Motorcycle Repair: carburator, honda shadow 750, car mechanic

Question
Ihave a 1984 honda shadow 750. carba have been overhauled,throttle cable inspected and lubed,choke cable replaced. the problem is that the throttle stays high when shifting up through the gears. it will eventually idle down when comming to a stop carbs have been off twice and the cables are free. it seems the problem is some thing sticking in the carbs. there does not seen to be a vacuum leak. HELP! ps. i'v bee a licenced car mechanic for 17 years so i have some mechanical knowledge, but this has me stumped.

Answer
Hi Gerhard.
 As an automotive mechanic, you will be more familiar with automobile carbs rather than motorcycle carbs so correct me if I am wrong here as I haven't worked on automotive carbs in about twenty years.

 The carbs on a bike are somewhat different from carbs on a car as the feed system on a bike is handled in a somewhat different configuration.
 There are cylinders attached to the needle valve that slide up and down.  Perhaps those are the problem.
 If there is any fuel residue on them that has turned varnishy, then they could stick open or closed (or both).  Either that, or the return springs in that part of the carb are out of spec and need to be replaced.  Thinking about it, I am leaning toward the return springs as the most likely culprit.

Let me know what happens.
Good luck.
FALCON