91 kat 750 carbs racing

[tujungaman]

Hey guys.. i have a 91 carb set that races and will not idle..

When i plug up the carb "t's" on the upper part of the carbs "vent tubes' the engine will idle then dies.. So were do i go go from here..

i have rebuilt the carbs
o rings on intakes
replaced o rings under the sync plugs
new o rings through out
new needles
new diaphragms

This bike i got for free is pissing me off..

[GaryS-NJ]

I bought a not running bike and unstuck the carbs and had the same problem. Ultimately I swapped the carb bodies concluding that it was most likely mangled choke plungers or the choke plunger orifices in the carb bodies (the chokes were corroded/seized in also).

Did your bike ever run? did you do a bench sync? are you sure the throttle plates are fully closed when you are trying to idle (idle knob backed off and slack in throttle cable)? Did you check for air leaks? Did you mangle the choke plungers..

[maniac1886]

Sounds like they are out of sync

[tujungaman]

i did check for leaks.. over and over again... the idle like i said will go down when i but my finger over the 1/2 carb vent "T".. The idle comes down.. those "T's" should not have any vacuum on them.. I haven't taken the choke apart..So I have know idea if they are bad..
i haven't sync yet..

[GaryS-NJ]

carb vent tubes

when you plug the vent tubes, you might keep the bowls from filling and/or the carbs from sucking fuel from the bowls. I would call this a red herring and disreguard. Your high idle is typically an air leak (intake manifold orings typical) but possibly a leaking choke circuit (this assumes you ruled out the obvious of the idle screw engaged too much or the throttle cable pulling). Mine was idling at 3000 rpm due to fuel leaking by the choke/enrichment with the choke closed and all choke plungers seated, and I could open the choke and get it to idle even higher.. Did you resolve this??