well it ain't the carb! - quite cold here in England this evening, but despite that, and only having one hand at the moment, I couldn't resist trying a second carb I picked up recently. It was quite difficult overhauling as you can imagine - put carb body between knees to undo/do up screws and jets! so I will try and forgive myself for overlooking accelerator pump circuit in full anyway, persevered with the churning and even checked spark - a lovely fat one now, and then I hit the sweet spot and it was trying every time again bless it's heart. Symptoms almost identical, but kickback everytime now.. ran on 3 occasions for 2 to 10 seconds.. ah well, time for another regrouping session. My 900 almost got a little sister yesterday - a 1989/1990 750SS came up on UK Ebay, hardly needed anything and low mileage - went for £780 approx.

Have you checked for good compression?

Yes I have Higgy, but I guess that will be my next thorough port of call now... not that it was too low, but wonder about the opposite. My compression tester is quite old now but I don't see any reason to doubt it. I think it was around 130 p.s.i. and I remember being pleased that it was even. I might do a short wet test with a 2nd low capacity battery linked up to see how high it gets with a decent cranking speed. (both plugs will be out of course). Something you could help with maybe Higgy as I see you are a Weber lover (me too! - I have 3 of these brand new (42) ready for a project) :- I notice that 'they' (Cagiva) played around with the air intake/ram height as the spare carb, off another Paso or SS of similar year, had shorter studs so plastic spacer omitted intentionally - unless this was the difference between 750 set-up and 900? You mention that one of the crucial mods is to obtain and fit the longer auxiliary venturis, I have the shorter ones at present so maybe something for the future (when/if it ever runs properly!)

Think i've finally cracked it.. stumbled on a long thread where some other poor sufferer has been trying for ages to solve identical problem also with a 900 - has Kokusan as std but just fitted High Comp pistons. answer was to retard static by 2 deg (I know graph starts at zero advance) and it worked. I'm scratching my head as to how to achieve same with single timing sensor without heavy machining but it looks like my only simplechoice is to convert to Kokusan to achieve same. I will peer into spark plug hole to try and confirm pistons maybe.

Thanks Higgy Both carbs are 44 and I will wait a while before even looking at jet sizes etc - baseline is a good place to start until I learn what pistons are fitted etc. I appreciate the theory behind varying intake stack height, I remember when Ferrari/Fiat introduced variable tract length on road cars and F1, was doing some consultancy work for a couple of teams at the time - what i wanted to know was, does the 'spacer fitted' set-up on a 900 actually show a worthwhile improvement in terms of performance or tractability or both?

Kokusan it is.. for this cure, when I am well enough. Will pick up this thread in a couple of months all being well. Thanks again everyone

3 ohm coils from Dyna, Andrews etc are just fine, nothing will happen. Every Duc shop or parts supplier sells them.
The only ones that are known to sometimes cause damage are the ones from Nology as their 3 ohm coils vary and some actually have a lower resistance.
I did run 2,7ohm coils from Silent Hektik for many years with the original Kokusan units although I wouldn`t recommend anyone to do so as these should only be used with their own programmable CDI unit. Still, I personally never had a problem.
the 3ohm Andrews coils are the yellow ones if I remember well.

G.