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Discussion Starter · #1 ·
hey folks, this is my first post here. i've spent some time searching the forum for an answer, and i kinda got what i was looking for, but i wanted a little more clarification. okay, so i am rebuilding the carbs on my '81 cx500, and this is my first rebuild. i'm going to run pod filters and straight pipes (once my custom project is back together) and i've found through reading this forum that i should probably go for a 90/120 re-jet. i've found a couple good spots to buy jets on the innerwebs, Jets R Us and SiriusConInc. My question is, regarding the 90/120 numbers, am i correct to assume it means a 90 slow jet and a 120 main jet? if so, Jets R Us only has slow jets up to a size 80 (and the other company doesn't seem to have slow jets at all). If that first number is in fact meant to be the slow jet size, then maybe I could do a 80/120 re-jet? any help would be appreciated...if this info already exists on this forum, i must have missed it, feel free to point me in the direction. otherwise, yeah, any words of wisdom are greatly appreciated. i'm trying to do all the work on this bike myself...i'm currently working on cutting down my throttle and clutch cables to a more friendly size for clip-ons, if i can tackle that, i should be able to rebuild these dang carbs.
 

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It is with no doubt 90/120, however pods AND straight pipes may call for a tad more than the 120.



Somewhere on the internet is a drill size chart you can use to open up the jets you already have. It takes those sometimes hard to find numbered drill sizes and I'd only do it with a "pin vise drill" or whatever they call the things that are like an X-Acto knife to hold small bits and use them by hand.
 

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Bingo, we should put this on the reference area:



http://kzrider.com/archive/viewthread.php?action=attachment&tid=15665&pid=135094



If that won't link it came from http://kzrider.com/archive/viewthread.php?tid=15665



Guess you learn something new every day, a 130 jet is 1.3mm and it's all metric based.



1.30mm = 0.051" (SAE) = 1.300mm = 130.0 jet size



Here are the common numbered drill sizes you can find most anywhere:

http://bobmay.astronomy.net/misc/drillchart.htm



If you need the precision ones http://www.mcmaster.com
 

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I have pods and straight headers. I have mine set at 90/130. I think my mixture screw is 2.5 turns out. Plugs are just about perfect. A little fat, but nothing to worry about.
 

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Discussion Starter · #5 ·
awesome...thanks for the info folks!
 

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Jets r us has everything u need. Just when u order, order everything u would need because shipping and handling is a flat 7.50.
 

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Discussion Starter · #13 ·
@ncjasen, i got my jets at a local shop...87.5 and 130. the idle jet in the keihin carb is fixed, non-removable, so what you're replacing is the primary main and the secondary main...weird, yeah. but they're both the same type of jet, so you'd probably be ordering from the "main jets" selection. i almost ordered from jets-r-us, but was confused about the idle jet thing, so i went to a local shop and the owner, Bud, informed me of the primary and secondary situation...and of course he's like "hang on, i have those jets here somewhere". so there you go. i haven't replaced mine yet, i'm going to take the carbs down and clean the hell out of everything in the process.
 

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I am having the same problem. i got 90/125 with the same setup as you but i'm running so damn rich i'm burning it off in the pipes. i just went back to 78/112 but i'm having a bitch of a time tuning it for that. we just had a major temperature drop in my area and when i jet it w/ 90/125 it was hot. now its much colder. good luck with your set up, mines kicking my ass!
 
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