AA...is this the quad you want to buy a Shearer pipe for?
If so, I hate to say that you're out of luck for those year models (85-86) because those pipes are only made for the 87-92 250's.
Your best bet is an FMF pipe on an 85-86, though you have more options to have a custom pipe built since it's a standard 2-stroke without a powervalve.
Might even be able to con Matt Shearer into designing a pipe for the 85-86's, who knows...