I'm sure you have already thought of it, but make sure you give the oil system a very good flush out - there is probably a lot of combustion product in the oil... Seems like it was not as bad as it could have been. As has been said though, why did it crack? Maybe more investigation - would not be good if it did it again...
So what caused it, how many miles has the engine done....what cpu are you running it on has it ever had the fuelling checked on a dyno.......
I have no idea what caused it, same as I have no idea why the sprag went.... Apparently the pistons are shit and it's a common failure....Fucked if I know mate. 16M ecu. No, not had the fuelling checked on a Dyno. 12k miles (ish)
well im f#ck*d if I know what your on about buddy too lol. at first your saying you cant rebore a nicosil plated barrel - what bollox. of course you can. get it rebored and replated, in the case of the 999 you can get upto +2mm for 1038cc from stock cylinders. and then your saying if its damaged it needs replacing or replating - yet another contradiction roflmao.. see above. make your mind up lmao.. and you can light hone nicosil to deglaze. ask any specialist
There are also far superior platings that can be done over standard, many who race tune engines replate the barrel for longer life etc from brand new!
Ive replated nicasil on tuned TS1 lambretta barrels. Stan Stevens did it. Or he sent it to someone who could anyway. Was fine, even if i did rebore it afterwards again and drop a steel liner in.