Hi everyone,
I have just removed the carb from my kazuma cougar 250, it has always run way rich, even putting in hotter spark plugs didn't help.
The carb is on the bench and it has me a bit confused, I was wondering if anyone knew how to adjust the carb to run leaner, it has a butterfly and also a needle slide thing. I thought this would be a simple job of just moving a circlip or something on the needle but this carb doesnt have one.
The carb is a 'exact' brand.
Any help much appretiated.
Thanks
Liam aka NoMudNoFun

 

Just going by my gut here, without the part number of the carb I'm not going to be much help.

The slide needle is also known as a "variable venturi". The butterfly is the choke, and would only be used for starting the engine cold.

I've only seen adjustable needles on Mikuni carburetors, as a fine tuning method. If that was the original carb that came with the engine, the jets have either oxidized and made the orifice bigger, or someone has damaged the hole by cleaning it with wire, etc.

Remove the carburetor, drain the fuel from the bowl, and remove the bowl. With the carb upside down, and the bowl removed, you should see two posts sticking up from the middle of the carb. One is the "Main" jet (eg, high speed), the other is the "Pilot" (or idle) jet.



Remove the Main and Pilot jet and clean with carb cleaner, the orifice size is stamped on the jet. Without knowing the condition of your jets, I would say replace the Main jet with the size stamped on your existing one. If it still runs rich, go with a smaller size.

Keep in mind that the adjustment screw does not change fuel flow! It only changes how much air bypasses the slide when it is all the way closed. (That's right, only at idle)