Z1OwnersClub GB

Hi all
Does anybody know what causes the rev to not drop as quick as they should? When I blip the throttle it’s sometimes slow to come back down to idle !
Any help would be much appreciated.(1979z1000st)

Possibly cracked rubbers between carbs and head. Is the throttle snapping shut all the way.

Blocked pilot jets are typical. I always drain my carbs after every run as I never know when I'm going out next on the bike. Ethanol, say no more.
Paul

Mixture settings. Use a Gunston Colortune Plug to set.

Synchronization. Use vacuum gauges.

Choke Plunger Rubbers. Have them replaced with Viton type.

Hello mate;

Had something similar on mine after a carb rebuild. Turned out to be lean running, a bit of tweaking of the air screws sorted out the idle mixture and cured the problem. (79 Z1R in this case).

TTFN Grog

Thanks for all the replies, the bike has just had the carbs rebuilt , so maybe a bit of fine tuning , is there a way of setting tgg HD e air screws without gauges? Ie so many turns out ?

Binding or incorrectly routed throttle cable?

Found the same thing with incorrectly adjusted throttle cables

Assuming the throttle cables are free running and there are no air leaks, there's a decent chance the carbs just need setting up after the rebuild (which fingers crossed should also mean the pilot jets are in decent nick). I think the ST has 28mm carbs, yes? In which case, turn the air screws fully in and then back them out one and a half turns as a good starting point, see if that helps. The further out you back the screws the leaner the mixture, so if the problem persists try turning them back in an eighth of a turn at a time, see if that cures it. Without gauges it's a bit 'finger in the air' for accuracy but hopefully it'll tune out the hanging problem.

TTFN Grog

if the carb to head rubbers are drawing air and causing the revs to hang when you shut off, you can check by spraying a but of easy start around the rubbers when the engine's idling. If the revs rise as you spray 1 rubber, its leaking

Hi, just put the carbs back on after getting rob to put new seals on the choke plungers , started first time and all seems ok , but number 3 down pipe doesn’t seem anywhere near as hot as the other three ? Spark is good, also does anyone have a simple plan of the connection and route of all the vacuum pipes as I’m slightly confused what goes where !

Hi Foxy

there's only one vacuum pipe on the carbs.
It goes from the n°3 carb to the fuel tap in order to open it.
If you don't have a vacuum fuel tap, you have to block it so the n° 3 cylinder isn't overheating due to the poor mixture.
The other two pipes on the carbs aren't going anywhere, they only serve to let air in and out of the carbs . You can put the ends of the pipes under the seat and downwards to avoid water getting in .
GrtZ
Philippe

Thanks for all replies and happy new year to all .