Here are some images of the bikes, it looks to me that the 200cc has 17” with a heavy tread patterns and the 250cc does not….the one online merchant site has the tires sizes on both as 21/21 which is obviously not correct.
200cc
https://farm5.staticflickr.com/4229/...e7e21fd9_b.jpgxf200-sm by mjhirz, on Flickr
250cc
https://farm5.staticflickr.com/4282/...94f55359_b.jpgxf250-sm by mjhirz, on Flickr