I know this has been covered a million times, but I tried the search function and couldn't find it.

I'm messing around with one of them little 602 things, and need reminding how to do the dynamic timing, I know the procedure, and have the static timing point marked but can't remember the number of teeth for total advance. I've got a great write up explaining the whole thing, printed out and shoved in a Haynes manual, but I can't find it at the moment. A link to where I might have found that write up would be great.

Secondly the carb, it's flatly refusing to idle. I've checked and blown out the external jet on the front, the adjustable needle thing, and all the drillings associated with them. Anything I might have missed? And I know Sean's linked to a guide for twiddling the screws, from a vw forum, where was that again assuming it's what I should use to get things right?

I've done the valve clearances to 0.25

round 7 teeth.
its on youtube for the "Tuning the solex..."

tappets 0.25, points 0.4 plugs 0.6 timing to the peg 8* and itll start and run after that its tuning

It starts OK, static timing's OK, but it won't even think about idling, dies as soon as you lift off the throttle. Had a slightly cracked carb insulator, and when the new one gets here I'll put the freshly cleaned carb back and see if it's any better.

When following that video, how does one set the revs without a tacho, is by ear good enough?

spose itll have to be...any iphone apps for that? lol

Ok so it's still no better. Tappets are right, timing's right, the carb's been off and cleaned, including bowing through all the jets especially the idle circuit. It appears to be in good shape with only minimal wear on the moving bits. It's been refitted on top of a new insulator block and gaskets.

The engine fires up reasonable easily with choke and some throttle, and will sit at a fast idle until it's warmed up. However when I try and put the choke in it won't have it. Pushing the choke in to about 1/3 - 1/4, so that the butterfly is mostly open, but the idle is still increased, the revs drop to around 1500 - 2000 at which point it starts faltering. With the filter to carb rubber off, placing 2 fingers across the primary choke picks the revs up considerably, as does prodding the accelerator pump lever. So I'm quite sure that the problem is weak idle mixture, but I've checked and cleaned the jets and drillings, and no amount of winding out the volume screw makes any difference.

It's got a brand new insulator block and gaskets, and I've checked the inlet to head bolts are all tight, so I'm reasonably sure its not getting 'false air'.

Now the most telling thing is that I've tried another carburetor, a manky looking thing with considerable wear and missing springs, and it fixed the problem! I can push the choke fully in and it idles at about 800 exactly as it should.

So the problem is definitely the carb, and I'm very sure it's a lean idle mixture, but what might be causing it? Thinking about it I didn't check the float height, and the accelerator pump diaphragm is a little bit weepy, could either of those be the problem?
(Sorry that's so long, but I do like to be clear!)

Joolz,
is the secondary butterfly closing fully?
If not, 'false air' leaking past it would give the symptoms you describe.
Correct sealing can be checked by pouring some engine oil into the secondary barrel with the engine on tickover.
The oil should sit on top of the butterfly, at least until the throttle is opened and the smokescreen released...

https://www.flickr.com/photos/30132857@ ... ist-9vX9e9

It appears so Ken, from a visual inspection of the removed carb. And the anti tamper cover is still in place on the adjustable stop screw.

Time to do some tampering, in that case...

Maybe silly question/point, but are you sure you haven't got your idle/CO screw fully turned in? It is that screw at the front of the carb with the ofset turn grove/slot in it.

Yep sure, it was about 2 1/2 turns out to start with, and winding it in or out didn't help.