Categories: Ask MO AnythingFeatures

Ask MO Anything: How Do I Know Which Cylinder Isn’t Firing?

Dear MOby,

Help! My ’97 ZX-6R Kawasaki is running rough. Somebody said it sound like it’s only running on three cylinders. I replaced all four spark plugs, and all the wires and plug caps look fine, but it still sounds sputtery and sad. Another friend suggested maybe a plugged jet in one carburetor? Do I need to take all the carburetors apart or what? How can I tell which cylinder is the one that’s “missing”?

Raggedy Andy
Tucson, AZ

Dear Ragged,

Yes, if all the plugs are firing but one cylinder (or two) isn’t, it’s probably a fuel delivery problem and probably something is wrong in one carburetor. In a perfect world you’d rebuild all four of them (since you’ll have to take all four off in one chunk anyway), but in our world, why take all four apart if you don’t have to?

Here’s a trick straight from the 1980 Kaz Yoshima/ Ontario Moto-Tech playbook: Fill a squirt bottle with water, start the engine up, and spray each head pipe with a squirt. The water will flash into steam instantly on the “live” cylinders, and it’ll drip onto the ground on the dead one(s). That cylinder’s your problem.

And if it’s not that carburetor, when’s the last time you checked your valve clearances? Too-tight ones can also cause a misfire. Good luck and happy squirting.

Direct your motorcycle-related questions to, though some say we’re better at non-motorcycle-related ones…


John Burns

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