What size tires will run good on a scrambler I'm looking at razors?

 

Depending on the type of riding you do 22" XCT's would be a good choice.

 

would 20's be to small?

 

Again, depends on your intended use. 18-20" are usually reserved for MX or applications needing quick acceleration. The 22" will give you a tad bit more clearance and top end. Of course there are other ways to obtain the same results without buying tires.

Just plan ahead so that if you make any mods to the machine you don't end up having to compensate for an earlier decision.