Preparing to port first saw - which one, and what method?

[mainer_in_ak]

Put a big bar on it and see how it does.

No need, I run 20-24" on all my 60-67 cc fodder.

Nother 67 cc saw:
MS 400 without a base gasket and no port work:
100.5 degree exuahst roof. 122 and 126 on the transfers. With the lighter magnesium piston, it cuts about 1 second faster.

 

[jacktheripper]

OK, so I got to test it. With the transfers done it gained torque and speed. It is now 4-stroking at 14k, and pulling 11.5k in the cut. Throttle response is way snappier, and it sounds meaner too. Compression is at 170 plus here at 5500 feet, which converts to over 200psi at sea level. Totally psyko-ss-insan-o, baby!

 

[jacktheripper]

I’m a “bit” of a stranger to the model. What’s the current slug look like?

Like Mike CFB said, the numbers are only part of the puzzle. You have to physically look at what’s going on as well. How much of the lowers does the piston cover after the intake floor closes? Where will the crank weights be at that time? What’s the case/displacement ratio?

There’s a pretty good chance that the windowed slug is going to increase case volume and decrease crank compression pressure. This will make the saw a slug to recover when it’s dawged down in the cut.

A lot of the older husky’s have assymetric uppers from the factory. Were yours even?

Your port work looks nice. Exhaust roof symmetry is sometimes easier to check with a piston in the bore. The only thing I don’t love is how big your uppers look.

Thanks for commenting! I know that gains have been made from using the windowed piston instead of the full circle one. I guess this will result in a bit of trial and error. I did slope the lowers, which would add additional case volume. I just don't know if the windowed piston will put it over it's threshold. As for the uppers, I raised them to the same level. I know that the flywheel side was about a degree or so higher. My thought was that I would want more oil getting to the clutch side bearing, so I would even them out. I don't actually know if that's good reasoning.

 

[MG porting]

I guess when you're cut wood that's only 20" across then yeah building something that seems 15,000rpm is fine.

 

[jacktheripper]

I guess when you're cut would that's only 20" across then yeah building something that seems 15,000rpm is fine.

What do you mean?

 

[mainer_in_ak]

I guess when you're cut wood that's only 20" across then yeah building something that seems 15,000rpm is fine.

Neighbor runs a 28" bar doing 18-20ft rip cuts. He's well over 10 gallons of mix on his 67 cc saw. 104 degree exuahst roof, 122 on the transfers, 180 psi.

He borrowed my 67 cc saw and used his 28" mill. He noticed faster cuts with my saw. Anyhow thanks for the lessons on torque.