So I'd like to do a little exhaust work to the bike but have a few questions. I want to do a turn down right where the muffler would hook up with no baffles. My question is; will using a smaller diameter at the very end of the pipe compensate for not having a baffle to create back pressure? If so, what ID should I use in respect to the stock pipes size for optimal Proformance? And, would I just be better off buying a muffler for this thing? I made my own exhaust but I feel the piping is too long and I'm not happy with the way it sounds. If you can't tell by my build its on a budget so cheap suggestions please!!

I see what you're saying. I definitely want some back pressure and I don't want to be replacing valves till after the summer. But if we compare it to a hose it only flows stronger because of the pressure it's building up. So wouldn't a smaller diameter opening create the back pressure I need to prevent cooking valves?

Singles ingest a lot of air in between pulses, so even a small hole on the backside won't solve the issue.  I'd put a baffle at the end of the header and at least a shorty muff on.

Is there any special reason for using brass?

Lucaisrussell wrote on 01/17/13 at 22:22:55:

It is a plumbing part, so you are limited to what is used in plumbing.  Brass is used because it does not rust.  Not a real concern in exhaust, but actually somewhat handy.

Turned down with no baffle will be really loud for you while riding due to reflection off the ground.  I did lots of experiments with intake and exhaust when I had my 650.  Longer will maximize the torque. Having the pipe end about halfway between the rear axle bolt and back of the rear tire maximized my torque. I wouldn't suggest adding anything that would narrow the pipe. I'd suggest straight pipe with no baffle. The full length pipe will add some resistance due to its length but likewise work better with the bikes particular exhaust pulses by allowing the momentum of the exhaust help to create a negative pressure towards the end of the pipe. Doing a slash cut on the end will increase the exit area of the pipe.  I know that is now the look you are going for. Just some info that might be helpful.

Think of the 650 engine as a single cylinder cut off from a 318 ci V8.  Then research what intake/exhaust mods improve that motor, such as effect of intake runner length, long tube vs short tube headers, etc. Much of it will translate over to the 650.