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Discussion Starter · #1 ·
I'm trying tune low end and am trying to find out what size main jets to start out with...some say stock are too big...what does everyone else have as mains w/ you're basic mods(filter and bolt on)???
 

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low end tuning will not be the main jets, if anyting it will be the pilot jets. This is because main jets will affect your top-end range. I'm guessing you have a filter and a bolt on exhaust and there is a flat/soggy spot when you give throttle at lower rpm's? well if this is the case, DO NOT change your pilot jets! first, you need to shim the carb needles and see what that does for ya.


... what problems are you having with your bike dude?
 

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Discussion Starter · #3 ·
I'm just trying to get another opinion on what size mains I should start off with and of all the other jets, floats,and mixture settings every one else is set at...

Check my other thread - "AAAARRRRGGG...stupid bike" that'll give you the skinny on my problem...


One reply seems to think stock jets are way too big for a 6...I'd like to see if any others feel the same...
 

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I have a Factory jet kit on mine. Main jets were actually leaner than factory. I believe I'm running a 132.5 on the outside and a 125 on the inside .(or vice-versa) I have the new needles at #3 and I forget what the pilots jets are. I think my pilot jets may be a little rich, oddly enough. I also have my fuel screws at the factory 2.5 turns out.
This is all out of memory, I'm about 7000 miles from my bike at the moment. I think I brought my jetting notes here, but I gotta look for 'em.
 

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for my wife's bike, I went down 10 (ie. 150 to 140) on the main jets and shimmed the carbs and set the screws at 2.5 turn out.

No dyno scession, but it pulls better and is super smooth......There is more tweaking, but for a stab in the dark it's real close.....

J
 

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Discussion Starter · #6 ·
Sweet jesus....THANK YOU....finally some direction....I still cant believe out of like 400 views on last post and after several others only 3 or 4 responses,but thank you,now I have direction to go in! I mean,I know the same bike can have different jetting req. for diff. mods but a bolt on can and air filter arn't goin to be that much different for thousands of the same bike...


Badass...what bike does your wife ride...a 6r/zzr?
 

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well my main jets (uk) zx6r j 2000 are 155 on cylinders 1 and 4 and 157.5 on 2 and 3. that is standard.
i have been told that most 'tuners simply swap the inner two onto the outer 2 cylinders and buy some 160's for the middle two. a tiny shim under the needle as opposed to raising it a full notch which - i am told is usually way too much.

HOWEVER - usa specs may be different.
what also confuses things is that the jets in the jet kits offered by dynojet are numbered 140 but are actually bigger than my 155's. the numbering is different. maybe to stop prospective customers simply buying mikuni jets in that size and saving lots of money.
it would be nice to know what size standard main jets are in usa.
 

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Discussion Starter · #9 ·
I do have a dynojet kit...the jets are numberd much smaller,but to me they also look like much smaller jets(i.d.)I'm hoping the size i need I'll have in there,yea I wish I could corrospond dynojets to mikunis...
 

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here's the trick.............

take a carb needle, use it as a depth guage.....meaning, take a main jet and slide it up the needle till it stops, place your thumbnail at the stop point, and remove and slide the other brand jet up the needle....it will stop short or slide farther up the needle....regardless of numbers the hole sizing is key......they have to be the same style or you will get fooled because the different jets can have the hole deeper in the jet, making it appear to be different when it might not be.....


does this help?
 

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i got an email from dynojet saying their jets were size 140 and mine are 155 and 157.5. however a dynojet 140 is not the same as a mikuni 140:rolleyes:

so a lot of folk will be thinking they are going smaller yet they prob arent.
i assume factory pro and ivans use the same misinformation process.
as i said before, for less than 10 dollars we could have the same half to full throttle performance as their kits. if only we knew what size jets were in their kits.
i assume all the jet kits use slightly bigger jets in the middle two cylinders
 

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I cleaned my carb today and found that 1 & 4 carbs jet was a 118 and the 2 & 3 carbs were 125 i think. Is that stock on a 2001 zx6r? The jets in speaking of are the ones inside the float bowls.
 

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Just bought a 1991 zzr600 and it has had a dynojet kit fitted recently and a motad nexxus exhaust. Does anyone know which would be the best jet size for this particular exhaust as the kit says a 140 with a standard pipe and a 144 with a free flow pipe and I assume the nexxus is not a free flow. There is also a 136 jet with no mention of it in the instructions.
 

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hi tribal wolf, i live about 4 miles from you in west hull!!!
i think uk bikes are a bit more tuned up than a lot of usa bikes as standard.
as i keep saying jet kits have irrelevant numbers to standard.
i would do a search on here. i have 160 and 162.5s mikuni on mine (plus an akrapovic full system and it out accels my pals gsxr600 04 and 08 models.
they only cost about 3 quid each and so i bought 4 and together with my 4 standard jets (155 and 157.5 i think )i just messed about till i was happy.
my bike is a zx6r 00 which is the same as a zzr 08 i believe.
 

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This may not be too relevant but here is a cross reference for different jet manufacturers i found on another forum. I cannot vouch for its accuracy though.

Width------Kehein # -- 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
 

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Thanks for the replies, I swapped the jets to the smaller ones from the dynojet kit and it definitely ran better but still not happy with large throttle openings. I have now bought some standard carbs from ebay but I am at a loss. The carbs I have bought have a series of pipes(see image) which the carbs on my bike don't have. I am not sure where to connect it to.



I think where they push into the carbs is blanked off on my bike. It looks like a fuel return?
 

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Ok, I have to post here as I cant start a new thread yet(too new a member).

I fitted the standard carbs after stripping, cleaning and adjusting etc, balanced them with a carbtune and it idles nice and smooth and is fine around the doors. If I am on a slip road for example and I bang open the throttle it does exactly the same as with the original dynojetted carbs and bogs down badly. I am a mechanic and have worked on many high performance cars but bikes are new to me and due to illness cant really spend a lot of time messing with it, so I ask has anyone got any ideasas to what may be the cause??
 

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does it misfire through being too rich - stuttering or just makes a loud intake sort of roar ie weak?
did you move the needles? i keep forgetting you own a zzr and not a zx6r and i assume the carbs will be totally different.
on my zx6r the needles have notches and i ve tried raising a full notch but it runs too rich, misfires in fact.
however a small washer 0.5 - 0.75 mm ish under the needle worked fine. just put my original pipe back on before mot at a&m up the road from you and it still runs fine.
 

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I figured I would ask in this thread rather than starting a new one about jetting changes. I have a 2001 ZX6R and it sat for a while. The bike will not idle without the choke on partially so Im going to be replacing the pilot jets and while I was there I wanted to possibly get different main jets. The bike is stock. Would you recomend staying with the stock sizes or going with something a little bigger and shimming the needle? I will not spend money on a jet kit so use Mikuni sizes please.
 
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