Hello; Yes togatoga nailed it, the squishyness is the teflon pad that keeps the wrist pin from gougeing a groove in the liner. I once bought a used engine from a hapless fellow flyer, he had left the teflon pad out and now couldn't get any compression. I had to buy a new head/barrel and a lot of other parts to get it running (Saito 45 mk11), I put the "S" cam in it and donated it to our club trainer. It flew for 8 years with no further attention after that, excluding crash damage.