MO Maintenance: Clean Your Filthy Carburetors

John Burns
by John Burns

Meanwhile on Facebook, where all us old guys hang out, the great Joe Gresh wants to know how best to clean this truly heinous carburetor from his Kawasaki Z1 project? He probably already knows, since Gresh is a master of many mechanical disciplines. Maybe master is the wrong word, but he seems to keep lots of old things running, builds plenty of new things, seems to understand electricity and pours many yards of concrete.

Naturally, in the peanut gallery that is FB, there are plenty of suggestions on the best way to clean this crusty old item. A gallon of Chemtool. Seafoam. The wire from a bread-wrapper twist tie. Yamalube Carb Cleaner Dip in a Crockpot. Washing soda and a battery charger, what? Hit them with a torch, followed by immersion in ice water? Pine Sol?

The old Z was stored leaning to the right, so that carb got the worst of it. (Joe Gresh photos)

All those might work reasonably well if at all, but when I couldn’t get my XR400 to behave, Chris at MotoGP Werks suggested that cleaning the carb in an ultrasonic bath is the best way to get all those little air and fuel passages well and truly cleared of crud and contamination. He was right, my carburetor looked brand new when it emerged from the tank, and my bike began starting on the 48th kick instead of the 50th. (The problem turned out to be a crap kill switch.)

Anyway, I’m a believer in the ultrasonic cleaner – widely used by jewelers, gunsmiths, etc., to get metal parts super clean without damaging them. It’s scientific. You can find a shop that has one and drop your junk off there to be cleaned for a small fee. OR, you could go to someplace like Harbor Freight or Amazon and pick one up for not that much money.

Harbor Freight’s 2.5-liter ultrasonic contraption goes for $79.95.

BUT! In the ethanol era, it’s possible to get your carburetors squeaky clean and still have your bike not run right. Poor idling, bad throttle response off idle, stumbling off idle – all are symptoms of a jacked-up pilot jet. The pilot jet(s) are the ones through which gas must pass at idle and up to about 1/4 throttle opening; their passages are generally too tiny to even stick a wire in to clean them. Even if you can see daylight through there, the problem, as we learn from our man Chad at Sudco, is this:

“It is not exactly the ethanol, it is a bacteria that feeds on ethanol
that causes all the trouble. That bacteria leaves a film of corrosion
that won’t just rinse or fall off even with carburetor cleaner or an
ultrasonic tank. The pilot jets have such a small orifice that a little
corrosion film can make a big deal. Main (jets) are so much bigger that it
doesn’t seem be such an issue like it is with the pilots.”

Who knew your carburetors could get a bacterial infection? Judging from things like this study researching ethanol eating its way through the steel pipelines used to transport it, it’s a headache that’s way bigger than just us and our carburetors. The only cure is to replace the pilot jets with shiny new ones.

If you like to play with stuff like this, Joe Gresh and Joe Berk have a new blog called Exhaust Notes, where they take on all kinds of projects in their own unique way. Zed’s Not Dead (Part 2) is a good place to start following along in JG’s attempt to resuscitate a decidedly second-hand Z1. Good luck!

John Burns
John Burns

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  • Joe Gresh Joe Gresh on Oct 10, 2018

    Young Mr. burns is spot on about the alcohol. Seems the more I drink the worst those carbs get.

  • Joe Gresh Joe Gresh on Nov 01, 2018

    The carbs are done! I used a lot of Evapo-rust, wire strands from a wire wheel, carb cleaner and a host of small wire brushes.