Small Engines (Lawn Mowers, etc.): Carter carb, proper mixture, needle jet

Question
Hi Ben,  I have a carter carb on a Kohler 301 engine. It will not idle without the choke on.  I have had it apart several times to clean all the holes on the needle jet and such. The tractor sat for 15 years with gas in it so it was a little gummed up.  Could there be some kind of internal clog that I can not access.  High speed runs fine, it just won't idle. I blew it out as much as I could but same results.  Would soaking it in something help?


Thank You

Robb

Answer
ROBB
I would soak the carburetor in a good carburetor cleaner,the idle port is still clogged it is hard to get that open.soak the carb overnight and get a rebuild kit and set the carb at  these settings Apply the initial settings, then start the engine and let it warm up for a couple of minutes. Idle the tractor down to about 1/8 throttle, and then slam it to full throttle. If the main jet is set correctly, it speed right up to full throttle. If it sputters, backfires, and tries to die, the mixture is too lean. If it stumbles and you see black smoke, it's too rich. If it passes that test, run it at full throttle and slowly richen the mixture until you get either an rpm drop, black smoke and rough running, or both; then slowly lean it again until you get an rpm rise. The peak of the rpm rise is the proper mixture. After you've got the main jet set, set the idle speed and mixture so that it runs decent at idle and stays running. Don't lower the idle speed too much, or you'll starve the engine of oil. The manual says 1000 rpm but I like to set mine at 1200 so that the engine gets a bit more lubrication.