Hi all and thanks for the add. I had no idea this forum existed but hopefully someone can shed some light on this problem.
93 4BL DTR with 3 wire servo, cycles open-closed-open OK when turning on ignition but doesn't close when engine is started (I believe it should do this and then open as the rpm increases as in the YouTube vid).
Black/yellow signal wire was disconnected and isolated when I got the bike this week, I've plugged it back in and it makes no difference. Bike sounds good at 6k rpm+ tbh, revs out OK but at low revs it sounds weak and reminds me of the one I owned 25+ years ago with the powervalve fixed open (which is effectively what this is atm).
Has anyone ever measured the voltage through the black/yellow signal wire from the CDI unit? At cranking speed I'm getting up to 19v which would suggest the CDI works OK and it's maybe just a goosed electrical component inside the servo but it's odd that it cycles like it should. Hope someone can help!