A clutch kit is overkill. As a matter of fact it is purely profit to the company. You can get all of the stuff in a clutch kit way cheaper if you buy it seperate off eBay. At most you'd need a little shim. 1mm and you will gain all you need back. Anything more is simply performance. Now, a shim is an extremely cheap mod, however you will lose a little top end. Personally. Don't even worry about it. Get the new tires and wheels, put them on, and see how you like the performance. You should be just fine without any clutching. Will you loose power? Of couse, that's a bit more weight. Will you be appalled by the power lose? Probably not. If you want a little more low end, shim it, it's only $8. You probably have that in your pocket right now. I am going to put 26 inch tires on my 660 soon. So I ordered some shims for it only because I can't leave anything alone.