also....what is the top speed of one and what are some mods to do to it under $300??

 

They do mid 60's with stock gears and tire size. Most mods that can be done to them are under 300$ individually because there are not too many major mods out there for the 85-86. I would start with an aftermarket pipe. I had the head shaved .010" on mine and got an impressive power gain for such a cheap mod. Also gives a noticeable gain if you take off the airbox lid.

 

The best bang for the buck is to look on ebay.
FMF pipe-$75-$125
If you don't see many wet conditions, remove the lid or the whole air box and put on a K&N filter. $40
Keihin carb. I run a 35mm and it is great. I have porting done to my bike, so I want to go up to a 36mm. $75
Porting-Some may or may not recommend this, but I found a guy doing porting on enay for $80. It may not have been the best port job, but I could tell the difference. At the same time he shaved the head.

If you shop around, you can get a lot done for $300. Also, remember that you can resell all your old parts.
I once bought a Durablue axle on Ebay for $100, and sold my old stock axle that had a slight bend for $110. So I made money by upgrading. Go figure