This next iteration all I did was rough up the intake a little bit. I saw a video on YouTube of a guy that did one of these saws and he roughed his intake. Not sure if I roughed it enough, it didn't seem to do much.
I'll be moving on to widening the ports, lowering the intake, and raising the transfers. Any opinions and what I should do first? I would like to do it steps so that I can see what each mod does to the saw like I have been doing.
I watch the tinmans vids too, he's a nice guy but cant build a fast saw. He runs high exhaust and long blow down in everything, it's good for limbing as they rev high but they cut like stock dogged into big wood.
Getting the blowdown as short as possible without going too short is the key to having a strong saw. Keep the intake under 80 degrees or they get lazy and on a 50cc saw try to stay around 105 on the exhaust.
If I was porting that saw, I'd lower the intake to 78-79 degrees, raise the transfers to 118-120 and make the intake/exhaust wider. I dont know what the lower transfer look like, I only grind them a little on most saws, adding volume is bad if it's not adding a bunch of air flow, having big hogged out lower transfers will make the saw lazy.
Tinman's videos are definitely a good place to start for any beginner, he does say that it his method and there are lots of way to achieve the same result. No complaints with his videos.
This saw is only 36cc, not sure if that changes any of the numbers you posted. The saw has open transfers.
Why is blowdown important? Does the fresh charge from the intake coming in sooner help push out the exhaust and therefore make a more efficient saw?
Not sure if my thinking on that is correct.
"adding volume is bad if it's not adding a bunch of air flow, having big hogged out lower transfers will make the saw lazy."
Could you explain this?
so by raising the transfer your going to start pushing exhaust out earlier and getting fresh air in sooner which ends up being more burnable mix in the cylinder. You can go to early and start back stuffing the transfer but in your case 15 degrees blow down is where you want to be.
The removable dome might not be something you want to try on you first go around but it is a way to up compression without a lathe or mill. It was used in motocross engines and basically its a chamber that goes inside your current one and shrinks the size down.
you will have to cast one your self but it's not terribly hard and doesn't require to much for special tools but you will need a tap and die set for sure. if it's something your considering PM and I'll help you.
Why is blowdown important? I'll pose the same question to you as I asked NSEric above.
I probably won't do the removable dome on this build but I'll eventually PM you about it.