Duuh, I forgot about the wristpin retainer. There are little pieces of wire circular shaped that go at each the end of the pin that connects the piston to the crankshaft. Here is a picture of one, not for the CEN, but you get the idea:
http://www3.towerhobbies.com/cgi-bin...?&I=LXLBV9&P=7


Sad to say that I have two GST's. Got the chassis and they were pretty good and rebuilt them last summer and put new engines in them and just finished the heat cycles on one of them and ran out of weather. I still have aluminum foil on the head. Thanks for the heads up on the wrist pin problem, I hope to be past that stage with mine.