I have a 1998 Yamaha SX 700 with about 4,000 miles on it. Should I be replacing the rings, or pistons and rings?
Does it run good? Have you checked to see if the compression of each cylinder is within 10% of each other? I’d say don’t worry about it, these Yamaha triples really provided excellent piston and ring life. Many have 8,000 miles and more with no real need. Sure, you’d get a bit more out of it, but as long as it runs good and the cylinders are close to each other in compression, run it. Most times when these motors are apart with that many miles on them the skirt clearance and ring end gap is still within spec. Wait until you have a better reason to open it up, IMO. The crank bearings seem to go on the ’97s, but Yamaha pretty much fixed that after the first year.