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Discussion Starter #1
Hey guys, i have a 98 zx9r for my race bike. running a k&n high flow, and used to run a kerker can, just took it off cus it'll be in the way when i mount up my bars. rest of the exhaust is stock. just wondering what you guys who run straight pipes use for jetting.

Thanks in advance for the input!
 

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What's your current jetting and set of carbs (cvk or fcr)? No exhaust can/muffler will provide less back-pressure which will provide less scavenging. I know a few members on the forum who run track bikes like to use the stock/OEM filter instead of k&n. Any other mods done to the bike?
 

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I didn't drag race a bike but I did run open pipe (no muffler) and no air filter on my bike for a short period of time. Big difference on where the power band shifts from mid range to more toward the high rpm range. Which, this is what you want I take it. Just need to know your current jetting and type of carbs.
 

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Discussion Starter #4 (Edited)
carbs are stock CVK, i cant see a size stamped on my jets which would lead me to assume they are also stock, however im not sure since i think the needles might be shimmed. as for other mods, the engine is stock other than the air filter and the can (now removed).

anyone know for sure the stock jetting sizes and needle for the 98 ZX9R?
 

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You're going to need to upgrade to at least a stage 1 jetting kit to compensate for the can removal. You can either look into DynoJet jetting kits or keihin jets (stock/oem) or FactoryPro (FP). Staying w/ Keihin jets makes it easier when trying to figure what jets you need based on what you have. DJ uses their own measurement (flow measurement I think) for their jets. E.G. DJ main of 134 would equal a Keihin main of 185 (disclaimer: NOT a true comparison between the two jets). It's weird.

Stock jetting should be 160 main fuel jets. I would go to something equivalent to a 165 main fuel jet for carbs 2&3 and 162 for 1&4. You should also have a stock needle in there as well. You made need to remove the shims after rejetting. Stock carbs for the C model 9 is 41mm Keihin CVKs.
 

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Discussion Starter #6
thanks! so whats the idea behind the different sizes for cylinders 1&4 and 2&3? a little extra for heat regulation. i do have a jet kit that the previous owner was going to install but never did for 6 sigma racing. so ive got 170 and 180 mains (4 of each) and 42 pilots on hand. think i could make it work or go with a new one?
 

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thanks! so whats the idea behind the different sizes for cylinders 1&4 and 2&3? a little extra for heat regulation. i do have a jet kit that the previous owner was going to install but never did for 6 sigma racing. so ive got 170 and 180 mains (4 of each) and 42 pilots on hand. think i could make it work or go with a new one?
Thermal cooling or something along those lines. Since you've got 170's already, just install those 1st in all the carbs. It's not necessary to have stepped jetting. If the 170's in all 4 don't work out like you want, you can step it as 170/180/180/170. I'm not too worried about the pilots. Stock sizes are 38. You should be able to tune it with the idle mixture screw on the side facing the intake boots.
 
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