As I've probably mentioned I had no end of problems with the little 400 4 I had briefly. Eventually tracked down to a defective plug cap although the vacuum fuel tap was also problematic. Probably no help to you......
Thanks Ian.
I think I've had problems with most aspects of this project including the fuel tap (leaking but repaired with a kit from NRP Diaphrams which required rivets drilling out and tiny new threads being cut,beyond my limited skill set) buying the wrong type of NGK plug caps for the tiny aperture they live in and then struggling to remove them to put in the correct type.
Some of the other problems have been mentioned earlier in this thread.
I found lots of debris inside the fuel filler area which have blocked the tank breather. It's been vacuumed out now hopefully.
A brief test ride went well this morning and I intend to venture further afield in the coming days.
These problems cannot be laid at the door of Mr. Honda as my bike has been through the hands of numerous owners most if not all of whom probably did little if any maintenance. My bike is now 37 years old so after all the work which has been done in my ownership hopefully it will continue to survive in to the future.
