I put a Big Bore kit on my Makita dcs6401 and it ran great for a number of years. Two months ago, I was cutting up a large oak that was in my brothers neighbors yard. I was in a cut and felt the power drop down until it stalled. I tried to pull the cord put it wouldn't budge. i knew that was a major issue. After it cooled I pulled the cord and pulled like no compression (there wasn't) I smoked it. I pulled it apart and found cylinder wall scored and the piston ring/piston damage also. The bottom end was still good. I ordered another Big Bore kit and installed it. Emptied the fuel, cleaned the filter, replace the hoses, pulled carb apart, sprayed the carb passages and blew out with compressed air and reassembled. When I got some fresh gas,fired it up and it sounded good. I left my saw in the cold shed. The next time I TRIED to start it, when I pulled the cord, I could tell it was hydro-locked with fuel. Not just enough to foul the plug, but I poured a good amount of raw fuel out of the sparkplug hole/combustion chamber. This happened to me with another saw, but to a much lesser extent. When I filled THAT saw, I topped it off and then left the saw in my van that would get toasty in the summer sun, fuel expanded with the heat and forced enough into the cylinder that it fouled the sparkplug. I just don't "top off" the fuel anymore unless I would use the saw immediately. The question is, what part of the carburetor would cause this? Maybe the compressed air was too much for it. I will at least buy a rebuild kit, but maybe a new carb, if available would be better. Any thoughts?
