I had the same problem on both my .72's... I had the original back plates which broke all the time... I put the newer "redisigned" plates on that seems to have taken care of that... Also if you order a new gasket set you will find a mod in there for the intake manifold where it goes into the head... It simply consists of a small metal washer which keeps a little more pressure on the O ring.... I talked to Horizon and they were going to fix mine under warrenty but it cost more for postage then for the parts... I just ordered the parts (had to pay for them) and did it myself... No big deal... I have always loved Saito's but for what they cost these plastic parts just are not doing it for me ... I just bought a Magnum .70 to try.... Almost 100 dollars less and all metal parts with bushing on the con rods.... We will see...