Replacement of Poulan chainsaw carburetor
Model: SM4218AV PRO 42cc
The chainsaw is about 10 years old and is infrequently used. As a result, every time I go to use it, I have to work on it – mostly the fuel system. Usually all the gas hoses to the carb have deteriorated and have to be replaced. I’ve also had problems with the carb gumming up. I’ve taken the carb apart and cleaned it but it just seems not to work just right.
Ebay and elsewhere has replacement carbs. But even though they do say they fit, I’ve found – after buying a couple of them over the years – they don’t quite fit right. These replacement carbs have a metal extension piece on top of the carb opening the upper butterfly that is different than the original. See photos.
Note that it extends over the rubber bulkhead isolating the carb compartment from the cylinder head.
I ended up simply trimming the cover where it fits against the rubber bulkhead.
Also, after not properly documenting the routing of the gas lines, I had an issue with reassembly. This diagram was very helpful. I conclude that the larger inlet gas line comes in on the right side (the side with the throttle linkage, inlet is lower down on the carb) and the return line is on the left side (with the choke, stop levers and adjustment screws, outlet is higher up on the carb).