Friday, 12 May 2017

Exhaust-building - Mk.7 2in1 exhaust

There's a German pro-verb, that Spring will occasionally bring in something new. I've built, modelled after the equal-header-length 2in2 Mk.7, a 2in1 with headers of the same length. This one is meant to go on a XV750 and I am really, really curious to see, whether the smaller header tube diameter will yield the benefits in low-end torque.

It's not exactly the first XV-exhaust I've built, but I decided to change and try out a few things, based on what worked on the Guzzi and what gave me headaches in the past.

Firstly I had bigger flanges cut, which still don't do away with the need to use exhaust gaskets, but will seal a lot better as they are a snug fit into the head and it cures potential misalignment and shifting during welding.

I used an old lathe chuck this time to have the rings sit REALLY perpendicular to the tube.

The second added bonus of doing small inserts for the head, it's a lot easier to measure the downtubes as you have a fixed datum to work from. 

Tube fitment is the one big thing when TIG-welding. Every minute you spend on fitting up the parts will come back to you at least double, when welding. 

I admit I have been a tad too careful with how much I cut out on the inside...

... which meant attacking the innards with a carbide burr on a die-grinder for approx 90 minutes and then buffing everything up with a mini flapper wheel. 

The time when parts take shape. 

And that's what I ended up with: once on the bike 

... and on the bench.

But don't worry, this one is not meant to go on my everyday TR1, but on a different bike... Actually I plan to re-do the Mk.7 from the everyday TR1 in Summer as I've improved the design in various areas (mostly fabrication-wise and a bit in fitment, I think) and I need a second Mk.7 anyway to be used with the supercharged TR1...

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