CB400F failure

[Mikep328]

 If cylinder cooling/oil breakdown was a problem, wouldn't there be a lot of historical data indicating these engines suffered from poor cooling/oil issues?  Everything I've read indicates the opposite - that they were essentially bulletproof...other than the oddly designed cam chain tensioner!   

[Bryanj]

OK the cb/cd 175 of the era had a habit of shattering rings if pushed hard from cold with the bits exiting the top of the piston in exactly the same way if not noticed soon enough, the 250K3/4 would also ocassionaly do this as well, not seen it on a four except for this one and nurse julies build.
Only throwing ideas out there

[Mikep328]

Wouldn't it be more likely that the damage shown in this thread was more related to improper fueling (too lean) or improper ignition timing - either too advanced (detonation) or retarded (overheating)?