i got me a 1980 yamaha specail a year ago. it just seems to lowed geared. even in 5th gear it seems your running high rpms. i just wondered if there was anything i could do to make it a little higher geared. i hada friend tell me to put a bigger tire on the back. its got th 130/16 tire on the back. i just dont know if i did change the rear tire what size tire to go with. can u do anything with the shaft drive to change it like u can do with sprokets?