I've been chasing a ghost for a while trying to solve a low speed skip problem on a '61 +4DHC (triumph engine)
I thought at first that it was an ignition problem, but I replaced the ignition system (I have spares) and re-timed and had no success. Compression checked out (150-155 on all 4), so I started looking for vacuum leaks. The only vacuum leak I can find is on the throttle shaft bushings on the carburetors. I pulled the shafts out, and measuring with calipers there's about .006" clearance between the shaft and the bushing. I don't know SU's very well, but this seems like too much clearance. It looks like the shaft is supposed to be .3100" diameter, but I don't know what the spec is supposed to be for the bushing bore.
What's considered acceptable before parts need to be replaced? Anyone re-bush one of these carbs?
