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Discussion Starter · #1 ·
I am getting ready to order new jets for my carbs. When looking on Jetsrus.com they do not have the sizes I need for my slow jet in that category. I have heard that I can buy both a 90main jet and a 120main jets instead of a 90slow jet and 120main jet. Not sure if that made sense. What Im asking is if there is a difference in the SLOW and MAIN jets other than the inside diameter, are the length and threads interchangeable? I just ask because on the Jetsrus.com website it says that they length and diameter of the SLOW jets are different than the length and diameter of the MAIN jets. Thanks for the input

Cody
 

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Larry would know, but I do know people have accidentally switched them so apparently they'll screw in that way.



Jet R Us didn't have the right one? That's odd, but they're not the only supplier. Also - when it gets to tiny parts like that it's often cheaper to buy them at the dealer or a carb shop instead of paying all the shipping.



Make some local calls.
 

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Both the 90 and the 120 jets are called a main jet. The main jet in our carbs are the larger ones and they go in the brass emulsion tube. The smaller jet is the secondary main jet and is screwed into the aluminum.

The slow jet you are referring to is not available by jetsrus. What they are listing is for the later model carbs the have the screw in low jet. You have carbs with a press in low jet if it's the 78 that you have in your signature. They can only be removed with the 5/64" EZout.





This will show you where the jets are.

 

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Discussion Starter · #4 ·
Thank you Larry,

So for my specific situation (pod filters and H-box removed) would it be sufficient to only replace the two main jets to a larger size, or would there be other jets that I would need to replace with the other two? Does the Low Jet need to be replaced? If the Low Jet needs to be replaced what size would you recommend? Just to recap: the two sizes that are referred to commonly as 90/120 are both main jets (primary and secondary) both are screwed into place. The low jet is a press-in version and not available by jetsrus.com for my model bike (78 cx500).

Thank you for all of your knowledge and helping me with my build

Cody
 

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No other jets need to be replaced. But most guys end up turning the mixture out to 3 turns. The low jet needs to be cleaned out well if your not going to pull it. If you have my book it outlines that procedure. If not, the low jet has a .018" hole that needs to be cleaned out with a micro drill bit. You can get those a local hobby shops. But changing the low jet is not needed for what your running.

 

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How did this work for you, Cody? I'm running a set up similar to yours and need to reject as I have a dead spot around 5k rpms.



FYI to those that read...I'm running pods, sportster exhaust w/no baffle, and no h-box...all the previous owners doings.
 

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Kind of in the same boat here. Just picked up mine a month or so ago and I'm trying to get everything running and ship shape. I'm planning on ordering a new set of jets for my planned carb rebuild but I'm unsure just yet which to go with. Everyone seems to lean to 90/120 but I dont know which direction to go. Im running stock on the airbox but the exhaust is dual sans H-Box.
 

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Both the 90 and the 120 jets are called a main jet. The main jet in our carbs are the larger ones and they go in the brass emulsion tube. The smaller jet is the secondary main jet and is screwed into the aluminum.

The slow jet you are referring to is not available by jetsrus. What they are listing is for the later model carbs the have the screw in low jet. You have carbs with a press in low jet if it's the 78 that you have in your signature. They can only be removed with the 5/64" EZout.





This will show you where the jets are.

What should I buy?

I'm looking at Keihin carburetor jets and parts main jet slow air pilot kit
 

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depends on your bikes year of manufacture , what modifications you have done to it - pods , removed H-box etc
 

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that tends to be the starting point . Some folk play about with jets either side of those to fine tune to their exact needs , but 90/120 will cater to most needs.
 
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