Help Rincon Transmission Slipping
Does it slip mainly in high gear at high throttle, when hot?
I wonder if you might have the blown O ring problem that early Rincons are known to have...
There is a procedure for checking oil pressure at 3 different ports. Some folks on Rinconrider fabricated a fitting for an oil pressure gauge, but since it is something the average person would only use once, it might be better to have the dealership run a pressure test.
First, though, verify the oil level is correct. To get an accurate reading the machine needs to sit at idle for about 4-5 minutes, then sit for another 2-3. Oil level needs to be at the top of the range, or just slightly overfull...