I'm just leaving it as is with the internal oil passage way open. Even putting a restrictor in makes me nervous. There was no real easy, safe way to block it off and keeping it open allows me to isolate the cooler with the engine running and use the sight glass to check on the oil level. Took a while to figure that out, might put a ball valve in the "to" line instead of clamping the hose with vice grips. Think a ball valve would be a good idea, then you could isolate the cooler in cold weather. An automatic temp controlled bypass valve would be cool to have but there isn't a lot of room to work with, there is a big ol exhaust pipe in the way. I was a bit nervous about welding onto the downtube of the frame so ended up using hose clamps to attach the brackets with. Thinking about shooting the cooler and brackets with some rattlecan black paint to hide it when I get the time.
Can't get out to ride for a few days, my wife has a real bad ear infection and it looks like I'm elected to
keep an eye on her till the fever breaks.
Oh yeah, a big thanks to Lancer, couldn't of done the cooler without the oil flow diagram he posted on another thread.