dbabcock
Hi Tech Redneck
I've become interested in 2 stroke port timing lately and I'm curious what some of the saw builders here use for their figures. It seems that there are some pretty standard "cookbook" numbers that most people start out with based on application and what other things have been done to the motor, like higher compression, pipes, reeds, etc.
While I had the flywheel off the 3120, I put a degree wheel on it and measured about 170 degrees of exhaust port timing, but I have no idea about the intake and transfer port figures. I think Ken once told me that the 170 degree number can go upwards of 185 degrees if a head is machined for the saw to up the compression. I think the more exhaust duration that is put in, the lower the effective compression ratio, so this is why stock barrels rarely have more than 170.
I put the wheeel on my 266 and measured something like 145 degrees, but I can't remember the exact number. My 2149 was a real eye opener: 224 degrees! Man, that's more than high-end motorsicle two strokes run. No wonder the little thing motors!
These are the secrets of the masters, I guess!
While I had the flywheel off the 3120, I put a degree wheel on it and measured about 170 degrees of exhaust port timing, but I have no idea about the intake and transfer port figures. I think Ken once told me that the 170 degree number can go upwards of 185 degrees if a head is machined for the saw to up the compression. I think the more exhaust duration that is put in, the lower the effective compression ratio, so this is why stock barrels rarely have more than 170.
I put the wheeel on my 266 and measured something like 145 degrees, but I can't remember the exact number. My 2149 was a real eye opener: 224 degrees! Man, that's more than high-end motorsicle two strokes run. No wonder the little thing motors!
These are the secrets of the masters, I guess!