I'm truly suprised that the English gov't will allow you to run open. I thought they were pretty tough on that stuff.
If you are running a stock, or near stock motor, up to 93", you will get more out of your motor with a somewhat restricted system. Look at hustlers or twisted's exhaust.They got it right.
I've always been a big fan of the SuperTrapp 2into1 system that you can add diffuser plates for less restriction, take the plates away for more restriction. You can tune the exhaust to your motor. And it sounds great. And the neighborhood whiners don't snivel.
The problem with open drags is that people run the wrong diameter, and length. For a shovel, 1 3/4" pipe and 39 to 39 1/2" long. The length is the key. You can buy the 1 3/4 all day long, but dyno time dictates how long YOUR bike wants it.
After 93", open stepped exhaust ,1 3/4 to 2 1/4" diameter, and up to 39 1/2" long works. One has to assume that if you have the larger stroker motors, you had it professionally done, a G carb or equivalent, reworked heads and associated cam and a 10:1 compression +/-. Your builder should also know how to make, or where to buy, the proper exhaust.
Exhaust opinions are like oil opinions. These are where I got my best results. I am a big dyno fan. I'm fortunate that my builder knows how to tune, and build. It gives you a edge.
Last edited by AlCherry; 12-15-2012 at 06:24 AM.