I am in the process of rebuilding my fully ported gp1200 race motor and I am having some issues with some of the piston specs from the manual. I checked all 3 of the cylinders with my bore gauge and they are all with in the specs of taper and out of round-ness that Yamaha gives in their factory service manual. I am just going to give thoese a good hone and be ready to go. This is where I ran into my problems. I started to measure the piston skirt diameter and my measurements seem to be off about 3 thousands in respects to Yamaha's specs. The spec that Yamaha gives is 3.3032 to 3.3040 inches for the diameter. On piston one I get 3.300 on two I get 3.301 and on three I get 3.300. My concern is that this is a significant difference from what Yamaha reccomends and I just don't see how all 3 of the pistons could be off by almost equal amounts. I am using all Mitutoyo mics. to measure this, and I double and tripple checked so I know these measurements are spot on. My question to you is 1.) have you ever heard of this before? 2.) should I replace the pistons?
Thank you for your time!