So my brother and myself have been experiencing RPM loss, he rides a 163x3 and I have a 163x2.6 after trying about every different clutching combo under the sun with new belts and washing the clutches we finally decided to return them both to dead stock. Both machines seem to be very sensitive to altitude change, losing about 100RPM for 800 ft of elevation change (6400-7200ft). Currently I'm running between 7950 and 8100, the later being difficult to achieve. so we finaly decided to pull the plugs and do a compression test. First off, plugs looked terrible, have an obvious bad burn, half the plug (exhaust side) is way lean and the ceramic coating below the electrode is actually being removed. Then the intake side of the plug is cruddy and fat looking. Anyway compression for mine is: PTO 120 MAG 115 and my brothers is 115 in both. Thats WOT and about 2500ft here at the shop. We also tested a third AXYS that has been running great, its got 125 in each and his plugs look like a plug should. All three machines have about 600 miles on em. I'm going to be talking with my dealer about it, but does anyone have any theories?