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Discussion Starter · #1 ·
Hello all! This is my first post here, im so glad I found this website I've been reading a lot the past few days, and what a great site! But, I still have some questions to hopefully get this bad boy tuned perfectly.

I recently purchased a 1994 ZX7-L. From what I can see it has a Yoshi RS3, k&n filter, float bowl mod, and a jet kit of some kind.

So, the main jets all say "FACTORY 200K". Is this factory pro? And what jet size is that?
The needles are set with the e clip at 3rd clip down, and two washers above the clip on 1 and 4, and one washer on 2 and 3. My reason for this is one carb only had one washer above the clip. So I figured since most run bigger jets in the middle and mine are all the same, I could make it slightly richer on 2&3 by using only one washer. Is this ok?
Most of the floats were around 10-11mm, #3 was at 12mm. I set them all to 13mm.
Pilot screws were at 1 1/2, I set them to 2 turns out.

Now how it runs...
PITA to start cold. Once going, i set the idle, it idles fine. At first. Then as its warming up, and throttle is blipped, it starts to hang around 2-3K rpm. This gets worse as it warms up, the "hanging" lasts longer. What does this mean?
Also when warm the idle starts to die out, so to compensate i turn the idle screw in, a good amount. And it'll idle, but really likes to surge up to 2-3k for awhile then go back down.

Besides idle and cold starting, she's great. Starts warm just fine, and blows my ass off at upper rpm.:scared

Any help is much appreciated.:smile
 

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Discussion Starter · #2 ·
I tried running it with the mixture screws at 2 1/2. Really boggy. I set the screws back to 1 1/2 out and the throttle response was better.
Never has it dipped below set idle and returned, thus indicating a rich mixture. Even though I'm pretty sure it was rich.


After it is warm and idling at 1k, and you blip the throttle it sticks at 2-3k. So when I reduce the idle speed screw it goes back down to 1k, but then it likes to die.
When the engine is off and warm, it will not start unless I turn the idle screw out all the way and use slight choke and playing with the throttle when it starts to cough. It coughs a lot starting. Starting it basically waiting to get enough "cough" until i can give it throttle and then it roars to life. I have to then hold throttle and set idle speed so it won't die. Then it idles great, doesn't skip or move. But, slight throttle and it snaps to 3k and holds, sometimes falling back to 1k.

With the floats at 13mm and the mixture screws at 1 1/2, I'm wondering if its too rich to start. Maybe I should raise the float height, making it more lean, then turn the mixture screws more rich?
Does the float do anything at idle? Or low rpm very small throttle openings....

And does anybody know who makes "FACTORY 200K" jets. If these jets are comparable to kiehin size 200's... then im at a loss.

Im confused. I just need it to start and idle. When moving, she's great.
 

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if the revs are hanging before dropping down to idle its usually the air mix screws or float height.
As far as starting goes my L1 was a pig to start but once its in regular use it gets better, have you cleaned/changed the plugs?
 

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I tried running it with the mixture screws at 2 1/2. Really boggy. I set the screws back to 1 1/2 out and the throttle response was better.
Never has it dipped below set idle and returned, thus indicating a rich mixture. Even though I'm pretty sure it was rich.


After it is warm and idling at 1k, and you blip the throttle it sticks at 2-3k. So when I reduce the idle speed screw it goes back down to 1k, but then it likes to die.
Try 2 turns out, even. Then get your carbs synchronized.
 

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Q: So, the main jets all say "FACTORY 200K". Is this factory pro? And what jet size is that?
A: Factory Pro is the brand. 200 is the jet size... which seems massive. My carbs have a Factory Pro kit in them and I'm running 178 on the inside carbs and 168 on the outside carbs.

Q: The needles are set with the e clip at 3rd clip down, and two washers above the clip on 1 and 4, and one washer on 2 and 3. My reason for this is one carb only had one washer above the clip. So I figured since most run bigger jets in the middle and mine are all the same, I could make it slightly richer on 2&3 by using only one washer. Is this ok?
A: Firstly if you have clips on the needles, then they are probably Dynojet needles. Mixing factory pro and dynojet kit isn't recommended. All the components in a jet kit (key word kit) are designed to be used together. So I'd throw out the dynojet stuff and get some stock needles since that is what the factory pro kit uses (although with different vacuum springs).
As for your question, putting washers above the e-clip does nothing. Putting washers below the e-clip richens the mixture. If you want to richen the mixture of the middle carbs you'd want to put MORE shims under the needles...


