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Discussion Starter · #1 · (Edited)
I hate carbs!! Fixed!!!Stupid alternator....

Ok guys I need to pick some brains. Hopefully there are some here. My 89 zx7 H1 model I'm having issues with it falling flat on it's face at 8k or higher. If I can get it to go past 8k it just stops pulling. Anything under 8k it pulls hard as hell. I have cleaned the carbs, sonically. Changed fuel pump/filter, and checked for all the fuel lines to make sure they aren't failing or crimped, or anything else that may be out of the ordinary. My mods are as follows. Valves are adjusted,

Stock engine
Muzzy stainless header
Yosh mid pipe and slip on
UNI air filter with unmodded stock air box.
38mm cvk carbs (stock were 36mm)
Stock pilot jets
DJ needles (number unknown)
and FP 122's on the outers and DJ 122.5 on the inners.


Someone please throw some ideas I can work with as I'm running out.
 

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Discussion Starter · #3 ·
Yeah thanks Claps. I have read that over and over again. The problem is sometimes the bike pulls great to redline, and sometimes it just falls flat on its face. So this is why I'm stumped.
 

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Quinton Phuckin Tarantino
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I hate crabs too they get so itchy... Oh you said carbs never mind . Does it always drop out @ the same rpm ? Or does it change ? You could try taping off the air box inlet to about 25% of its normal size to see if its running lean or not . Other than that are you sure It's the carbs ? Are you getting spark @ high rpm? How old are the plugs? When I rule out the carbs the first thing I check is the electricals . I had a bike with a bad kill switch drive me nuts before .
 

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I dont know much about that particular model, and what kind of ignition coils it has, but it wouldn't hurt to do a resistance test on it or them. When a coil starts going bad, it can have a threshold where it just stops firing at a higher rpm!

Good luck Kitty!
 

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Ok guys I need to pick some brains. Hopefully there are some here. My 89 zx7 H1 model I'm having issues with it falling flat on it's face at 8k or higher. If I can get it to go past 8k it just stops pulling. Anything under 8k it pulls hard as hell. I have cleaned the carbs, sonically. Changed fuel pump/filter, and checked for all the fuel lines to make sure they aren't failing or crimped, or anything else that may be out of the ordinary. My mods are as follows. Valves are adjusted,

Stock engine
Muzzy stainless header
Yosh mid pipe and slip on
UNI air filter with unmodded stock air box.
38mm cvk carbs (stock were 36mm)
Stock pilot jets
DJ needles (number unknown)
and FP 122's on the outers and DJ 122.5 on the inners.


Someone please throw some ideas I can work with as I'm running out.
I'm out.:angry
 

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Discussion Starter · #8 ·
You know Rocket thats an Idea. It almost gets to a specific temp then it runs fine. Then anytime after that above or below it acts like its just falling flat on its face. My AFR gauge I have also reads dead lean as well so.
 

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Discussion Starter · #9 ·
Cam anyone tell me what size jets are in a Factory pro or Dynojet stage 1 jet kit or my bike? 89 ZX7. Also the same ones that are in the same kit for the 90.
 

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Discussion Starter · #11 ·
Well from what I read in my service manual, the stock jets are 112's or 118's depending on it being a cali model or not. I got the bike with I assume DJ 126's (which I can't find right now). I am running 122 FP on the outers and 122.5 DJ on the inners. The only think I can figure is since the DJ's measure in CFM and not diameter size like the FP's that could be my issue. I am at the point of just getting a FP jet kit and hope for the best.
 

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This should solve your problem.

 

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Well from what I read in my service manual, the stock jets are 112's or 118's depending on it being a cali model or not. I got the bike with I assume DJ 126's (which I can't find right now). I am running 122 FP on the outers and 122.5 DJ on the inners. The only think I can figure is since the DJ's measure in CFM and not diameter size like the FP's that could be my issue. I am at the point of just getting a FP jet kit and hope for the best.
Thats correct They are not sized the same.
 

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Well from what I read in my service manual, the stock jets are 112's or 118's depending on it being a cali model or not. I got the bike with I assume DJ 126's (which I can't find right now). I am running 122 FP on the outers and 122.5 DJ on the inners. The only think I can figure is since the DJ's measure in CFM and not diameter size like the FP's that could be my issue. I am at the point of just getting a FP jet kit and hope for the best.
Kiit,

Here's some info from Marc Salvisberg (He's the President of Factory Pro Tuning). He posted this on Factory Pro's website a long time ago. It's the conversion chart for carb jet sizing.:

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...-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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Kitty wasn't your bike running OK before this? Did this just start happeneing? I was just wondering why you thinks the problem is due to jet sizing?
 

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Discussion Starter · #16 ·
Its been doing this for a while. Just recently though coming back from my trip to cali she's gotten more consistent in her temper..I wish I could find the 126's I pulled from the carbs to start.
 

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My bike does this when the fuel filter I installed gets plugged up.
 

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Discussion Starter · #18 ·
I just installed a new filter and it got worse LOL. After doing to jet reading I found out what needs to be done. Turns out I was looking at it all wrong. According to the jet chart 2fat2fly posted, I need to install my 126's in the middle carbs and call it a day as the 122.5's are smaller than the 122's I have on the outers. So Change them all to DJ staggered 122,126,126,122 will put me right around 130,135,135,130 Keihin. Then fix my slides and pilot settings then hang on.
 

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Quinton Phuckin Tarantino
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Usually the best way to jet the mains is to start rich and lean out from there . If you use all the same jet in all 4 carbs this will be a lot easier to get it close and then do your fine tweeking by putting the slightly richer jets in the center carbs .
 

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Iron8 is right and another hint is run the same size mains all the way across. When you go up or down in size do it in increments of 5 such as 130 to 135 and down 135 to 130. You will not notice a difference with the in between sizes by the butt dyno.

Idle jets will go from 0 to maybe 3000 then needles go 3000 to 6000 and above that is all main jet so you have to figure out from there where the difference is and what has to be changed.

Factory idle jetting is usually good for all around street purposes but stepping up into bigger carbs can make tuning considerably harder and confusing.

Small example on a ZRX1200 Kawasaki with stock 36mm and pod air filters the main jet will be 130 to 135 for around town fun now change to 40mm Ninja carbs and the mains go 200 plus so welcome to the world of carb confusion.
 
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