Z1OwnersClub GB

Does anyone know how to set the twistgrip tension on a May 1975 Z1-B? My shop manual (revision 3, July 15, 1974) shows a tensioner screw underneath the switch body. My switch body (which is the original fitted to the bike when new) doesn't have one! There's also no mention of any alternative procedure in the supplement. The problem atm is that the throttle slides are crawling back to rest position with the cables attached. Without the cables attached the slides snap back immediately. There are no kinks in the cables and I can operate the twistgrip by pulling the cable nipples. Any ideas?

Sounds like you need a bit more slack in the cables,
If there is no slack the throttle action will act as you describe and not quickly close.

As Rob says, slacken the "push" cable a little.

Yup agree with slacken push cable. Suggest trying action with push cable removed from bottom pulley with engine not running and carbs should all snap back nicely. Then re-attatch push cable and adjust accordingly. Hope it goes well

Following you guys advice, I took off the cables and oiled them just for the hell of it (well that's what we used to do 50 years ago). I also cleaned out all the bearing grease I'd previously put in the cable channels in the twistgrip thinking it would make it smoother and keep out water. I then screwed up every single adjuster to within an inch of its life and checked the throttle action with the carbs sitting on the seat and just the pull cable in position. Voila! Snappy throttle closure! Then tried it with the push cable and once again the throttles snapped shut. Brilliant job and many thanks to all you guys who offered advice. I would have proceeded to refit the carbs and cables had I not hit another bloody issue whilst refitting the front sprocket/clutch pushrod cover (see "Backward Bolt?", showing in this theatre today).