So, as far as you can tell the machine can't go over about 2.5 gram shot? That is unfortunate as I was really hoping to get a bigger shot out of the unit - looking for about 6 to 8 grams in fact. I have to wonder if there is any room for a redesign of the clamping or the injection pressure by either increasing the size of the air cylinder or making a latching clamp action on the mold so the injection pressure can be increased. As you say, if the injection pressure rises the liquid plastic may weep out at the mold lines otherwise.
I have a photocopy of a photocopy of the original manual for the CPU controlled version of the 2/3 (email me if you want a PDF copy - or can I put it up on this site somewhere?) and while it talks about how to remove the injection chamber I can't get the pin out from the underside of the securing part that is accessed by removing a 10mm bolt from the side of the frame just below the hopper. The instructions say to drive out the pin using a 4mm rod inserted into the hole, but I whacked that a couple of times and the pin did not move and I don't really like the idea of hitting it harder until I am sure that is the correct spot to be pounding.I will put up some photos later today of the parts I am speaking of.