Difficult to say, regarding the age by the VIN. The problem is a lot of swaps have taken place over the 28 years the NSRs have been around!
Here's a basic run down for you:
All NSR250 crankcase castings are designated MC16E. (Not all NSR250 cases, notably many HRC ones, are stamped though.)
1987 MC16:
Solid engine mounts | crank with separate centre seal | hex barrels/heads with 90° alloy outlets & additional small brass hose unions | small exhaust port windows & RC Valve flaps
1988 MC18 R2J/R4J SP:
Rubber engine mounts | crank with separate centre seal | hex barrels/heads [top head with steel spigot] | large exhaust port windows & RC Valve flaps.
1989 MC18 R5K/R6K SP:
Rubber engine mounts | crank with integral centre seal | hex barrels/heads [top head with steel spigot] | large exhaust port windows & RC Valve flaps.
90~93 MC21 R/SE/SP:
Rubber engine mounts | crank with integral centre seal | round barrels/heads [top head with steel spigot] | angled exhaust port windows & RC Valve flaps [for reduced piston ring wear].
In 1991 the crankcases and oil pump were redesigned, for additional crankshaft lubrication on some models. In 1992, the modification was carried over to all engine variants.
94~97 MC21 R/SE/SP:
Same as late MC21.
_________________
Andy.
NSR-WORLD.COM
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