High idle when ridden

[Andy novice]

Following head rebuild the bike starts and idles when warm but when I take it on the road the idle revs increase to over 3 thousand revs at idle and stay there until I have let the engine cool down.
No vacuum leaks I can find, nothing sticking and has been synced.
Any ideas?

 

[mrtwowheel]

Check the throttle cable, should be some slack at the throttle and at the carbs, almost sloppy. Are you using the choke to start the bike? Full choke to start the bike and first 1/4 mile, half choke for 2 1/2-3 miles. Set your idle with choke off and engine warmed up. These engines need that choke involvement. These choke cables suck, but, first notch should barely raise the RPMs, second notch should noticeably change RPMs, third notch should raise RPMs to about 1500.

 

[Oscar Meyer]

Mrtwowheel has good suggestions. Also when you had the carbs off did all the carbs move freely when you moved the throttle. If you have a set of vacuum gauges put them on when when the engine has warmed up and see if one carb is off because that will be the one that is hanging up.