What could I do to a 1990 trailboss to make it faster.It has already been bored twice! It has low end power but not much top end speed.

Tarzan350

 

Add a pipe and a clutch kit to it. You will notice quite a bit with these simple mods. The 250 engine has plenty of parts avaliable. Contact some the Polaris performance companies, I am sure they are more then willing to help. I am partial to RCR ( www.rittercycle.com ), but there are many others. Two other big names are www.hotseatperformance.com and www.hpd-inc.com
P.S. RCR sells HPD stuff along with his own.