Porting question

[vquinoveva]

Ok all you porters out there, when porting how much space do you need between the say exhaust and transfers to prevent interference or short circuiting? I’ve read in Jennings that he recommended .325 but this doesn’t seem realistic in a saw. Any suggestions or rule of thumb?


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[pioneerguy600]

The ports are timed by degrees.

 

[Huskybill]

The gurus on transfer, cylinder port timing will chime in. Lots of stuff on YouTube.

I lower the intake port, widen it a tad. Raise the exhaust port and widen it a tad. I trim the bottom of the piston skirt that changes the intake port timing. I match the transfers to the base gasket. And knife edge and lower the center rib. I don’t touch the transfer port timing.

I’ve done it this way for many decades. A two stroke is a two stroke.

 

[vquinoveva]

No I’m talking about the space between the side edge of the exhaust port window and the side of the transfers windows I’m not worried about port duration I’m talking from side to side and space between the port windows. I hope that makes sense


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[huskihl]

.325 is doable on most I believe. Depends on direction of flow also

 

[heimannm]

Hey Victor!

 

[vquinoveva]

Hey Victor!

Hey There he is, how are you Mark?


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[vquinoveva]

.325 is doable on most I believe. Depends on direction of flow also

In this case exhaust and transfers, what could a guy realistically squeeze out of that or is that in fact the limit?


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[wmazz]

You will be modifying angles that were designed to prevent short circuiting.

Bill M.

 

[vquinoveva]

You will be modifying angles that were designed to prevent short circuiting.

Bill M.

I understand this, however there is a razors edge to everything and I’m trying to find it


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[huskihl]

In this case exhaust and transfers, what could a guy realistically squeeze out of that or is that in fact the limit?


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I don’t remember actually measuring any saw other than an MS362. I couldn’t widen the exhaust port as much as I wanted. But those primary transfers shoot hard toward the intake. I’d stay further away on transfers that blew more toward the middle of the piston.
What model are you inquiring about?

 

[vquinoveva]

I don’t remember actually measuring any saw other than an MS362. I couldn’t widen the exhaust port as much as I wanted. But those primary transfers shoot hard toward the intake. I’d stay further away on transfers that blew more toward the middle of the piston.
What model are you inquiring about?

This is just a general question but after some experimentation probably an 066 and 3120


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[huskihl]

This is just a general question but after some experimentation probably an 066 and 3120


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There is plenty of room on them. Keep the exhaust port a minimum 1mm on each side from the edge of the piston skirt

 

[vquinoveva]

There is plenty of room on them. Keep the exhaust port a minimum 1mm on each side from the edge of the piston skirt

Awesome thank you


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[Chris-PA]

As long as they don't break through......

Don't forget to look at the piston to make sure it doesn't have features that conect the ports.