I'm embarking on the project many of us have thought about
: building a 2 -> 1 exhaust, for the specific purpose of creating an empty space for more fuel capacity.
Ultimately, this post may turn into
because making one may not be much less expensive than making a bunch, in which case I'd start a business to sell them... but since I haven't made any sort of decision yet, it's not spam yet.
In anticipation of questions about that, I started a vendor thread here so that we don't junk this thread up.
I'm lucky to have both an Adventure and Superenduro right now. I'm starting my work on the SE because it was already in pieces, but these same concepts will work on either variety.
First step was chopping up a stock "H" pipe to turn it into a 2 into 1.
Here's the finished product:
I believe that it will be necessary to make a larger diameter pipe past the junction, but I have dyno time reserved this week to find out for sure. I'll be testing the bike full stock, with 2 neptunes (baffles in and out), and with 1 neptune. I won't have time to change jetting between pulls, but I suspect we'll learn something anyway...
Then, I took some styrofoam and mocked up a tank shape.
Used packing tape to attach mounting points:
Glassed the top in to make it a bit more durable:
And presto-wallah, a reartank prototype for the SE:
Ultimately, the shape needs a little tuning, but it is ergonomically excellent (no edges to catch, impossible to feel when on the bike), is out of the way as the swingarm travels, improves the balance of the bike front to back, and will give over 2 additional gallons. Because of the length, I believe that the finished product should be filled with baffling foam to avoid a back to front slosh (or vice versa) under braking.
I've been kicking around constructions for the tank with a bunch of folks over the last few weeks, and it's been an interesting learning experience. The two methods that seem most practical are forming aluminum, and rotomolding.
The advantage of the aluminum option is that the cost for the first might be lower, but I anticipate that it would be easy to dent in a fall, and I worry about the effects of vibration on aluminum over the long haul.
Rotomolding costs a lot to make the first one... but I'm meeting with a vendor this week to find out just how bad the damages would be.
Anyway, I'll report the facts here. I think this will be an interesting one to play out!