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Smaller carbs for kz750-4

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18 Jul 2022 23:14 - 19 Jul 2022 03:35 #870599 by zed1015
Replied by zed1015 on topic Smaller carbs for kz750-4

VM26 carbs are probably not what OP is after - they are a good 'upgrade' if you want top end power as they will not have the restrictions that the cv carbs have. A 26mm slide carb cannot be compared to a 26mm CV carb. As noted here, the VM26 came stock on the 900s and 1000s - they will work on a 750 but you probably won't see any real gains unless you're combining with head and exhaust work that needs extra flow at high rpm.

I can't say for certain (I've never done it) but I would expect that putting a slide carb from a larger engine onto a smaller engine that had CV carbs would just kill the low-mid torque for the sake of high rpm performance, exactly what OP wants to avoid.
Well! i've done it quite a few times on the 650 and 750's
Nobody is comparing VM's size for size with CV's.
You will see overall gains with the vm26's of both power, torque and response on a stock motor and they don't kill the bottom end or midrange.
Jetted and set up correctly they perform smoothly from idle to the redline.
24's are a bit small and limiting for a 750 and won't gain any low end torque as the RPM point where peak torque is produced is goverened more by engine spec, compression and cam timing etc, not carburation or venturi size.
Smaller carbs ( like for like , CV to CV or VM to VM  ) only increase low end response ( an illusion of more power or torque ) due to faster air flow through the smaller venturi at the expense of restricted air flow capabilities higher up and won't increase actual power anywhere in the rev range ..
May as well just fit lower gearing for more pull midrange ( and everywhere else at the expense of top speed ,increased rpms for a given speed and lower comparable mpg) to achieve the closest equivalent ( again just an illusion of more power/torque) to that unless he want's to get more involved and close up the cam lobe centers which is the only real way to actually move the torque lower down the curve.

 

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Last edit: 19 Jul 2022 03:35 by zed1015.

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