So cast alloys are not heat treatable ?? Good to know.
I figured out that for production purposes it may be cheaper to build a heavier frame not heat treated.
The more I look at it the more I see benefits to reinforce some parts of the frame, that swing arm really looks like it could use some stiffness.
For those who did, how is the ride now ??

Looks very nice. Makes me want to brace mine as well.

am I wrong in my admittedly superficial understanding of these things? but I thought to properly weld to reenforce a frame required the frame to be placed into a jig to ensure no shifting during the heating of welding, or you could lose as much as you gain in other areas? Am I just stuck in the steel frame era?

thats why i braced mine with the engine still firmly mounted.

You could just tack weld it and let it cool, then weld in small passes, letting the heat spread in the piece or letting it completely cool between passes, it should stay straight.

So we are talking about sideways movement, up/down or both ??

twisting i believe.

right I thought it was unpredictable and based on whatever stress at rest was present and could allow movement when heated

That is correct due to the porosity inherent in the casting process caused by small air pockets that get trapped during the cooling process.
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Yamaha Yx600 Radian History