1978 Kawasaki KZ650C Mikuni Mixture


Motorcycle Classics tech expert Keith Fellenstein
Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.


Mikuni mixture

Q: I could use some help setting the mixture on my carburetors for my 1978 Kawasaki KZ650C. How many turns out on the air/fuel mixture screw do you go to adjust a Mikuni carb? Remember there are four carbs on this bike.

Brian Rhenlun/via email

A: It’s almost universal that idle mixture screws are set at 1.5 turns from gently closed. Start there and turn them all out 1/2 turn and see if the idle speeds up. If it does, go a further 1/2 and check again. If no improvement try a 1/2 turn in from your start position and do the same test. Once you have figured out the right direction, fine tune in 1/4 turn increments. Once you have the fastest idle, use the idle speed screw that controls all four carburetors at once to set the correct speed. After that you may need to go back and double check the mixture. It can take a while to get it just right.

1/23/2020 9:33:46 AM

Back when I was a Honda mechanic I used to set idle mixtures by ear as well on all singles, twins and 4 cylinder Hondas as part of a tuneup, because you never knew what the owners had messed with. On 4 cylinders, it is best to synchronize the carbs first though with a set of vacuum gauges.

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