by dickfaber » Tue May 14, 2013 9:10 am
this may help (or maybe not)
when the throttle shafts wear, they allow small but significant air leaks, and also mean the throttle plates sometimes dont shut completely. when this carby is a cv style (reliant on mainfold vacuum signal for slide/needle fuel delivery) it causes all sorts of issues; just like the ones you describe.
i learned this from my days stuffing around with gpx250
solution (probably not the best, but it was the most effective) - machined the throttle shaft to a common fulll size, reamed the carby body throttle shaft hole to a common full size; ensuring it was actually round. then machined some nylon to the appropriate sizes and fitted them. instant sucess!
point is, check the slop in the throttle shafts at the carby. at idle, give them a strong wiggle and see if idle changes, and give them a squirt of wd to see if that changes idle quality
I am a bilingual illiterate; i can't read or write in two different languages