfiend]

If its running lean it would run hotter, so i guess it depends on how far the shop is. I would suggest re-jetting yourself. I used the Dynojet Jet kit on my 95 600r and it was quite easy. I suggest you do the work yourself as mark suggested. You'll save some money for later mods and learn more about the carbs. Its much easier then it seems

[92NinjaZX6]

Originally Posted by sullenfiend

If its running lean it would run hotter, so i guess it depends on how far the shop is. I would suggest re-jetting yourself. I used the Dynojet Jet kit on my 95 600r and it was quite easy. I suggest you do the work yourself as mark suggested. You'll save some money for later mods and learn more about the carbs. Its much easier then it seems

I was thinking of riding it to "Advanced Kawasaki" up in Orange County, its about a 33 mile ride from my place. My bike doesnt run hot, in fact it runs too cold? The temp gauge sits at the first line at the bottom all the time, and i rarely hear the fan come on, unless i been sitting idling for more then 10mins. That place has a dyno-jet and do full tuning specifically for Kawasaki bikes (which reassures me they know the brand best). most shops in my area work mostly on Suzuki's and Yamaha's. I just would feel more at ease if it was done professionally as i plan to keep this bike for a long time, i really like it alot.

[StarGate]

You should be ok driving it there especially if you're not sitting in traffic. Just keep an eye on the temp gauge. You might even find you don't need to rejet after changing the exhaust. I'd install the new one and go for a ride to see how it performs. If it runs good and doesn't get hot, then ride it for a while and check the plugs to see if it's running lean or not.

[markbvt]

I agree with Stargate. Since you seem to be running rich right now, there's a good chance it'll be fine after you install the new exhaust.

If you do need to rejet, give the Kawasaki shop a call first to make sure they'll even work on your bike. There are an awful lot of shops these days that won't touch bikes more than 10 years old, and that refuse to tune carbureted bikes, probably because they don't have anyone on staff anymore who knows how to. (I mean, why should a young mechanic have to get his fingers dirty when he can just hook up a laptop and upload a new EFI map?)

--mark

[92NinjaZX6]

Thanks for your help guys, i love this forum! I'm going to install the Muzzy once it comes in and see what goes afterwards....just waiting for that damn UPS guy hehe.

[ZXNinjaboi]

Hi everyone. I own a 01' ZX7R and this is my first time I'm attempting to synchronize my carbs. The only thing is, one of my vacuum port is plugged off. (only have 3 ports to plug my carb sync into) Do I have to buy a replacement adapter to replace the plug or is there a trick to it.
Anyways, anyone who has experience and could help me out would be much appreciated

[92NinjaZX6]

Originally Posted by ZXNinjaboi

Hi everyone. I own a 01' ZX7R and this is my first time I'm attempting to synchronize my carbs. The only thing is, one of my vacuum port is plugged off. (only have 3 ports to plug my carb sync into) Do I have to buy a replacement adapter to replace the plug or is there a trick to it.
Anyways, anyone who has experience and could help me out would be much appreciated

Heh funny you say that because i thought someone intensionally plugged mine. #4 carb has a small short vacuum line that isnt connected to anything, when i look inside the hose, there is a ball bearing stuck in there to plug it up. Dont know whats up with that.

[WeBeToyz]

Originally Posted by ZXNinjaboi

Hi everyone. I own a 01' ZX7R and this is my first time I'm attempting to synchronize my carbs. The only thing is, one of my vacuum port is plugged off. (only have 3 ports to plug my carb sync into) Do I have to buy a replacement adapter to replace the plug or is there a trick to it.

Not sure why, but I know my ZX7 came that way as well. Kawi installed 3 ports & 1 plug, except for the models specific for CA (emissions, I'm guessing).

Unless it would be different for the Canada models (which I don't think it is, nor can think of a reason why it would be) you should have four ports to hook the vacuum lines up to. You can order adapter replacements from Kawi or you might be able to get them from Motion Pro.

If you have a cycle salvage in your area you may be able to snag one off a motor they have sitting around. As long as it is the correct thread it should work, regardless if it is off a Kawi motor or not.