Jetting CV32 carbs for bore increase & other mods

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Jetting CV32 carbs for bore increase & other mods

19 Mar 2026 01:34
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Putting together a good fuel system is the last part of my project. Progress has been kind of slow but I want to do this right. I'm curious what other people here have done with similar engine mods. I know it can vary a lot I just want a general idea of what worked and what didn't work. Open to suggestions. Maybe save myself some time and $.
I built the engine for my KZ400 with +4mm pistons, shaved the head .5mm, light head porting, electronic ignition & coil relay, and I have an aftermarket 2-1 exhaust that might go on. It has higher compression and an extra 48cc over stock.
I tried a couple different things with my Mikuni setup but decided to use the factory Keihin CV32 carburetors off my 78 KZ400B parts bike. It was garage kept even after it slid on pavement so they are in nice rebuildable condition. A test fit showed they fit in the 74 frame well and line up with the factory airbox even with the narrower carb spacing of the later engine, so I'm using that too.
I ordered rebuild kits and a few different size jets from Dime City Cycles. My question is should I expect a big increase (or decrease?) in jet size? The engine will pull more air and thus more fuel so maybe it'll land pretty close to factory jetting? There is a jet under the rubber plug and I'm still not 100 percent clear on what it does, just that it's fed by the main jet. I'm learning as I go here so any info and advice is appreciated. 
74 KZ400 - 446cc

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Re: Jetting CV32 carbs for bore increase & other mods

19 Mar 2026 01:40
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Some photos of the carbs for your viewing pleasure:

 

 

 
74 KZ400 - 446cc

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Re: Jetting CV32 carbs for bore increase & other mods

19 Mar 2026 01:49 - 19 Mar 2026 02:06
#922347
You are likely to only need an increase of the main jet.
The jet fed by the main is the pilot jet and shouldn't need touching.
 
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
www.kzrider.com/forum/23-for-sale/611992...lide-mikunis?start=1






Last edit: 19 Mar 2026 02:06 by zed1015.
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Re: Jetting CV32 carbs for bore increase & other mods

Today 22:10 - Today 22:13
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Thanks zed that makes sense. These have two main jets and I ordered a few different sizes of each so I should be good to go. I'll update later with what ends up working best.
I made a note for my own reference might as well share it here too.
stock:main 70 second main 90 pilot 35
ordered:main 68, 70, 75, 78
second main 88, 95, 98
pilot 35
74 KZ400 - 446cc
Last edit: Today 22:13 by quantity. Reason: formatting

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