Daydreaming about building my own head pipe while I'm sitting here at work. Anyone know the diameter of the exhaust port?

 

Ball park 1-3/8" ID. That is the size of the header I have. I forget if I measured it back when, but I'd think a high performance pipe would be size on size.

If you bought a couple 180 degree mandrel bends you could build one rather readily, especially if you or someone you know has the TIG skills. I did it with a friend, a wizard with a TIG, and some tubing. I used 2 - 180s and a 45 for it, but I think you could duplicate the pipe for the KLX with a 180 and maybe a 90 or the like. I did the calculations and came up with around 21" length, matched up close to the header again (just measured it again). I'd do stainless to avoid having to paint, plate, or coat it.

You can make the collar by cutting a small ring of the tubing, splitting it and welding it on the end. Be sure to have a gasket in the head while fitting. If you don't, any brackets will end up out of position causing fit issues - don't ask how I know.

 

Lots of cheap chinese exhausts for the cr230f in stainless. from what I can see they have a 34mm ID opening up to 38mm which is pretty close. Might try and cut one up

https://www.ebay.ca/itm/Slip-On-Full...53.m1438.l2649

 

https://www.ebay.ca/itm/Exhaust-Head...53.m1438.l2649

Might also be an option with a few tweaks