View Full Version : ZS carb tuning

06-17-2004, 01:25 AM
I'm uncertain about the tuning of my ZS carb. I'll go to a weber DGV at some point soon, but for now I want to keep this one running right. Anyway, i've noticed that when i turn the vehicle off, it doesn't turn off imediately and it sort of klunks three or four times before coming to a complete stop. wondering if it's running lean and causing too much heat (and thus sort of a glow plug effect) or do I have other issues? I've got some noise during start up, and a little less so during operation too BTW, I'm assuming it's rod bearings or something (see one of my many other threads for the night). Am I on the right track here?
Thanks /ubbthreads/images/graemlins/cheers.gif
Rob "I'm going to get my 50 dumbest questions out of the way" Selina

06-17-2004, 03:33 AM
Hello Rob,
why change to a Weber?, the Zeniths are fine and need little attention. They are not difficult to set up, and once done do not need constant attention; it seems quite common for people to automatically (unjustly) blame the carburettors when the car doesn't run too well.
Running on can be due to a weak mixture, timing, build up of carbon even too high an idling speed. Initially give the car a tune up.
You may like to consider fitting a screw on oil filter conversion as this retains the oil so that on start up you don't have a lag while the oil pressure builds up.

Alec /ubbthreads/images/graemlins/thirsty.gif

06-17-2004, 07:33 AM
I agree with Alec. Why change to to a DGV?
If your only real complaint is the poor-shut off, a common cause is high idle speed (as Alec has stated). These carbs also have a large rubber diagphram (under the sliding piston) that can crack with time, and cause poor running.
A nice (and correct-looking) modification is to use the twin-carb manifold and SUs that are used on European and Canadian cars. You can see them for sale on EBay.

06-17-2004, 09:46 AM
My GT6 did the same thing, run-on, or "dieseled" after the ignition was cut off. I did a complete tune-up, still happened.

Finally, I was told that my idle was set too high. It was idling at about 1100 RPM. When I reduced the idle RPM to about 800, it stopped dieseling!

However, it does diesel once in a while, maybe one in ten times when the engine is turned off, and not much then. I just depress the clutch and let it out to stop the engine.

Works great no one notices. Maybe if Dave Vizard or Kas Kastner is ever in my neighborhood they'll come by and take a look at it?

Dave, Kas, plan any trips to VA anytime soon??

06-17-2004, 11:26 AM
thanks guys. main motivation for the webber is a little more power, but it's a low priority...this car can get me in enough trouble stock /ubbthreads/images/graemlins/grin.gif Might have to reconsider my plans there.... /ubbthreads/images/graemlins/england.gif
As for idle, it's at 800rpm, car runs pretty good once warm, no real carb issues aside from the dieseling. The knocking on startup and shutdown bothers me. it's a loud clunk. it does it about two times on startup, and about three or four on shutdown....

06-17-2004, 12:22 PM
The knocking on startup and shutdown bothers me. it's a loud clunk. it does it about two times on startup, and about three or four on shutdown....

May want to check your ignition timing. Also, see if anything is loose and banging around on the engine (such as the air filter, alternator, etc.). I hope it's not a mechanical problem, such as rod bearings.