does anyone make a top end rebuild kit that includes jug and piston and power reeds?

 

Are you trying to install a reed cage on the 250?! I've never seen a set up like that available but have thought about building something like that many times. Those motors can really rip with some porting and planing the head.

 

HPD used to make a reed conversion for the 250s
But you can get good power by porting the cylinder and milling the head .020

 

If you are really looking to make some power out of the 86 trailboss, look at the 87 cyclone service manual. the cyclone was basically a factory modified trailboss engine. The head on the cyclone has .060 to .080 less squish than the trailboss. The timing is advanced almost as far as it will go and it runs a 34mm carb instead of the trailboss's 28mm. The cylinder is ported much more than the trailboss as well.... These things as well as the correct exhaust and clutching and you should be able to beat some stock 400Ls in a drag race.