My ole man has a 01 mxz 600, while riding down a trail holding consistant speed around 40mph from time to time the mag side likes to foul out. i have been throu the carbs more than once every thing seems to be in synch. so i did a comp test on it and the mag side is reading 140 and the pto side 160psi wich is about a 12.5% diff where do i go from here all in put is apperciated. thanks :devil:

either run a hotter plug on that side or replace rings in both cylinders before you start in on changing jets in carbs :D

What are you using for oil ? try changing brands and see if that helps.

Ok finally someone has the SAME EXACT problem as me. its about time! the bulletin they have on the 01's fixes that problem. they re-adjust the pilots, and do different needles.