Thanks all, lots of good tips for tomorrow, Sunday means quiet in this part of Germany! Backplate original, float heights and float mass checked during rebuild, everything present, in good condition and tight / correctly fitted. Was too late last night to run the bike and so check for leaks using carb / brake cleaner, neighbours living room joins my garage! Earlier in day I had packed out backplate by 2mm using 6mm washers, fiddly job, and now she ticks over and balances, idle mixture screws all between 1,5-2,0 turns out. Still the tip of the domed adjuster screw is only just touching down on the lowest corner of the idle stop plate (what do we call that thing?), but at least I can now set an idle of 900-1100rpm. So I still suspect my slide cables are short, has anyone got an original cable they can measure?
Idle is though not perfect, RH carb is definitely coughing back and I am not convinced that middle choke is properly seating so will continue with checks for air leaks.
two things missing in the above: Choke sliders need to close fully and all three equally. and no word about the float settings yet, I would check them, too.
For me it looks like the idle adjustment screw is at it's bottom end and if still the idle is beyond 2.000, the beast either get's to much gas (choke sliders, float settings) or - as already mentioned above - to much air (airleak).
also check with a 100 % straight piece of metal that the carbs are all correctly and the whole thing is not bent. This happens very easily when you push the carbs onto it's seats (be it the rubber connectors or the teflon isolated alloy manifolds).
I install the carbs individually and then attach front and back plates, but don't check flat across all three carbs front or back. Front and rear plates are oem parts. Following your comment I checked flatness and no not flat. I suspect that it was this that resulted in not being able to set an idle under 2000rpm this time around, whereas before this carb overhaul could get 1100rpm, essentially luck. Further checks:
- Centre choke piston hanging up due to cable protruding through nipple pushing nipple to one side so fouling in the choke bore
- Filed protrusion back , now ok, but again aftermarket cables not up to scratch, recently had to make my own speedo cable
- Probably be making all my own cables in future, but to do that in most cases first need access to originals
- I am running billet inlet stubs, originals fractured at lower mounts about a year back (3000 miles)
- Isolating bush is 1 original (centre), 2 a plain bush (with axial od groove) and rubber 'gasket' - see photo
- Rubber gaskets are not seating properly tending to pop into the inlet when carb pressed fully home
- Found billet stubs to be 1mm shorter than original cast items!!!
- Original isolating bush also not fully seating, but is sealing
- Today have not been able to get a good install of gaskets over numerous attempts
- No point in trying to complete install and check flat across all three carbs, will just end up going around in circles with flat / not flat and gasket popped out / not, idle good / not
- Conclusion, okay running for past year (3000 miles) was basically down to luck, L ring usually deforms so not effecting a proper seal against air ingress along groove of bush!
Tomorrow will take 1mm off isolating bushes, have 2 old (original), 3 new with L rings and try again, carrying out air leak tests. Should work.
Where can I buy inlet stubs, ideally billet to original dimensions and does anyone know of a reasonably priced source for original type isolating bushes? Ideally need all parts by mid this week so that I can ride the beast to Breganze for the 75th.
This setup has worked in the past, idle as intended.
Thanks, exactly how mine was prior carb overhaul 8000miles ago, witness marks on idle stop plate to prove, but since then not so.
