Chainsaw Repair

@Roanoker494  said

I have worked with many 50-55 series Husqvarna saws and have become very familiar with the parts interchangeability. In my experience 99% of all parts are compatible between the models 51 and 55, not 100% because some of the 51's did not have the air injection. The model 50 made several changes over the years and not all parts are compatible from all years. Before 1987 the model 50 had a smaller opening in the crankcase for the piston/cylinder so modifications are required to install a 51/55 top end onto the pre 87 model, though no mods are required to install the pre 87 top end onto a 51/55. The 50 also has the different choke system which, in my opinion, is inferior to the 51/55 setup. There was also some changes between the 50 Ranchers, commonly found with a white top cover, and the later 50's, commonly found with a grey or black top cover. The major differences were cosmetic with the recoil cover and chain brake assembly, you can not use the brake handle/flag from a 50 Rancher on the later style brake cover but you could swap the entire assembly without issue. I have often heard about there being different bolt patterns on the cylinders but I have yet to ever see it myself with having worked on saws made from 1983 through early 2000.

Parts numbers for the closed port
Complete top end 503971871
Piston alone 503168771