Motorcycle Repair: 1971 cb350 honda, honda cb350, cb350 honda

Question
Bill I have been fighting a carb problem i soaked the carbs for 3 days blowed them out good and put new kits in them and adj the floats. when i started it it ran wide open? what is causing that???? I need help.

                                         Bill

Answer
Soaking carburetors for 3 days should never be necessary. If you were putting them in high-grade carb cleaner you can dissolve some of the parts inside, in extreme cases. Check around the throttle shafts for excessive movement, due to missing shaft bushings/seals.

I hope you cleaned out the emulsion tubes that are stuck way up inside the carb body, behind the primary main jets. They are often overlooked.

http://www.cmsnl.com/honda-cb350-super-sport-350-k0-us_model430/partslist/E++19....    above #19.

Check your floats for pinholes which can cause them to sink and flood.

Make sure that the carburetor slide diaphragms are not torn or have pinholes in them.

This is all background info, as the actual cause of a high-rpm start up condition is one of the following causes:
*Throttle cable mis-routed, causing the throttle arms to be held wide open.
*Throttle valve plates are loosened up from screws backing out of the shafts and jamming against the carb body. These bikes also tend to break the choke flapper springs and swallow the parts.
*Throttle cable is hung up internally at the throttle junction or at the throttle grip. Cable strands can come loose inside the cable sleeve, holding the carb cable open. Replace throttle cables if they look like they are the originals. Check for a small amount of free play when the throttles are adjusted to slow idle.
*Stuck mechanical spark advancer is holding timing into full advance position. Carefully check the spark timing and the condition of the mechanical spark advancer.
*Massive air leak due to damaged carb insulator or O-ring or carbs not seated all the way into the manifolds.

Bill Silver

Look at the throttle arms on each carburetor and watch them as you turn the throttle open and closed. The should move unimpeded back and forth. If you mis-route the cable, when you put the fuel tank back on, it will hold the throttles open in some cases. Verify the throttle action after you install the fuel tank and before you start the engine again.