Took the bike out for a good hard run to Nausori over the Sawani Hill road. If anyone wants to know where that is, then use Google Earth. Bike still runs rough and misses every so often, then smooths out again. On the way back the throttle started sticking open at ¼ - ½ throttle openings and needed to be taken wide open and released suddenly to free it each time this happened.
Over-tight carb flange nuts were immediately suspected. Back at base, both carb slides were removed and inspected. RH carb shows shiny high spots (just above cutaway in two places, and vertical stripes of wear). LH carb had one very slight high spot. Tried moving slides in carb bores by hand – RH one definitely goes tight at ¼ - ½ openings. LH one was okay. When operating by twistgrip, its action definitely goes through a “tight” spot.
Slackened all carb flange nuts about ¼ - ½ turn. RH slide immediately freed up, and throttle action feels light once more. Reassembled, and tried to ride it but now it feels very gutless and misses a lot – most unrideable. By now it was dark and I had to pack it in for the night. Presumably I now have to start from scratch and re-do the set-up of pilot mixture and throttle stop, as per the book.
Believe it when the books say “Do not over-tighten the carb flange nuts on Amal Concentrics”. It is fortunate that slackening these nuts resulted in the slides freeing up again. Could have cost me NZ$200 to get yet another carb!
It is a delicate balancing act between having the carb flange nuts tight enough to seal but not so tight that the carb bodies distort. This is certainly not an idiot-proof procedure like on Japanese bikes. Even the Monobloc carbs of pre-unit Triumphs are far superior, because their screw-on tops act as a reinforcing ring around the carb body.
