So I had a 1985 ATC 110 with the 5 speed, not many made, had to sell it and now I have one with the four speed, I was wondering if I could change it into a 5 speed? And what gearing ratios should I make it if I'm going to change it, weather or not I am going to be able to make it a 5 speed.

I am going to be putting bigger tires on it, 25" ITP mud lites. I am also boring it and porting the head, performance cam and piston. So I thought I should change it even if I can't make the 5 speed I want.

Any help or input would be helpful
Thanks!!

Also any other sugestions for making my 110 more powerful and more upgrades!