Stihl 026 porting numbers.

[bretts]

I run the timing wheel over my 026 today...
I am trying to get my head around timing numbers on saws
I am using a Hyway 44.7mm cylinder that is stock but will be looking to port it.
Squish is .17 with no base gaskt
Ex opens @104 atdc, closes @87 abdc
T/fers open @134 atdc, closes @59
Intake opens @75, closes @78atdc
Are these numbers ok, are they what you expect to see?
Any help appreciated.

 

[farminkarman]

I run the timing wheel over my 026 today...
I am trying to get my head around timing numbers on saws
I am using a Hyway 44.7mm cylinder that is stock but will be looking to port it.
Squish is .17 with no base gaskt
Ex opens @104 atdc, closes @87 abdc
T/fers open @134 atdc, closes @59
Intake opens @75, closes @78atdc
Are these numbers ok, are they what you expect to see?
Any help appreciated.

A couple things….to keep it less confusing, reference your port opening times from TDC. Another thing, your port opening times need to come out the same. For example, let’s say you measure intake closing at 74 and you keep turning the crank and it opens at 78. That means your timing wheel isn’t zeroed. If it were zeroed, your reading would be 76 & 76. As for the squish, I would run it no gasket at 0.017”. Make sure your wheel is zeroed and report back.

 

[farminkarman]

One more thing….i wouldn’t plan on porting a Hyway cylinder. The plating doesn’t like to stay put on those when you start grinding.

 

[Stump Shot]

@farminkarman is correct on his assessment of the situation. All is not lost however. The squish is set, forget about the "numbers" as you do not want to adjust them anyways because of the poor plating adhesion. Do what you can, without getting into the cylinder part of the exhaust port shape and enlarge as you would like, match your intake and exhaust ports to manifolds and muffler as well as mod the muffler and an ever so slight adjustment of the ignition timing and you should have yourself a decent running saw.
The plating is worked over the edges of the ports and this is what keeps it all in place, therefor if the port edges are not touched it will stay together for you.
Best of luck with your project.