Chainsaw Repair

Have you checked your fuel line and filter? When you say 'bogs out' is the saw starved for fuel or flooding? If it is starving for fuel, perhaps the filter is not the correct one or it has become disconnected from the line, causing the line not to seek the lowest point in the tank when in the bar-down position. If ir is flooding the most likely it is the carb or impulse.

Have a look here:

http://chainsawrepair.createaforum.com/ported-saws/where-to-begin-when-you-saw-does-not-run-right/msg41282/#new