I'm restoring my first airhead, a 1973.5 (LWB) R75/5 and having issues with throttle response/power. I've adjusted the valves, checked the points, replaced plugs, set timing, carbs cleaned and rebuilt with new o-rings/diaphragms, and carbs synced. The bike starts and idles with no problems and runs solidly. It feels underpowered though, slow throttle response and speed tops out around 70mph. At idle, I see the timing mark moving around a bit, and a double mark sometimes. To keep idle down to 1100-1200, I'm at a half-turn out on the idle mix, vs the 3/4 recommended by Bing.
Any suggestions for what next? I haven't checked advance timing, will do that tonight.