1973 Kawasaki 750 Mach IV H2A
1975 Yamaha XS500B in XYZ
model summary
Changes for 1973 were limited to a tasteful toning down of the styling and relatively minor changes to the powerplant and chassis to deal with issues found in the first year's bikes.  Essentially the bike was the same as the previous model, just with a few of the worst rough edges removed.
bodywork
1 New tank and ducktail striping in line with rest of the range
2 Front mudguard chromed
3 Seat and fuel cap now lockable
4 Colours: Candytone Gold, Candyone Purple
engine
1 Transfer ports lowered
2 New gasket and sealent for CDI cover to prevent water ingress
3 Carburetion leaned out to reduce emissions
4 Shims added to gearbox to avoid popping out of gear
running gear
1 Tread patterns changed on both tyres
2 Fork damper cylinders changed to avoid clunking
3 New fork seals fitted