Intake durations

[Fordhook]

Hi guys new to the site.
I've been tinkering for sometime with 2 strokes and recently turned my attention to saws. I use a 365 and 353 for work and firewood etc.
Anyhow I just put a Meteor 372 top end on my 365 and ported it. Pretty happy with the results.
My 353 I got 2nd hand and the jug was junk so just fitted a Meteor 45mm top end to that. I cut the jug for .5mm squish and ported it but it wasent were I had hoped it to be. I was hoping to keep the muffler stock but after adding a second port it got going and more like what I was expecting. But there are some sweet running 346 on YT that would kick mine to touch. I suspect they are running a pop up but if a deck my jug now my intake will end up some where around 84 deg.
This seems too much to me but Id be keen to hear what a few others think or even better to hear from anyone running a number like that.

 

[weimedog]

I try to keep my 372 saws in the 78-80 btdc range for the work builds. Conservative. From what I have seen it's not that you will loose the ability to run, but they get lazy off idle when you get past the low 80's btdc. The most I ever intentionally built into a saw that's still running is 82 BTDC and that was on an old Jonsered 820. Huge case volume. Of course that is with the saws I tested, every saw design is different. Carb size and intake tract dia. effect things as well as down stream conditions like case volume and transfers port size and timing. Other builders will have other numbers that match their total build recipe's as those numbers all work as part of the system that is the saw motor from muffler to air filter.

 

[Fordhook]

I try to keep my 372 saws in the 78-80 btdc range for the work builds. Conservative. From what I have seen it's not that you will loose the ability to run, but they get lazy off idle when you get past the low 80's btdc. The most I ever intentionally built into a saw that's still running is 82 BTDC and that was on an old Jonsered 820. Huge case volume. Of course that is with the saws I tested, every saw design is different. Carb size and intake tract dia. effect things as well as down stream conditions like case volume and transfers port size and timing. Other builders will have other numbers that match their total build recipe's as those numbers all work as part of the system that is the saw motor from muffler to air filter.

Thanks for that.

I ended up using JB and set it 78 BTDC
For a little saw its running surprisingly well. The compression ratio is a little low so I ordered a new piton with the intention of cutting the squish. But I spent a day with it at work and liked it as is with 20 inch bar and 3/8 full chisel. I'll just leave it for now and run the pop up piston for a bit, if a need more torque on some bigger wood I'll look at it then.