Installing an SRX 600 oil cooler
The Yamaha 600CC engine isn't what I'd call a great design. The weird twin-carb system, a penchant for the eating of 5th gears (fixed by running >4/5k rpm, I believe later versions of the engine improved lubrication), sub-optimal head design, , the plain and simple fact that it's an air cooler thumper. It seems to run rather lean too. There's a good reason the later monoshock models came with an oil cooler, this thing gets hot and needs all the lubrication it can get.
Although the great guys at Kedo sell an oil cooler kit, it's a bit expensive for my tastes. Instead, I picked up a second-hand XT600 oil cooler for 25 euros. I don't believe it's an OEM oil cooler, just a generic one someone, at some point, used on an XT. I was hoping to use the oil lines that came with it, but they didn't really fit anywhere in the SRX's feed system.
After a quick clean and respray, mounting the cooler was pretty easy. Even my first-gen 86 SRX comes with oil cooler mounting points at the front of the frame, all that was needed was a strip of scrap metal with the proper holes drilled. I used a tie-wrap to secure the tachometer cable to a hole in the frame to keep it out of the way.
Hooking up the oil feed, though, was more involved. Early versions of the 600CC engine come with feeds for an oil cooler at the front of the crank case (on later models these holes are missing); I decided to hook up the filter there instead of in-line with the oil tank as it would keep all the standard oil lines stock. The holes in the crank case use M14x1.5mm thread. After searching half a dozen DIY and automotive parts stores, I couldn't find any fittings for that thread type at all, and asking about oil lines at an auto parts store, apparently, just gets you blank stares. Thankfully, Hansa-Flex, which specializes in hydraulic accessories (think diggers), carries light-duty materials as well and they were able to sell me adapters, fittings, hose clamps and a couple of feet of oil line.
The final trick is to replace the bolt shown below with a slightly longer version, I think I used one of 16mm in length. This blocks off the direct connection to the oil filter and routes the oil through the cooler instead.
After installing the oil cooler there'll be a large amount of air in the system. To bleed this start the engine, open up the screw/bolt (using a screwdriver instead of a wrench will ruin the thing) on top of the oil filter housing, and wait for oil to pour out.