Club 80-90 Forums

Thanks for your reply ajsimmo - yes sorry I got the names mixed up (for some reason I have a mental block around "advancing" leading to "before"). But anyway I think that advance signal (the one I took off in the vid) should not be present/changing the timing at idle, right?

Yep, engine was warm and choke completely off when I took the timing figures, and I had blipped the throttle to get revs down. I found:

A + R vac pipes both connected - 20deg BTDC
R pipe only connected - 5deg ATDC
neither connected - 7deg BTDC

The timing at the distributor has not been touched since you set it a few months back Andrew.

...so I guess this is all consistent with the problem being an inappropriate vaccuum at idle coming through the advance vac pipe.. presumably due to the throttle being held open as you and bigherb have suggested.

I will try and look into what is happening with the throttle plate and check the choke housing/linkages as suggested.

Will be Thursday before I get any more time to tinker... darned day job!

Thanks again.

ps I love the fact that I can now make vague sense of the conversation above when 18 months ago I didn't know a carburettor from a catalytic converter... - the joys of van ownership!

Time for an update...I found that both carbs (especially the left) were reluctant to return fully to the throttle stop position where the screw hits the body, even with choke fully off - which would explain the vaccuum signal at "idle". So bit the bullet and took both carbs off the van to investigate. They were a bit gunked up especially around the ends of the throttle spindle, and the accelerator pump arm. Cleaned them up and now the springs return the throttles home nice and lively. Set up the throttle gaps following sarran's excellent video.

While off the van I thought I would check the float needle valves and float level... the needle valves are operating fine but I'm not sure if the level is low. The only info I could find on correct float level was on the ratwell site (http://www.ratwell.com/technical/DualCarbs.html" onclick="window.open(this.href);return false;) stating that the height should be 12-14mm below the top of the lower body. Mine is stopping at more like 18-19mm below on both sides.

Can anyone confirm if the 12-14 figure is correct? (Even better anyone have the Bentley pages that cover these carbs - must be in one of the Bay manuals I think as not covered in the T25 one...). And should I worry about the low level? It must have been set like this for some time. I'm not sure how to raise the level by 5mm - ratwell used a thicker gasket to raise the level but that would be 5-6mm thick gasket material - seems awfully thick?

To wrap this up - my dodgy idle/stalling seems to have resolved now. It was probably a combination of problems; I found a few things and did various bits after taking the carbs off, including:

- carb throttle was not springing back - cleaned up gunk and replaced the springs
- reset the throttle plate gap
- replaced both needle valves, one was decidedly sticky
- blew through jets and general clean up of carbs
- replaced the metal gaskets inlet manifold-to-head, and also the gaskets manifold-to-carb which were practically non-existent
- replaced a dodgy looking joint where the vaccuum retard signal comes from

So I think a combination of the throttles not closing properly leading to imbalance and retarded timing at "idle", and possibly some air inleakage.

Several test drives and so far, no stalls and it seems stable at idle, and driving well. Hooray!

Thanks to bigherb and ajsimmo for the help in this thread!