I just got a 020T off Ebay. The seller said it had 120# compression but wouldn't start. I checked the compression after I opened the box and after numerous pulls it ran up to about 120. I released the pressure and did it again and it didn't make 100#'s after that the best I can get is 50#'s with several trys. I never started the saw or did anything else. Am I missing something? I don't belive these have a decompression valve. Also there is no model number on the saw. Where do I find the sertial number to verify the model? Thanks