How-To Guide: Cleaning a Motorcycle’s Gummed Up Carburetor

How-To Guide: Cleaning a Motorcycle’s Gummed Up Carburetor

Customer question:

My motorcycle has been sitting for about 9 months. It starts fine. However, when turning the throttle, it sometimes hesitates and almost dies.
What would the best method be to try and treat this?

motorcycle hesitates and almost dies - gummed up carburetor

First, check the condition of the gasoline.

Investigate the gasoline in the tank. If it’s 9 months old, the fuel has likely gone bad.

In order to make the determination, you might compare the clarity, color, and smell alongside fresh gasoline.

  • ∙ By clarity, we mean that it should be crystal clear. Any haze, sediment, or precipitate is undesirable.
  • ∙ For color, it may have a slightly different hue. However, it should still be light, like a straw yellow.
  • ∙ For smell, you’re hoping for a similar odor profile. But as you check, be careful to not over-sniff. All varieties of gasoline contain many hazardous components — nearly all of which are quite volatile. If you find that it has gone bad, then please read on to the next section.


Next, remove the old fuel from the tank.

In need of restoring your fuel system, you’ll want to drain as much of the base gasoline as you can.

If it is at all possible to remove the tank, do so. Then add a few ounces of Berryman® B-12 Chemtool® to it. Carefully swirl it around.

WARNING: It is important to be cautious with part #0116 if you’re fond of your paint! The beloved H.E.S.T.  product can ruin most finishes.

Drain the B-12/bad gas blend, repeat until clear, and reinstall the tank.

Now it’s time to add a Berryman® fuel additive.

At this point, we’d recommend using a top-quality fuel additive to thoroughly clean the fuel line, carburetor (internally and externally), intake valve(s), and combustion chamber. Add B-12 Chemtool® Total Fuel System Clean-Up at 1 oz/gal and top off with fresh gasoline.

If your gas tank is fairly small, you should run the #2616 in back-to-back tanks.

Finally, inspect and clean your carburetor.

The easiest way to clean the carburetor is to remove the air filter and spray our B-12 Chemtool® aerosol (part #0117) directly into it.

Assuming that the carburetor hasn’t corroded internally—that can happen with aluminum carburetors that sit too long with ethanol-based gasoline like “E10” in them—then that should quickly help smooth out the idle and improve runability. You can, of course, start with this step, but doing so may only temporarily mask bigger issues.

All done!

Once you’ve completed this 4-step regimen, you can be confident in your healthy fuel system, again.

However, if you plan on letting your bike sit for extended periods of time again, you’ll need to make sure that the gasoline is protected. Adding a fuel stabilizer to the gas tank and topping it off with fresh fuel will accomplish this.

Best of luck!

Berryman Products