TOPIC:

My 1973 900 runs great, but, for no apparent reason will rev up to 3000rpm. I'll let the clutch out some to load the engine and it goes down and stays down for quite awhile. Then does it again. I've replaced the manifolds, cleaned the carbs and chacked for vacuum leaks with carb cleaner. Everything seems fine, any help with ideas would really be appreciated.

Im not sure how much expirience you may have, so dont take this as an insult, just starting with the basics... did you check the idle adjustment screw? the one on my 650 would get loose and actually cause the idle to go up, and loading the engine slightly would drop it back down for a short period of time. a little teflon tape on the screw tightened it right up so it would stay in the correct position, and then it was problem free

Are the carbs VM28SC correct for the 73 Z1? Anyway, my first tip would be next time the bike revs on its own, jiggle the choke arm and see if the revs drop. If so, the choke plunger pads are shot. Have a look at my web site for some help. If the revs don't drop when you jiggle the choke arm, then look to the fussy slide linkages... if there is any binding, one pair of slides may be hanging a bit. Pretty common stuff on early Z1 carbs.

I was thinking it could be something with the choke. It revs up to the same rpm as when the choke is on full.

wha if you twist the throtle really quick just alittle and it drops? cable adjustment? thats what mine is doing. i figure its the cables but i'll ask just to be sure. thanks. oh, by the way, later vm28's on a 1977 kz1000.