The NSR250 has 3 barrel sizes with 3 matching piston sizes:
A barrel <--> B piston
B barrel <--> Blank piston (no mark)
C barrel <--> D piston

@ Tuckerbug - Both my pistons are blank, yet both of them fit into either barrel (B or C). My pistons are basically new, if they have done 100km/60miles it would be a lot.

Also, this may be of some interest to you,..
I have blogged my restoration of an NSR250SP MC18 R6k.

@ Tuckerbug - I have actually read your whole blog, kind of the inspiration behind me pulling my one out of storage. Looking at it now, I wish I left it where it was...




Some new revelations on my two different barrels. Had an even closer inspection, and look at what I found on my supposedly MC18 'B' barrel... A damn hole... the previous idiot who 'raced' it obviously never adjusted the RC-valve correctly, and this is the result. See photo below.

My new question... How will my bike run if I get another MC16 barrel like the one on the left (photo above), and bolt that on. Also keeping in mind that my bottom end is straight out of a MC21. I will be using my standard R5K/R6K carbs, R5K/R6K exhausts and PGM2 CDi. I can get my hands on both MC16 and MC18 barrels, what the condition is, I dont know.

Jacques.