This is one of the things i learned... The stock Grizzly / Kodiak have a specific internal gear ratio that is fixed inside the mechanical transmission that we cant change. When going to a bigger diameter tire you are effectively gearing the ATV up for more MPH and the engine does not produce the power it needs for that big of gear change. Machining the sheaves will help some but typically you wont bring the gear ratio back close enough to regain stock performance. There is somethings you can do to get the performance back though. Stiffer secondary springs will help a ton in the lower clutch ratio's. I tried that when I went to the PitBull's and before I decided on squaring up my tires. I went from a EPI purple to a EPI Gold and i loved the way my Grizzly accelerated up to 40-45MPH. After the 40-45MPH it fell flat on its face IMO. So what else can be done?? I will let you know what I tried and it works but it will cost you MPG's. I went back to the EPI purple and went to 16.5g clutch weights. My performance was back from the hit of the throttle all way through top end at the expense of not being to go more than 60 - 65 miles on a tank full of gas. Depending on how you are going to use your ATV this might not be a deal breaker??Yeah, im still workin on it. I chatted with Arnie about what to expect and he said unfortunatly no amount of sheave work will get my Kodiak to even feel stock let alone more than stock once I put decent mud tires on it (i was thinking maybe 28 aztex at 35lbs each)
For me it was Not as a lot of times we run between 85-95 miles before we can get gas again. Stiffer secondary springs will slow the clutch shift out point. This helps with throttle response and acceleration but usually at the cost of top end. Lighter clutch weights let the engine rev up faster and could over rev. A slightly heavier than stock secondary spring and lighter clutch weights will get your performance back but at the cost of MPG. Getting your clutching exactly the way you want it can be done though, It will take some time and money for parts to play with. It will take a 2 to 3 secondary springs and 2, 3, maybe 4 sets of clutch weights. Getting you clutchs to the 90% of the way you want it takes time. Getting it to 100% the way you want it turns into work as it takes a lot of time as you have to test each set up in real world conditions. All of this and you end up with 30-40% less MPG. So the choice is yours.
IMO the 1st thing I would do is get your machined sheave and slap in a EPI secondary spring and go ride it. Then make your evaluation if you are happy with the performance or not. If not you now have a better understanding of what it takes to get it there.