Wild Knight
ArboristSite Guru
The ring pin is located in the exact same position on my 441. I thought the same; it is located exactly to prevent widening of the exhaust port.
Obviously, you have noticed the strato cavities on the piston. These hold extra air that is added to the transfer charge, thereby 1) scavenging the exhaust and 2) leaning out the fuel charge. I think you are on to it now, but the mixture coming in through the intake is rich. It has to be b/c fresh air is being added by the strato port. If you enlarge the intake, but leave the strato ports the same, then you will be getting more fuel into the crank while at the same time NOT leaning it from air from the stratos. You must open both the intake and strato ports proportionally. This is why you had to lean out the carb once you put everything back together.
FWIW, I ran Amsoil 100:1 for a while and will NOT be doing it anymore. When we got the saw apart, it had barely a sheen of oil inside. Additionally, the piston had gotten very hot. I think the only thing that kept it from seizing was the high amounts of anti-seizure compounds in Amsoil. 80:1 might be OK, but 100:1 just isn't enough oil. 50:1 will leave the insides blue like a little smurf village, which is what you want to see.
Obviously, you have noticed the strato cavities on the piston. These hold extra air that is added to the transfer charge, thereby 1) scavenging the exhaust and 2) leaning out the fuel charge. I think you are on to it now, but the mixture coming in through the intake is rich. It has to be b/c fresh air is being added by the strato port. If you enlarge the intake, but leave the strato ports the same, then you will be getting more fuel into the crank while at the same time NOT leaning it from air from the stratos. You must open both the intake and strato ports proportionally. This is why you had to lean out the carb once you put everything back together.
FWIW, I ran Amsoil 100:1 for a while and will NOT be doing it anymore. When we got the saw apart, it had barely a sheen of oil inside. Additionally, the piston had gotten very hot. I think the only thing that kept it from seizing was the high amounts of anti-seizure compounds in Amsoil. 80:1 might be OK, but 100:1 just isn't enough oil. 50:1 will leave the insides blue like a little smurf village, which is what you want to see.