After a few world with Carl, he suggest that is very difficult to bore r 100 cylinder, so after my last attemp of install oversized rings failed, my last chance before buy new cylinders (i cannot find them is a 78 r 100 europeans specs engine, i think with big valves) is to send them to a bore service and new pistons in Rennsport facilities. What would you do? The moto bins alternative (all new) is very expensive over 1000 usd plus shipping. I cannot find new cylinder on max bmw pages, were to find them??