danssoslow- Im not too sure the temp it starts to burn off at. I know it is a big problem when it welded on as the heat causes the zinc metal to be vaporized and that messes with the quality of the welded joint and it also can make you sick.
If it isnt ground/brushed off, It will smoke a bit. not really good but its outside and your not welding on it. I just quickly grazed a flapper sanding wheel over the pipe to remove the galv. After you finish weld all the joints it will begin to smoke a bit if left in bare steel, cause of all the oils and dirt it had/has on it anyways.
I had also made a oil finish to the pipe as to dull the finish to blackish color. I just heated the pipe with a torch till it was good and hot to touch and sprayed WD40 on it while it was hot. Heated and sprayed, till the finish was good and black. A seasoning if you will...
It stopped smoking alltogether little while after the first heat.
cdoublejj- Hey thanks man, ya I have a few more on my thread. If need any more specifics, I have more, I merely summed up my build here on this forum.
http://www.oldminibikes.com/forum/project-logs/86637-custom-home-built-mini-chopper.html
The sound on my pipe was pretty good. Has a good throaty sound to, a definite thumper sound for sure, un like a v or other twin.
I also put a baffle in the end, it controlled and dampened some of the notes.