I'd like to chime in with a question for anyone who has already modified their exhaust.
There's some factors to preface my question: I like the original exhaust's look, and don't want to change it's appearance (maybe remove one, but otherwise, the cans looks nice). I also am a welder and want to simply core the exhaust cans out so they breath better (probably sound better, who knows.) So what will this do as far as how the bike runs?
I mean, I have the equipment to do the job sitting around, it's just a matter of time invested. I'm a cheap MF and would rather pay zero dollars. Will the bike run too lean or too rich because of this? The bike is already too lean in my opinion, so if it gets richer, I may be happy about it.
If anyone has some experience on how a TR650 runs with a more open exhaust, I'd appreciate it.
OK...same here.
There's nothing special at all to the Staintunes apart from their superb finish...technically, they're a dime-a-dozen.
(I've cut open a few of them and was agast at what's in them...or rather, the lack of it).
THere's nothing more than an outer tube, 2 end-caps, a couple of hanger brackets, a perforated centre-pipe wrapped into S/S fine-mesh wool (like your 000-sized fine steelwool from the hardware/ household shop) wrapped in turn in S/S "pot-scrubbers" (coarse, doughnut-shaped S/S wool pads)
All that shoved into the outer tubing, weld up the caps, weld in the rear spout and that's it. All components are pre-fabbed and available from exhaust-component suppliers. Outer tubing comes in 20ft length, endcaps, spouts, "stuffing/ wadding" (either fibreglass or S/S wool), perforated pipe and the usual 40/45/50 S/S tubing come in stock length and/ or pre-fabbed.
The "secret" and "mystique" are purely in the mix+match of diameter and lengths of tubing used for inlet/ outlet and the type of perforation of the inner-tube, possible "obstructions" like wedged "nicks" intruding into the gas-flow and the mix and amount of "wadding" used as well as its positioning.
There are some basic physical principles behind gas-flow, speeding up or slowing down flow, creating backpressure or "letting it go".
No rocket-science here...just fairly simple logic.
I used a Staintune 100mm round "made for" an early '80s Yamaha TT600 single.... re-arranged brackets, shortened the standard length of 480mm to a 370mm "stubby" and re-packed the wadding with a little more coarse S/S wool (the pot-scrubbers), increased the inlet from 45 to 50mm and build a fairly sharply curved 18" long mid-pipe from 50mm S/S (the sharp bends created more back-pressure, the bigger pipe created a slower flow) as an under-seat exhaust for a highly-modified V-Strom 650 twin...
The work was done in the home-garage with very basic tools, the welding + polishing done by some pro's in the neighbourhood, materials bought from a custom-exhaust shop close-by.
For a bunch of guesswork and a first try, going by logic and gut-feel only, it turned out an absolute cracker!!
Not loud, preserved the engine braking, sweet pickup, no holes or stutters right through the rev-range, no popping, no farting, punchy down low (straight pull from 2000rpm to 10.500rpm redline in any gear). No Power-Commander, no tweaking electronics, mapping....just bog-stock stuff.
And nothing's changed in 4 years of riding it.
Bought a set of Staintune Ovals for a late Trumpy Sprint ST, cheap, because one had a dent.
Used the good one as was! but increased the inlet from 45 to 50mm again, build a 50mm mid-pipe and hooked it onto the stock 45mm system of another 650 V-strom....another sweet combo doing all the right things without a penny spent on all the bullshyte.
The 2., dented can was again unchanged but opened to a 50mm inlet with a 50mm midpipe for a 650 KLR single.
While cosmetically a bit questionable (as it's now on the wrong side, showing a little of the welding seam underneath the tail plastics), it took 20 mins to cut and re-position the hanger bracket, make up a new rear bracket to suit the bike's existing mounting points, this one shows that for a big Thumpa there's a touch to little "wadding" in the can itself. A little loss of engine-braking (back-pressure), but one hell of a pick-up down low.
Just by feel, the KLR has gained a HP or two, opened up the bottom and mid-range, but at the cost of engine-braking and a little too much noise for my taste (no problem, really...but I like my bikes fairly quiet nowadays...close to stock). Again, didn't change fueling at all, not fiddling with carbs and needles or whatever.
Buy a 2. hand Staintune off any other single or twin (SV650 or so), carefully grind away the weld on the inlet side (so you can re-use the cap), get some more S/S wadding coarse and fine, re-jig the hangers and refab a new 50mm mid-pipe from behind the left frame-strut to the left-hand side rear....or even the right, to keep more bends/ back-pressure in the system. Or keep that as an option, if the left side version finishes up popping and farting/ leaning out etc.
The mid-pipe will be the crux, it's bloody tight in there and increasing the pipe-diameter won't help things.
Use the good one as a sample...I'm in for the 2 one :-))
As for the $$...A$130 for the 2 Trumpy cans with a small box of 45mm Y-pieces and other junk,
A$20 postage, A$20 for 2 new 50mm SS exhaust clamps, A$40 for some bits and pre-fabbed elbows of 50mm pipe, $20 polishing, A$70 for welding and flaring/ notching pipe (all of it in beer)....and lots and LOTS of time and fiddling.
2 exhausts (one V-Strom/ one KLR) A$300, both Staintunes.
THe V-Strom has clocked 20.000km+ without a single hiccup, the same goes for the just recently finished KLR (4000km thus far).
