Craftsman II snow blower tracks lock up

Hello, Just took a look at a 208cc briggs the other day on a snowblower. Neighbour has one and asked my opinion on it. This machine can backfire like no tomorrow. It will back fire on start or will backfire if you give it too much throttle too quickly. The carb on it looks like there are no adjustments. Im thinking it is running too lean. If I cannot adjust the carb, is there anythnig else I can do to prevent this gun shot from occurring. I mean like this is a heavy duty crisp backfire. Scares the entire neighbourhood. Looking around some forums it looks like there are many other out there experiencing the same thing. I thought i would come to the professionals at DIY to see if anyone has exepreinced the same thing and could provide some advice. Thank you,

I have a Poulan 3300 chainsaw that has performed without flaw over the past several years. Recently I got it bound in a tree and ultimately the sprocket/clutch area began smoking. I freed the bar and started the saw again. The engine runs great and the chain turns a bit with no load. Under load the motor runs perfect but the chain doesn't move. Looking online I noted several parts are no longer available. Please advise what action I need to take/what parts I need to purchase. Also, how do you remove the clutch? Thanks in advance