Motorcycle Repair: 1981 honda cb750k, 1981 honda cb750k, cold weather

Question
ok here goes. problems are as follows- bike will not idle without choke on , runs descent with hoke on at low rpm but will not rev very high. wont run at all without choke on.put in new accelerator pump and air cut off. both were torn. thought that would fix it-negative. cant seem to find a vaccume leak anywhere then i realize that there is a vaccume unit in case you forget to shut off the petcock. thought it was sucking air through there so i hooked it back up instead of bypassing it or plugging it off. the same results occur. carbs are synced up near perfect.seems like it is lean at high rpm and cant even ride it without the choke on?????????timing advance unit? the only mechanical mods are factory air box removed and replaced by single filters.ran the same before the filter change.seems like a vacume leak or lack of fuel at high rpm. almost like a rev limiter!

Answer
The low speed circuit is plugged up.  You need to pull the carbs and clean out the idle jets.  I'm pretty sure the choke has a fast idle cam on it so when the choke is applied the idle speed is kicked up to make the engine idle faster for cold weather.  Running without the factor air box will lean the mid-range and top end out so you may still need to rejet the carbs too but the reason it won't run without the the choke is due to the plugged idle jets.

Regards
Rich