ok having read some archived posts on this site regarding "why my rear cylinder popped" it went in depth about cylinder heads.
Could someone enlighten me as to whether the heads on my engine are correct:-
one is embossed kv3e-1 and the other embossed kv3e-2 both have the side mounted spark plug and a water pipe with a bypass pipe the lower cylinder having this blanked off.

once i have established whether or not this is the problem i can look deeper into why it went bang.

thanks liam