Thread: Hesitation with Zenith carby

I have not had this particular symptom, but it does remind me of one I had with mine. I spent a lot of effort trying to fix a hesitation on acceleration. Then I had a breakdown, traced to the coil, which I replaced. The hesitation has disappeared.

The moral is that what seems to be a fuel problem may well be an ignition problem. It could simply be a weak spark for any of the usual reasons (coil, points, condenser, HT leads, plugs etc) or it could be something more specific. For example, when you suddenly close the throttle, manifold pressure will suddenly drop. This means that at this moment the vacuum advance will move, and this could be sticking, or, if the flexible earth link in the distributor is broken, it could be breaking the ignition circuit for a moment.

Hope this helps,

John

Agree with John.
A sticky vacuum advance mechanism could also cause this issue.
full throttle=zero vacuum, low throttle=high vacuum therefore if the transition from zero to high is slowed by a sticky mechanism the timing will be out at some point which may be your "hiccup"
Just a thought. I can't prove it but it is easy to check by taking the dissy off and manually inducing a vacuum (be sucking on a tube connected to the advance mechanism) and watching the setting change.

Phil B