With regards to the cranks I bought a stripped U/S crank and have some old NSR cranks of various years to compare. The NF5 cranks are very similar to the MC18 mk1 cranks with the separate centre seal (later NSR cranks have the centre main seal integral to the centre main bearing) The centre seal is exactly the same dimension as the mc18, pattern ones of these are readily available from Japan. The main bearings are identical except for the right hand bearing which Les pointed out has a nylon damper ring around the outer race but dimensionally is the same, the big ends are the same pre 91. The 91 and 92 have the conrod support type crank with no thrust washers in the big end and a wider con rod and big end bearing.

The Koyo NSR main bearings are available from various sources, the Big end I believe is the same dimension as the CR250 big end and the centre seal is available as a pattern part. The left hand main seal is still available form Honda, the right side main seal is an MC18 part and is available as a pattern part from Japan or can be replaced with a later NSR part.

Like the NSR cranks they are rebuildable dependant on the condition of the big end pins and conrods. I was planning to have one rebuilt at some point but I need to finish my current projects first