Have a 17MC 163 with the same issues. Only it has a 950 kit in it, so probably even worse. Removed the thermostat and drilled 8 - 3/16" diameter holes around the outer flange to increase coolant flow. Took a chance, but it paid off. Still running scratchers, but that is common in Calif. riding. Using the spring steel scratchers with the flip toggle. Had the cable type, they were a waste of time and money. Pure junk. Running only 50/50 mix coolant instead of our normal 70/30. The 50% coolant mix actually transfers heat better. Also added Water Wetter. All together saw a huge difference. No more uncontrolled overheating. Thermostat is conveniently located at the bottom of the block behind the drive clutch. I mean, what a silly idea to keep it up on top of the head where it has been for many years. After all, who would want that to be a 5 minute job?