Motorcycle Repair: Honda CB650C 1981 Carb, bench test, corrosion problems

Question
I have a problem with my carbs, when my engine is off they are fine but after they have been running for a minute they start to leak out of the overflow.  I have already cleaned the carbs once already and all the parts are original.  Any advice would be appreciated.

Answer
If the bike has a vacuum shutoff, then fuel only flows when there is a vacuum on the inlet side; i.e. when the engine is being started or running.  Check the standpipes in the carb bowls, they can have pinhole corrosion problems and will let gas out even though the float and needles are working fine...  Otherwise you may have to re-clean the needle valves and seats.  It is always worth doing a bench test before putting the carbs back on.

Good luck,  Jan