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Grass Valley, CA
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RandyS
10/25/2016 4:39pm
10/25/2016 4:39pm
I think I might have asked this before but I can't find the thread. I've got a 73 dt250 that I was going to make a vintage MXer out of so I sold off a lot of the parts down to the frame. I decided to make kind of a bobber out of it similar to the one in the picture. I don't have a pipe so I was thinking about taking a few of the stainless 4 stroke stockers I have and having a friend tig up a pipe that would be tucked in and not in the way. I know trials bikes don't have much of an expansion chamber and they're all low end although the FMF Fatty kind of goes against that thought so I'm a little confused. The stock Yamaha pipe didn't have much of an expansion chamber and what it had was at the end so it never really made back pressure like a modern pipe. What would a straight pipe with a silencer run like? It would still have a larger chamber, maybe half the size of the bike below. Also a welder question, would media blasting the area to be welded be OK or is the used stainless going to be a nightmare?
The Shop
It's just gonna have low end, prob won't rev too good, but hey, wtf, you ain't takin it to the salt flats.
I had a 1970 250 Husquvarna back in the day. Very little bulge, stinger the size of a silver dollar, was a stump puller.
It's s bobber, different is good.
Yamaha rds had basically straight pipes. Their power was pretty flat i think.
Can never go wrong with cones.
I dont care what its on.
Pit Row
The factories had taken Walter Kaaden's 2t tech and had run with it, for well over a decade by then. An expansion chamber doesn't have to look like one of the glorious examples pictured above, to be, nonetheless, an Expansion chamber. Even the flattened bulge DT pipes you describe were still a form of expansion chamber, just as 2t Trials bikes pipes are. A 'box', is still an Expansion / Helmholtz chamber. They are just made for different effects / levels of performance.
Hell you could probably put just about any type of chamber, suitably cut to fit the bike, and it would work better than a straight through, or divergent coned only pipe on a 2t. My Californian boss in the 70s, who started Australia's then version of DG / FMF / PC, = Competition Development, called those things 'bluey pipes', and regarded them with absolute disdain. Go to a wreckers, and find a few pipes to play with, if you won't have a proper pipe made. Oh, and by the way, said 'bluey pipes' are the most disgusting sounding exhausts in the universe, well, other than straight through HD pipes............ ride something like that, and you'll be a deserved object of ridicule, and, probably be quickly locked up, to boot.
https://m.youtube.com/watch?v=_pK6Hq3zz0U
Got told horrible story once bout a Tree Surgeon who had accident, ever since been very very dubious of chainsaws!
Sweet little bike BTW.
https://www.amazon.com/Two-stroke-Tuners-Handbook-Gordon-Jennings/dp/09…
This was/is the basic primer for you smoker tuners.
Hey, I met my old lady when she had a Methanol burning extended swingarm 10 paddle Taller Hauler overbored Banshee on nitrous.
It had Chrome stinger pipes. No silencers. It sounded sooooo good.
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