I think there more differences in the cylinder than just the decomp. valve. I think what trimmed is calling the 55 "classic" was the original 55. It had a closed port cylinder (I think) and was 51 ccs (no, i'm not confusing it with the husky 51, which was 49 cc's). It was rated at 3.4 hp and came with .325 chain and a rim sprocket. The 55"rancher" is an open port version ,with 53 cc's and no decompressor. Rated at 3.3 hp, it came with 3/8 chain and a spur sprocket. I believe the original 55's came with a walbro carb. and the rancher has a zama.