SOHC.co.uk Forums > CB500/550
idle jet differences , 069's
Bryanj:
The 500/550 respond incredibly well to getting the points gap and static timing spot on, this can be very frustrating to do but is worth getting spot on F with a 0.35mm gap
fogrider:
Quite so. Mine ended up at .32mm which gave a dwell of 50%, done static then checked with dwell meter and the strobe and it's all now bang on. Just the carb synch to re-do since having the carbs to bits again. Regarding the timing, the F mark is at 5 deg. Very short for a hemi head. I rotated the backplate until it ticked over best. That was about 12 deg btdc. As that would put max advance too high, I re-set the advance stops to 34 degrees, ( factory worked out at 33). It runs way better bottom end and starts easier. As they are fully advanced at 2500 revs, ( how much time riding less than that ? ) no harm can be done and it goes better, it was an experiment but I'm leaving it like that.
New plugs and a proper air filter should ,hopefully, make the final touches for perfect running.
I still think the sparks are weak, ( pinky /purply ), work in progress, but the improved smoothness makes it much more pleasure to ride.
Bryanj:
As it is put in the trade " they are all like that sir"
fogrider:
That's good to know - I can forget looking for the fat blue thing now !
K2-K6:
Something strange in that you've advanced timing to improve starting. It's an area they are never usually compromised in and notable for just very easy instant starting.
Being a "hemi" or semi-hemi :) as they don't use much piston dome at all, they don't seem to follow convention for that arrangement as recognized by other non Honda applications. If static advance is producing better result then it suggests something isn't quite right as they don't generally need much spark "lead" to run effectively. Have you checked compression yet as that may give more insight.
Giving extra static advance will usually pull up the idle rpm on engines, which has to be countered by having the throttle slides lower to hold onto revs. It may give you an unexpected effect as you go from overun with throttle closed as it pulls raised vacuum against the slides that makes them harder to modulate in that initial phase as you try to bring the throttle back up on entering a corner for example. You could see it just at that point in erratic off on effect.
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