Fitted new carbs – brand new remanufactured Amals. I didn’t really know how to synchronise them, so made do with a technique I made up on the spot. I hooked them up to their throttle cables, laid them flat on timbers laid down alongside the frame top-tube so they couldn’t roll off, and measured slide aperture against the throttle stop screws to equalize this aperture. Then I eyeballed both slaides as the throttle was opened and adjusted the cable of one until its slide could be seen to move at the same instant as the other. I then fitted the carbs on with the stock airbox assembly again.
I struck a problem with carb studs unscrewing out of the cylinder head as the old carbs were removed. Had to re-insert with Loctite and use pliers to get them at least a little bit tight, as there are no flats on them and not enough thread to get two nuts on for the time-honoured double-locknut method of tightening studs. I hope they will hold and not cause flange air leaks – need to check this often.
Mileage at which new carbs fitted – 19,387.
Bike now runs good when accelerating hard – very clean pickup and absolutely no missing or flat spots. It idles like shit, although I had the mixture screws 2 ½ turns out (as per the manual) and this must be way too lean. The pipes blued, plug was brown-white and engine backfires on the over-run. Setting it at 2 turns out brings a big improvement. But idle speed is not steady – air leaks?
Took carbs off again to investigate, and re-loctited studs of RH carb. Used washers to pack out the nut on the stud so it wouldn’t bind up on the thread, and used it to get the stud seated in the head. Despite there being a collar on the stud, clearance is such that the carb flange nuts will compress the carb’s intake stubs against the head. I am not quite sure what this collar is for. Pre-unit Triumphs seem to manage okay without it.
Pilot mixture screw now set at 1 ½ turns out. Engine feels “happy” and picks up fairly cleanly throughout the rev range. Once warmed up it idles evenly, and idles at the same speed both before and after going out for a good hard thrash. Idling at traffic lights is now a “hands-off” affair.
But occasionally, e.g. on re-start, it won’t idle, backfires through the pipes, and will miss and hesitate when accelerating hard in the higher gears at ¼ - ½ throttle. Then after a few minutes it will come right again. Is there shit in the floatbowl, holding the float needle open?
The bike is still running the standard air boxes, which don’t seal or filter at all. Better to wait until the K&N-type filters arrive in the mail before more time is wasted trying to get the carburetion spot-on. For now, the bike runs pretty good. Pulls strongly and evenly up to 80mph. Throttle does feel rather heavy, and “notchy at small openings.
