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Discussion Starter · #1 ·
so in short, 79 cx500D with k&n air filters and custom exhaust. i scared my local oem dealer on the phone 5 min ago.

he told me there is different carbs? and that i would have to bring in my current jets so he would know what i have. i said "i have no clue that their is different carbs out there"
. so in previous posts i heard 90/120 for jet sizes and that the stock jet sizes are 78/112. he also told me not to drill my jets. and that his shop would not touch the project for me. so please forum please help and is it true that i'll have to bring in my jets (put them in his hand) before he tells me what to buy?



i really dont know much about jets nor had i known there was a main jet and another jet per carb. i really dont want to destroy my cylinder's.

thanks, shorty.



http://i905.photobucket.com/albums/ac251/shortyidaho/DSCN1249.jpg
 

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Just did this, it is really simple, you'll need two of each jet, they are simple to replace.



Mike
 

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I have been told that there are 2 different carberators that these bikes use, although I, myself have only seen Kehnin carbs on these bikes. Hence, the why the parts guy wants to see 'em, I'd imagine.



Before ya go and purchase jets you may already have, you oughta take the carbs off and see what sizes you have installed. Stock jets are 78/112. The numbers are stamped on each jet
 

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so what sizes should i start guessing with?




The guessing would go like this.

90, 120, 125, 130.

If you don't plan on putting pod filters on the bike then 90, 120 should do just fine.
 

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They are both main jets



Mike
 

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The 78 would be on the "slow" main, and the 112 would be on the "main" main....lol.



Best bet would look into the "sticky's" posted at the top of this page to get pics of just WHERE these 2 sizes are supposed to be, as it DOES make a difference.
 

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The 78 would be on the "slow" main, and the 112 would be on the "main" main....lol.



Best bet would look into the "sticky's" posted at the top of this page to get pics of just WHERE these 2 sizes are supposed to be, as it DOES make a difference.




Bear,

You don't want to confuse him but I know what you're saying. Both of them are main jets and sold as main jets. There function is the same but in different holes.



The lower jet replaces the 78 jet in the carb which takes care of 0-1/2 throttle and at that point it switches over to the other main jet which replaces 112 or 115 and controls 1/2 throttle all the way to full.



The bigger number jet screws into the brass emulsion tube.



If you put the jets in the wrong spot you will have a rich o-50mph bike that will just go blah after that.
 

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so should i buy 90's for the idle and 120's for the highers?


Buy both 90 and 120 like this.



MAIN JETS price per each jet





OVERALL LENGTH = 8mm

HEAD DIAMETER = 6mm

THREAD DIAMETER = 4.9

 

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Discussion Starter · #17 ·
so in a situation like this i shouldn't worry about replacing the slow jet?

from my understanding there is only one main and one slow, (short, long) already per each carb. maybe thats whats throwing me off so much


do i buy 2 shorter 90s and 2 shorter 120s. having one short 90 and one long 120 for each carb



or



http://jetsrus.com/photos/photo_jet_keihin_k28.JPG

should get all 4 jets in the shorter (Main jet style) pictured above^ with the only difference being that one is set at 90 and the other is 120 per each carb



ie.




do i buy 2 shorter 90s and 2 longer 120s. having one short 90 'and' one long 120 per each carb



http://jetsrus.com/photos/photo_jet_keihin_k36.JPG



http://jetsrus.com/photos/photo_jet_keihin_k28.JPG



help im confused. again thanks for the patience

shorty from kuna (close to boise)



and hope this is not confusing
 

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I know this all sounds pretty scarey to ya, but it's NOT that difficult. Heck, I can take the carbs off my GL and have them turned upside down (WITH cables attached) pretty well balanced on a short piece of 2x4 and the spine of the bike in 15 minutes. And, that includes pulling the side covers, removing the seat and fuel tank.. After that ya got 4-8mm bolts on the intake, 2 screws on the boots (may wanna spray a bit of penetrating oil where the boots slide over the mouth of the carb so you can turn them striaght up, or at such an angle to simply grab holt of it and wrench its little neck right off the carb/s, and 2 screws on the airbox.......extract the carbs out from the left side of the bike, with cables still attatched, make a long backwards arc, so as to not kink the cables. Then, you'll need a phillips screwdriver to remove the float bowls (oh ya, there are 2 little rubber drain lines that you'll need to remove BEFORE you extract the carbs!),



I would use only good QUALITY tools. I thinks the 4-8mm bolts on the intake are stainless, but they are on there pretty tight and WILL round off, IF not attacked with good quality steel. A good six point and a good 12 point box end, NOT an open end! (don't ask me how I know this...lol)



Onced you get the float bowl covers off.........EVERYTHING you have read up to this point shall become ABUNDANTLY clear!
 
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