The problem with the KQ is that unless you have it snorkeled and you play in the mud or water, you must drain the belt housing. The factory snorkels allow water or mud to get in from the rear, specially if you stop. If you play in the mud without the snorkels, you must take the clutch cover off and get the muck off the clutch. The drain is to the left of the foot brake underneth. Just pull that out, and allow it drain. While draining, press the gas, and rev it up while in neutral. You can drive around on dry ground while doing this, then once its done, put the drain plug back in.
Seriously though, if your going to play in the water or mud, you best snorkel it. Its not that hard at all. If you need help snorkeling it, just let me know and I can get you going.
So 27' tires arent causing the belt to slip, I ran 27 Mudlites for a yr, and before I snorkeled I would notice the belt slipping. I currently run 29.5 Outlaws, but I installed the HL Outlaw clutch kit.