When I took the ride-out at the Shepherds Rest, we had one breakdown. The cam belt on Marks MT500 snapped. Well, due to the design, this causes no valve damage, and he had the cover off, and his spare belt fitted in half an hour at the roadside. Impressive 
Half an hour!!! 10 minutes tops.

Harley MT350 electric start/left kicker, discs front and rear, CV carb, panniers on front.(American)
Armstrong MT500 left kicker only, drum brakes, Amal carb, panniers on rear.(British)
There is also a Harley MT500 in USA same as our 350.
All bikes are capable but at different speeds, there is a fair difference in usable power on the 500 for loaded up touring.