Hi all, I am having problems making my Ruby engine tick over nicely. All is ok when cold and warming up with some choke applied but once nice and warm with the choke pushed fully in my problems start. If I turn the throttle stop down to get a nice tick over all runs well until I blip the throttle then following this the engine dies. I have had to turn up the throttle screw slightly to increase the revs to stop this cutting out following throttle blips however this makes selecting first gear difficult and always makes a crunching sound. Something that does not occurs with the lower rev tick over.
I have checked for air leaks in the manifold etc and am fairly certain there are none. I have checked and cleaned the carb jets with the exception of the small hidden one (not sure how to clean that one).but no improvement. I have also adjusted the slow running screw but that does not appear to adjust anything so put it back in the position I found it.
Does anybody have any suggestions as to what maybe wrong.
P.s. Prior to all this I checked my ignition timing etc was ok as I was always told to get the ignition correct before touching the carb.

John Mason.

Location: Nottinghamshire

Hi John, I think it likely that your slow running mixture adjustment "does not appear to adjust anything" is relevant to your stated problem. I have PMed you with a useful data sheet for the 26VA. I would check that the slow running and progression jets are clear and that the slow running screw (less than one turn open from the fully screwed down position)has a noticable effect on tickover speed and resiliance.

Ian Mc.

Location: Shropshire

Just picked this up on the Dorset Club site it may be of help.
Austin Seven owners, using the Zenith 26VA carburettor and suffering from poor, erratic engine idling can now improve the situation with very little effort. If you look at the underside of the 26VA you will notice a brass screw head in a raised rib about 30 mm back from the manifold flange. This has always been considered in the past as a blanking screw covering a passageway within the body of the carburettor. This screw plug is, however, an access cover to a jet underneath. Apparently this jet 'bleeds' a small amount of air into the throat of the carburettor when the butterfly flap is fully closed. If you hold up the carburettor and look into the throat from the manifold end you will see two small holes. The furthest one of these is the entrance to the jet which can easily become choked with dirt and leads to the rough idling. It can be reached by taking out the blanking plug and, with a good quality screwdriver which is able to reach far into the hole the jet, can be unscrewed for cleaning. Do use a good screwdriver as the jet is easily damaged You will be amazed the difference cleaning this jet will make. Another useful tip in association with this jet is to have your car ‘gas analysed’ on a Crypton tuner or similar. You will then be able to set the air bleed screw on top of the carburettor accurately. Note the setting by counting the number of turns out of the air screw that gives the accurate setting and always use this setting. Malcolm Watts Cornwall Austin Seven Club

Location: Piddle Valley

The rercent post Zenith 26VA Carburettor might assist.

Location: Auckland, NZ

John,

some months ago I had exactly the same problem... as has been said, the fact that the slow running adjustment does not do anything, is the clue.

The air jet under the carb was blocked. Having removed the blanking plug it was apparent that I would not be able to remove the jet without probable damage, so I used a VERY fine length of copper wire to clear it.

Result was that slow running adjustment worked and I got a nice slow idle.

Chris

Location: Morecambe

Thank you all for your advice. After consulting the exploded diagram of a carburettor kindly sent to me by Ian Macowan I realise I am missing a sealing washer from under the slow running jet. Does anyone know the metric size of the washer as it appears that metric sizes are easier to come by these days.

John Mason

Location: Nottinghamshire

A big thank you for all the advice. My carb has been cleaned all jets cleared including the small jet behind the blanking screw. I now have a nice tick over and a mixture control screw that works. I also had difficulty in trying to remove the small jet behind the blanking screw so managed to clear it without removal using a pressurised can of carburettor cleaner.

John Mason

Location: Nottinghamshire

Location: Shropshire