08 800 h.o tires ?
 

I got 14" rims what the biggest tire I can but on ? I want 28" thanks

The back usually have lots of room to spare. But you should just measure to make sure have the clearance to spare.

Just dived the new tire size height and width by 2 since only the inside and top clearances matter , not the bottom ground and outside clearance which will never rub anything.

Probably need spacers to clear up front but they will fit.

They be IPT type 8 wheels

Your choices would be:
EFX MotoGrip Radial, Kenda Bear Claw HTR,
or lighter ITP Mud Lite XL, ITP Mega Mayhem and Maxxis Bighorn Radial
Compare them here 4WOL ATV Tires
Definitely spacers for front.