I had a 600 that was a sleeved down 750.
Put 750 barrels on and it becomes a 900, not to mention dif cams, chain, ig, top crankcase and the clutch and gearbox mainshaft were different.
On a 100% sound bike low miles that had its oil changed every 3000mls running like a swiss watch, yeah maybe bore it.
On a 125 for maybe 5hp.