After reading suggestions on previous topics on this forum, I have taken out and cleaned the three jets in the body, also the one on the front of the carb, but I still cannot get a tickover.

The engine starts fine and will run higher than tickover. With the air hose off, I can watch the choke flap slightly closed and engine running: as I open the choke flap the engine dies and stops.

The float level seems correctly adjusted.

Am I missing something obvious to others!

Also, while looking down the first venturi with the engine running, should you see petrol dribbling onto the throttle flap from the gubbins half way up the venturi?

Any suggestions greatly received!

Thanks

Think that the jets are still not too clean or that the airways in the carb body are blocked

What state is the insulator block under the carb in? I might be (probably am) wrong but i read that this can cause the symptoms you describe.

have u removed the brass threaded plug at the bottom of the float chamber and used a long slot headed screwdrive to remove the tiny jet within?
its a sod to get out but its to do with tickover i think

Nope. That's the primary main jet, and won't be doing anything when the throttle is closed. The idle jet is the slotted brass 8mm hex head on the front of the carb, next to the fuel filter. The pilot air correction screw is also on the front of the carb, and is made of brass with an offset slot for a screwdriver. I'm afraid I'm not sure what the best starting position for that one is, but you could try winding it outwards a turn or two for starters? Take care not to tighten it up too far, as you can damage the tapered seats. I'd double check all your jets - particularly the idle jet - and then start looking for air leaks, as Joe has suggested...

To check for air leaks either around the block the carb sits on or the inlet manifold to cylinder head join, just spray wd40 directly onto the area and revs will drop......

Thanks for all your suggestions.

I used carb cleaner and blew out the jets. The block looks to be quite new although this engine was standing for several years before I bought it. I wonder if the previous owner had carb problems and started replacing parts. Even the top gasket was newish.


I have put another carb on that was working on a previous engine and it's fine. One small point about this replacement carb is that there is no tickover screw by the throttle.
The engine is ticking over slightly higher than I like: is it possible to use the oftset-headed screw on the front of the carb body to control the tickover speed.

I will dismantle the first carb and double check all the suggestions made, and report back!

PS on two engines I have, the points plate , ie the bob-weights studs, are about parallel to the ground, but on the engine now in the car, the bob-weights studs are vertical!

The engine runs fine: i just wondered the reason for this.

Thanks again for your responses.

Does sound like an 'Air Issue' although it might be worth checking the fuel filter as it may have a little bit of sh**e in it

Ok rather than guessing and making stuff up ....

clean the jets as you have done make sure the idle jet- ( the 8mm hex external one ) is screwed back in tight and hasn't fallen out! edit(make sure the choke pull off device is still there or has been blanked off)
Next set the timing and the tappets as you may have trouble getting it to idle if its set up wrong .

Get it started and running as slow as it can ( you can use the choke as it only opens the throttle in the first 1/3 or so of its movement) then spray petrol or brake cleaner around the base of the carb and the manifold to head inlet joints - any change in revs you have an air leak which needs sorting.

then you need to set the idle mixture and the tickover speed. The speed is done with a screw ( underneath and held in to a spring thing) or knurley head thats obvious on the actual butterfly lingkage of the throttle, the mixture is the offset slotted jet in the front of the carb by the brass jet


co2jet by Sean602, on Flickr

start by screwing the jet out by 1/2 a turn at a time untill the revs start to rise, if screwing out makes things worse then screw it in untill you can get a stable idle - you may have to find the sweet spot first if its been badly set and causing the problem. There are no "factory setting" of this jet but you can screw it fully in -GENTLY- as it can damage the seat and the jet, then back off between 4 and 6 turns

once you have a stable idle reduce the idle speed with the linkage screw till your about 900rpm

Fine tuning of the idle is tun screw out untill you get a slight rise in your tickover , then screw it back in slowly to the point where the engine begins to falter, then back out by 1/2 to 1 turn and re set the speed.

if it falters slightly on opening the throttle give it a further 1/2 turn to enrichen it.

none of the above will be easy if the ignition or the tappets are out or if there is any leaks in the inlet or if you've added crappy "improved performace" filters or inlets. So make sure the mechanicals are spot on. Follow the procedure you may have to do it more than once as each time you go through the process it gets a bit closer to optimal , just jumping in and fiddling can get the whole thing seriously out of kilter and leaves you in a mess.

ah see youve gone down the substitution route - still worth setting the idle mixture or "C02 level" as above having a tickover to start makes things a bit easier.

the points carrier rotates as its on the camshaft it will depend on where the engine comes to rest when switched off