Starting and running issues

[Peter E.M]

Hi I have a 1965 24tfs with a 36A engine. It has had a rebore new main bearings new piston rings crankshaft seals and electrex world electronic ignition fitted. . It has a 140 main jet. I can't get it to run from cold without a spray of break cleaner, once it is hot it will start ok without it but it has to be hot. The engine takes a time for the revs to die down when revved up and it is difficult to get it to idle. I have spent a lot of time on it and am stumped to be honest. Any advice ( of a helpful nature) would be greatly appreciated as I would like to take it to a trials meet.

[tonyed27]

Sounds like carburetor problem to me.
Check ALL the jets to eliminate blockage from pilot jet.
The 'run on' sounds like the slide hanging up. Check condition of the throttle cable for snagging, make sure the slide closes completely.
check the float level.

[Peter E.M]

Ok I will do as you recommend and see what happens. Any idea of float height.

[tonyed27]

It depends on what carburetor it is. Go online and see if there is a download for your carb or wait until a more knowledgeable member of these answers. Normally it is about horizontal.

[IanCordes]

It could have an air leak on the carb inlet, which would of course mess up the mixture, and could well be the cause of it not wanting to shut off. What carb is fitted? If it is the standard Villiers S25/6, there is no throttle stop, so they were not designed to idle, unless you hang the slide off the cable. There is a mod which can be done, but that is not the answer to the current issues.

[John Wakefield]

As a matter of interest here is the list of the various S25 carb configurations:
S25 Standard body, fitted to all engines
S25/1 Standard body, fitted with separate cable operated choke mechanism when used on Bond Mini cars with 9E & 31A engines
S25/2 Standard body,fitted with choke slide operated by a rod 32A(road) and 37A engines
S25/3 Standard body fitted with a choke slide operated by a cable & handlebar lever. 3T, 9E and 31A road engines
S25/4 Industrial use
S25/5 Bored out to 1" choke, no choke slide. 32A engines
S25/6 Bored out to 1" choke, fitted with choke slide operated by a rod. 32A & Starmaker engines
S25.7 Standard body, drilled to accept throttle stop. Bond Mini cars and varied road engines
S25/8 Standard body, drilled to accept throttle stop. fitted with choke slide operated by a cable and handlebar mounted lever. Bond Mini cars and varied road engines.

[John Pattinson]

I use, float height 1/4" from float to rim of float chamber and no probs..S25 Villiers.

[John Wakefield]

Sounds like carburetor problem to me.
Check ALL the jets to eliminate blockage from pilot jet.
The 'run on' sounds like the slide hanging up. Check condition of the throttle cable for snagging, make sure the slide closes completely.
check the float level.

Looks like there is not enough free play on the throttle cable, the trials TFS was not set up with a tickover, with no throttle stop screw. Setting the tickover on the throttle cable is not a good idea as with the turning of handle bars the tension on cable will vary and speed of engine increase. If you want a tickover best to source a S25/7 or /8 carb body or drill out and tap the existing body to fit an idle screw. The indent of the hole is cast into body so easy to drill and tap. Not sure what the thread is (probably BA) but same as the mixture screw. You will then need to source the screw and spring, and the throttle slide will need a small chamfer filing for the screw to mate to. Villiers Services should be able to supply the screw (part number V1948E) and the spring (V749E) the slide with cutaway for screw is V1308E

[IanCordes]

We don't know what carb is on it yet, because Peter hasn't replied to tell us! It could be a Concentric for all we know. Many changed to them from the S25, stub to flange manifold conversions being readily available.

[iansoady]

Looks like there is not enough free play on the throttle cable, the trials TFS was not set up with a tickover, with no throttle stop screw. Setting the tickover on the throttle cable is not a good idea as with the turning of handle bars the tension on cable will vary and speed of engine increase. If you want a tickover best to source a S25/7 or /8 carb body or drill out and tap the existing body to fit an idle screw. The indent of the hole is cast into body so easy to drill and tap. Not sure what the thread is (probably BA) but same as the mixture screw. You will then need to source the screw and spring, and the throttle slide will need a small chamfer filing for the screw to mate to. Villiers Services should be able to supply the screw (part number V1948E) and the spring (V749E) the slide with cutaway for screw is V1308E

I modified the S25 carb on the Francis-Barnett I misguidedly restored a couple of years ago and felt it was worth while. I have the photos somewhere I think....

[garybam4711]

Sure it’s amal as remember speaking at Telford?

[Peter E.M]

Hi the carb is an Amal 626. With R302 stamped under the 626

[Peter E.M]

Concentric I believe

[IanCordes]

Maybe it is not a 2-stroke one?

[John Wakefield]

Maybe it is not a 2-stroke one?

According to the Amal spec 302 indicates a 2 stroke set up https://amalcarb.co.uk/choosing-the-right-carburetter The notes on rebuilding a Mk1 Concentric may be helpful https://amalcarb.co.uk/rebuilding-ma...ic-carburetter Might be worth checking the carb flange for distortion as air may be leaking in there, check also that the 'O' ring is in place and in good condition.