I have a 1998 Kodiak 400. Would it be ok to go to a 26" tall radial tire on this machine? I realise I will lose a little power, but I never mud,just trail ride and hunting

 

I had a 350 Grizzly SRA before I bought my IRS version of the same model.
Any how, I had aggressive Maxxis Zilla's 26x9-12 fronts and 26x11-12 rears and the ATV handled them with ease with minimal power loss.

But Zillas are exceptional light weight tires.

 

So the tire weight is more important than diameter? I would think the gearing change would be greater impact.

 

Tire weight is more or the concern then Dia. Here is a good site for tire specs ATV Mud Tires : Best ATV Tires they give you the lug height and tire weight.

Usually the weight increases as the tire get larger and wider, but not in the case of Maxxis Zilla's if you do the home work.

If you compare a 26" or even 27" http://www.mud-throwers.com/inc/sdetail/62/12045 Maxxis Zilla weighs the same as most 25" Tires and they are 6ply with a tall aggressive lug.

Example a Zilla 27-11-12 weighs 23lbs as appose to a smaller thinner ITP Mud-Lite XTR Radial 25-8-12 is also 23lbs. http://www.mud-throwers.com/inc/sdetail/6593/3162 and with a shorter 1" lug. There same size 27-11-12 is 35lbs.

10lbs differance per wheel is large on a smaller 350-400 displacement ATV.

 

If you don't really need the extra ground clearance, I'd stick with a tire the same diameter as stock. The Zillas are a very lightweight tire but yet still 6 ply rated, just get a set of those in the stock 25" size, they'll be cheaper too. I'm assuming your current tires are pretty worn out so upgrading to new tread in stock size will make a huge difference. The Zillas I believe are the lightest 6 ply tires you can buy. You shouldn't notice any difference in performance over the stock tires if you keep stock size.