Q: Most of the floats were around 10-11mm, #3 was at 12mm. I set them all to 13mm.
A: 13mm is the stock float bowl height... which is already too rich with 180 main jets and your using 200! With the factory pro kit, the float height should be 15mm so I'd say at the very LEAST set it to that.

Q: Pilot screws were at 1 1/2, I set them to 2 turns out.
A: 2 turns out is what I have mine set to. As the days get colder I go to 2.5 to make the bike easier to start.

Q: PITA to start cold. Once going, i set the idle, it idles fine. At first. Then as its warming up, and throttle is blipped, it starts to hang around 2-3K rpm. This gets worse as it warms up, the "hanging" lasts longer. What does this mean?
A: 2 turns out will almost certainly require some choke/effort to start... even in Maui. another quarter or half turn out will make it easier to start and will still run fine down low.
RPMS hanging is an indication of lean tuning but the problem should get better as the bike warms up.... so your problem might be something else... a vacuum leak maybe?


Q: Also when warm the idle starts to die out, so to compensate i turn the idle screw in, a good amount. And it'll idle, but really likes to surge up to 2-3k for awhile then go back down.
A: This is almost certainly due to a vacuum leak somewhere. Check the vacuum adapters and bolts under the intake boots. Sometimes back firing can shoot off one of the vacuum plugs. Check the intake boots themselves for damage and make sure that they are tight around the carb intake spigots. Also check the carb diaphrams for damage.

To get your carbs running right I'd say you need to:
- Get yourself a Factory Pro jet kit
- Take all your jets out, soak them in carb cleaner
- Spray carb cleaner through your carb bodies
- Blow compressed air through everything
- Install the jet kit according to factory pro's reccommendations.
- Install and balance your carbs
 

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I tried running it with the mixture screws at 2 1/2. Really boggy. I set the screws back to 1 1/2 out and the throttle response was better.
Never has it dipped below set idle and returned, thus indicating a rich mixture. Even though I'm pretty sure it was rich.
Dipping below idle indicates a rich low rpm behaviour. 2 1/2 turns out on the idle screws isn't unreasonable. I'd bet your main jets and float heights are to blame. Believe it or not, main jets effect fueling as low as 1/8 throttle opening... and of course float heights affect everything.

After it is warm and idling at 1k, and you blip the throttle it sticks at 2-3k. So when I reduce the idle speed screw it goes back down to 1k, but then it likes to die.
Vacuum leak methinks

When the engine is off and warm, it will not start unless I turn the idle screw out all the way and use slight choke and playing with the throttle when it starts to cough. It coughs a lot starting. Starting it basically waiting to get enough "cough" until i can give it throttle and then it roars to life. I have to then hold throttle and set idle speed so it won't die. Then it idles great, doesn't skip or move. But, slight throttle and it snaps to 3k and holds, sometimes falling back to 1k.
Probably a bunch of different factors at play here. The 7s don't like to start hot anyways. The fact that you have to mess around to start the bike when hot isn't a massive indication that anything is wrong one way or another. The fact that only idles high or dies still seems to point to a vacuum leak

With the floats at 13mm and the mixture screws at 1 1/2, I'm wondering if its too rich to start. Maybe I should raise the float height, making it more lean, then turn the mixture screws more rich?
Use 15mm AT LEAST with your massive main jets

Does the float do anything at idle? Or low rpm very small throttle openings....
Float height effects everything

And does anybody know who makes "FACTORY 200K" jets. If these jets are comparable to kiehin size 200's... then im at a loss.
AFAIK Factory 200 = Kiehin 200... Someone will have to correct me on this if I'm wrong

Im confused. I just need it to start and idle. When moving, she's great.
While the symptoms are only at the low end of the RPMs, the problem could be caused by needles and main jets as well. Ditch the salad of jet kit parts in the carbs now for either stock stuff or FP stuff. Don't waste time with Dynojet kit.
 

