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.
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?
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.
Blow down is very important.
20 degrees is the safe number a lot of new porters use as you know it will work.
15 degrees of blow down on saws with the exhaust at 105ish works on a lot of saws. I've found you want the transfers to open at about 120 degrees atdc on most saws and if you have a smaller saw with the exhaust at 105 you have 15 degrees of blow down, if you have a big saw with the exhaust at 100 you have 20 degrees of blow down.
Opening the transfers sooner/less blow down lets the exhaust help pull the mix up out of the bottom end but if you open them too soon (like the transfers opening at 110 atdc) the exhaust will push the mix back down the transfers. Short blow down saws are very snappy because of this.
The bottom end has to compress the mixture so it will flow up through the transfers, if you make the bottom end bigger volume wise by making the lower part of the transfers wider it doesnt compress the mixture as much so it doesnt shoot it up through the transfers as fast. You need to find a happy medium between adding flow and not adding much volume.
I built a few 54cc zenoah clones(they're a very similar design as the poulan 2150), these saws have the exhaust too high and you cant fix it, 104 is better but 100 is as low as I can get it.
One has the exhaust at 98 and the transfers at 122, the other the exhaust at 100 and the transfers at 118, everything else is about the same. The saw with the transfers opening at 118 is snappier and stronger bucking large wood, the one at 98 and 122 is better for small wood as it revs higher.