Thanks for telling me this bit about history. I never thought exhaust would be a problem. Now I see how it could be one.
A comment on the subject of annealing aluminum during welding. Years ago I was witness to some aluminum chassis fabrication. The frame and swing arm were sent out to be "pickled." As best as I know, the chassis was retempered by immersing it in a hot liquid. Bradley in his book "The Racing Motorcycle" Volume 2 gives a lot of advice about welding and retempering aluminum alloys.
Up here in the woods it is hard to get good advice about anything related to racing. I read books and magazines to learn. This was easy when Borders Books was in business. This was a big book store with an in-house coffee shop. I could sit down and browse through books and read the tidbits I needed. They went belly up. I had to find a new method to get books and I can afford to buy only a portion of the ones I need. This is what I do now. An example.
New radial tires are developed with rubber compounds having less internal friction when flexed. Does this reduce rolling resistance? This is what I want to know. First, I look up "Motorcycle Tire" in Wikipedia. These sentences are in the lengthy article. "Rolling resistance is the resistance when a tyre rolls on a flat surface. The rolling resistance coefficients of motorcycle tyres are about 0.02[1]."
The [1] is a link to a reference note. I click on it and this comes up. "Cossalter, Vittore (2006), Motorcycle Dynamics (Second Edition ed.) Lulu.com pp 37-72, ISBN 978-1-430300861-4" THis is the reference note. It describes the book. I copy it.
Now I open
http://openlibrary.org/ This is an internet library. I type the ISBN number into the search box. I separate the numbers with dashes just like on the previous paragraph.
Up pops a few choices. One is a link to a scanned copy. There is not one for this book. I could read it on-line if there was. That sometimes happens.
Another choice is a list of people who sell the book. I click on Powells Books. They are in Portland and if they have a copy on the shelf I can peek inside. They do not. The books are in a "remote warehouse."
A further choice is a list of libraries that have a copy. There is one in Eugene. That is not far from my house. I will go down to the local library, give the librarian the mooneyes, and sweet talk her into getting me a copy on inter-library loan. She does this sometimes when she feels like it.
A fellow can race when almost broke. It just takes some creative thinking.