Terry Syd
Addicted to ArboristSite
I purchased a Works Connection tach to mount on the saw so that I could fine tune the carburetor. I've taken a few more passive coils off the metering spring to improve the spread of power and I wanted to see if I needed to take any more off. It looks like I've got about the right POP.
When I lowered the POP I found that the saw was becoming too rich off of idle. Since I had previously leaned the throttle plate by filing a small notch on the side opposite of the idle circuit, I went ahead and soldered the notch back up. I then could lean out the Low speed screw and keep the fast throttle response. What was happening with the lower POP was that the metering needle was able to lift off the seat at the lower air speeds and enrichen the mixture. - That is a good observation for saws that may be a bit lean off of idle. A drop in the POP will allow more fuel off of idle and allow more low end torque.
With the tach, the High speed needle was very close, I only leaned it a tad to get the best cutting speed.
I could never get the 20" chains to stretch enough to mount with the 8 pin. So I just bit the bullet and purchased a 365BB with a 24" bar to do the big stuff. The 8 pin and 18" bar with the 5 degrees of cutting angle works very well. The saw feels like it wants a bit more cutting angle, but the 5 degrees works so smoothly on limbing small limbs that I will leave it at 5 degrees.
The saw does its best work between 10-11,000 rpm. That is consistent with the .0066 m/sec transfer time/area at 10,500 rpm that I learned from Blair's work. I thought that the .0066 may relate to peak torque, but it appears to be peak horsepower (at least with the mods I've made on this engine). Peak torque appears to be around 8,500-9,000 with the saw still pulling fairly well down to 7,000. I've pulled it down to around 6,000 and it doesn't want to bog, it just cuts too slow to be of any use. Even with the 8 pin, I don't find any problems with bogging, the powerband is just so broad that you have plenty of warning.
The 13,000 limiter is not a problem. With the best cutting speed in the 10-11,000 area I find I am loading the saw on smaller wood to keep it in that range. With the bar buried in hardwood, the saw tends to sit around 10,000 rpm with just a light pressure on the bar.
When I lowered the POP I found that the saw was becoming too rich off of idle. Since I had previously leaned the throttle plate by filing a small notch on the side opposite of the idle circuit, I went ahead and soldered the notch back up. I then could lean out the Low speed screw and keep the fast throttle response. What was happening with the lower POP was that the metering needle was able to lift off the seat at the lower air speeds and enrichen the mixture. - That is a good observation for saws that may be a bit lean off of idle. A drop in the POP will allow more fuel off of idle and allow more low end torque.
With the tach, the High speed needle was very close, I only leaned it a tad to get the best cutting speed.
I could never get the 20" chains to stretch enough to mount with the 8 pin. So I just bit the bullet and purchased a 365BB with a 24" bar to do the big stuff. The 8 pin and 18" bar with the 5 degrees of cutting angle works very well. The saw feels like it wants a bit more cutting angle, but the 5 degrees works so smoothly on limbing small limbs that I will leave it at 5 degrees.
The saw does its best work between 10-11,000 rpm. That is consistent with the .0066 m/sec transfer time/area at 10,500 rpm that I learned from Blair's work. I thought that the .0066 may relate to peak torque, but it appears to be peak horsepower (at least with the mods I've made on this engine). Peak torque appears to be around 8,500-9,000 with the saw still pulling fairly well down to 7,000. I've pulled it down to around 6,000 and it doesn't want to bog, it just cuts too slow to be of any use. Even with the 8 pin, I don't find any problems with bogging, the powerband is just so broad that you have plenty of warning.
The 13,000 limiter is not a problem. With the best cutting speed in the 10-11,000 area I find I am loading the saw on smaller wood to keep it in that range. With the bar buried in hardwood, the saw tends to sit around 10,000 rpm with just a light pressure on the bar.
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