poor idle

Stephen Baraboo /

so i've been having trouble with the idle on my '79 columbia commuter. it idles fine when on the kickstand, but stalls if the back tire stops spinning (like at a complete stop). of course, i've tried adjusting the idle screw, but no setting works. the other day i took off the air filter and tried stopping at it idled fine and didn't stall. what does this mean? i think i need a new air filter anyway, but does this point to anything else wrong with the air flow in the engine? are there performance air filters i should try?


Re: poor idle

It means not enough air is getting into the carb. Try poking some holes in the sponge inside the filter. Or replace with a softer, newer, thinner sponge to enable more air flow.

Re: poor idle

Or you might have a bad connection between the carb to intake or intake to cyl. inleaking extra air and robbing power.

don-ohio (:^D

Re: poor idle

Ben Van Zoest /

If she idles ok w/h the air filter yes you do have a clogged filter but the filter should last a very long time. My Columbia

gave me fits until I bored out the jet with the appropriate drill size. Behaved perfectly after, actually ran a bit faster too.

Either air or fuel problem both easy to fix.

Re: poor idle

It may be running rich. you may need to replace the fuel inlet needle or the float may be going bad. If the fuel rises in the bowl then you will draw more fuel into the engine. This will cause you to raise the idle up to allow more air to lean out the mixture. This will cause you rear wheel to spin but that means your clutch is engaging, so you play with the idle to where it will run at the lowest tire spin. When the wheel hits the ground the engine has a load and it causes the engine to slow. This means it has less need for air and it becomes to rich and stalls. When you remove the air filter you remove the restriction of the filter. This creates a leaner condition and it runs.

Just something to check. If it is running rich it will continue to get worse and you will start to see fuel dripping from the carb.

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