Strange engine ailment.

[crankedup]

Thought it worth tapping the brains of our resident vintage car enthusiasts. You may recall that I had a mechanical restoration to the Zenith carb on my Bayliss and all was well. However, I am finding that on pressing the accelerator to set off in first gear, that is car under initial load the engine seems to 'hunt' as if the mixture is over rich. This only occurs from set off in first gear and happens if engine is hot or cold and anywhere inbetween. Fuel consumption is still very good at above 35mpg and no smoke from exhaust pipe. Tappets need adjusting causing a little tappity noise but nothing other than minor adjustments. The problem is getting more pronounced now so getting a bit concerned. Any suggestions welcomed.

[215cu]

Mmm... dashpot oil maybe? Sounds like the piston may be moving too quickly to me.

[crankedup]

My car runs with a zenith carb' so no oil pot like the S.U.

[Robin Hood]

Duff condensors have that effect

[Huntsman]

Not got an air leak around the carb or the manifold? Air leak can make them mess about all over the place.

I can put you in touch with a guy that runs a business in vintage carbs.

[crankedup]

Thanks for suggestions, I shall check for air leaks today.

[M3 Mitch]

Frequently ignition problems masquerade as carb problems. I would check over all the ignition components and verify a good strong spark on each plug before adjusting the carb. You need the ignition working right to be able to tune the carb anyway.

On cars that are not driven much, sometimes the battery (accumulator) does not stay in the best shape. When you are at low revs taking off in 1st frequently the electrical system is running more on the battery than on the generator/alternator. This is more pronounced with generators. My FJ 1100 bike was hunting just off idle at creeping speeds, later that summer the battery died. Replaced battery, hunting went away.

[crankedup]

Thanks MJMitch, interesting and I know that my dynamo is not working at the moment due to an oil seal faulty and the brushes get oil covered. As soon as I clean the brushes the dynamo is 100% for 8-10 miles. I do recharge the 6V battery from time to time and try to use the cranking handle to save battery juice. I will put the battery on charge for 24 hours and see how things are then.

[lowdrag]

This sounds remakably like a common Weber problem. I know nothing of Zenith carbs but it sounds to me like either a needle (if they have one similar to an SU) could be worn or the wrong needle or that the idle is wrongly set causing a fuel starvation on accelerating from rest. This is a recurring problem with Webers.

[crankedup]

Yes this is a really odd problem, just had the carb' restored by Burlens and a top class job it is too. Done about a 1000 miles since without problems untill now. I will post up when I have resolved.

[Huntsman]

crankedup said:

Yes this is a really odd problem, just had the carb' restored by Burlens and a top class job it is too. Done about a 1000 miles since without problems untill now. I will post up when I have resolved.

whilst genereally it seems Burlen are highly regarded I have my doubts, I bought a fuel pump from them for the healey, the electronic version that everyone says never fails...it lasted 4 miles.

I took it back, in person as its not far away and stood at the counter while they looked at it, dry solder joint they said.

I was looking in their display cabinet, the quality of the solder on their PCBA was dreadful (am qualified to comment as work in manufacturing electronics).

Odd that it was ok for 1k miles.

hope you get it fixed soon.