How DOES stuff get in there?!

[andrethegiant70]

I rebuilt this carb maybe 8 months ago. It is from a Jonsereds 910 that I use for milling. The saw began to hesitate when I blipped the throttle, not badly at first but it got progressively worse. After finding no other reason the saw might be running badly, I broke open the carburetor to find quite a lot of sawdust. I'm confused I suppose, but if I'm running a good fuel filter, how does sawdust get into the fuel system? Check out the pics! Opinions welcome!

 

[PES+]

Both places where you have saw dust are open to the air cover area and are not filtered. You can help minimize this by sealing up the top of the air filter cover where it mates to the cylinder top cover. It is one of the reasons I do not use too shallow an angle on ripping chain (but that is not my main reason for non popular angles for ripping chain).You can also tray making an open cell foam cover to lay over the carb under the air filter to keep the fine dust out of the atmosphere parts of the carb.

You will not need to rebuild the carb again just clean out all the saw dust and keep the carb body from seeing so much fine dust.