On rebuilders?? A little far out from you now but there is a guy in New Maryland (near Fredericton) named Sam Kay who does excellent work on these old bikes. He did the full tune up, valves, timing and carb synch on my 73 750 and it came back sounding like it just rolled of the assembly line. I am taking my wife's newly rebuilt 76 400F to him this spring for him to work his magic. Let me know if you need his info, I can PM it to you.