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AFAIK Factory 200 = Kiehin 200... Someone will have to correct me on this if I'm wrong
Width------Keihin # -- DynoJets # -- Mikuni #
0.0350---- 92.5--------- 92-----------86.3
0.0360---- 95----------- 94-----------88.1
0.0370---- 97.5--------- 96-----------90.0
0.0380---- 100---------- 98-----------91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

Keihin "393" series:
The Keihin sizing is pretty close to right. Close enough for hand drilling a jet when you don't have what you need. A 150 is 1,50mm in diameter.

Factory Pro "K Series":
The Factory Pro "K Series" jets are dimensionally sized, just like the Keihin jets.
Example: a "150" Keihin or "K Series" main jet is usually, 1.50mm in diameter.

According to dynojet, http://planetminis.com/f21/finally-f...ets-52984.htmlthe dynojets are supposed to be sized the same as Keihin (dimensionally)- but I've never found that to be true.
As far as different lead-in angels and such, I'm guessing that that difference is more that metric manufactured jets tend to have a std 90 degree included angle and USA manufactured jets tend to be 82 degree included angle. I could be wrong on the lead-in angle - as it was 15 years ago that we started making Keihin style jets.

Mikuni N102221 (small round slotted jets)
That part of the chart is just wrong. You have to take a selection of jets, across the range and measure them.

Summation -
If you have a pile of a certain brand of jet and you want to use them, it's up to you. I've seen and tuned Keihin carbs jetted with Mikuni jets that "squeak" that last 1/2 turn (the threads are .05mm different) and vice versa. Heck - I've even used dynojet jets if there's not anything else available.

But - if you are using a particular brand of jet, don't swap brands of jets using this dj and Mikuni cross reference chart

Thanks -

Marc Salvisberg
Factory Pro Tuning
 

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But - if you are using a particular brand of jet, don't swap brands of jets using this dj and Mikuni cross reference chart
I mentioned this already but along similar lines; don't mix jet kits either.

The Dynojet and FP kits (most common ones) have VERY different approaches to tuning the carbs.

Stuff from one kit will most likely mess up the intended tuning on another kit.
 

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Discussion Starter · #9 ·
Thank you all for the replies, extremely helpful!
Kinda has me wondering what the PO was up to... There are a few strange things I found. I will be busy in the lab again... and i'll post how it turns out.
 

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man, thank you guys. I just picked up a 94 zx7, and she is a basket case. I cleaned the carbs and noticed the mixture screws were set pretty far out. I was gonna wait till I got her running to mess with them (not knowing where they should be close to). y'all just saved me a ton of time and burnt knuckles.
 

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Q:

Q: The needles are set with the e clip at 3rd clip down, and two washers above the clip on 1 and 4, and one washer on 2 and 3. My reason for this is one carb only had one washer above the clip. So I figured since most run bigger jets in the middle and mine are all the same, I could make it slightly richer on 2&3 by using only one washer. Is this ok?
A: Firstly if you have clips on the needles, then they are probably Dynojet needles. Mixing factory pro and dynojet kit isn't recommended. All the components in a jet kit (key word kit) are designed to be used together. So I'd throw out the dynojet stuff and get some stock needles since that is what the factory pro kit uses (although with different vacuum springs).
As for your question, putting washers above the e-clip does nothing. Putting washers below the e-clip richens the mixture. If you want to richen the mixture of the middle carbs you'd want to put MORE shims under the needles...
I mentioned this already but along similar lines; don't mix jet kits either.

The Dynojet and FP kits (most common ones) have VERY different approaches to tuning the carbs.

Stuff from one kit will most likely mess up the intended tuning on another kit.
Apparently you are confusing Factory's method of carb tuning of the 96+ ZX7R and the 93-95 models.

The 93-95 Factory kit comes with new needles that have the adjustable clip positions. 3rd clip down is the most common, as is installing a washer above the clip to help with the spring retainer.

Similar to the DJ kit that ALSO includes new needles and 6 positions for a clip.

Josh
 
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