Wednesday, 2 March 2016

The XS400 RatRacer (part 1)

Now the story started with me and a mate wanting to go back to the track and race in the German vintage roadracing series called Grab the Flag. As it is quite often with such endeavours one person dedicates more time to it than the other. In short: it fell through and this bike had never been raced so far. (I am not strictly a fourstroke or XS guy on the race track, I much more prefer the simplicity and tuneability of an old two-stroke, e.g. like a RD250/350)

Anyway, you're probably not into me ranting about a thing that never came to play, so better tell the story how it started. My good mate Andy knew about a dead cheap XS400 SE that looked like it had been chewed up, partially digested and spit out again.  The only real point in its favour was that Andy had done the engine and knew that except for the kickstart mechanism, which was missing a few parts, it was all there and checked over.

In all its glory
After removing all the rather hideous stuff that turns a XS400 into the SE-model and fitting a pretty lovely 2A2-fuel tank and some longer shocks, which I took out of my Kawa Zed spare parts bin, it looked a whole lot more racer-ish.

Heaps better, but still rubbish
One of the biggest differences between the SE and the stock model is the fact, that a stock XS400 has got an 18" rear wheel with a disk brake and the SE sports a 16" wheel with a drum (which by the way fits perfectly on a Velorex 562 sidecar!) So a bit of shopping on you know which website was necessary and I came into proud ownership of an 18" rear wheel, a correct swingarm and some other bits.
18" wheel in
Unfortunately (as it turned out later) the swingarm bearings on the "new" XS400 swingarm were completely and utterly dead, so I ended up cutting off the brake-torque-arm and mount from the SE swingarm's underside and welded it back on on the top.

Now there's no point in trying to achieve anything performance-wise on a XS400 with the stock carbs. It's just not worth it. So I found myself a nice set of flatslides out of a snowmobile and re-spaced them, so that they would fit on the inlets.

With the carbs tackled, the next step was to make sure how to get fuel into the carbs. This meant knocking up an adapter for my favourite fuel taps - Guzzi, Ducati (and lots of other pasta rocket) M16x1 fuel taps. They flow nicely can be overhauled simply and are dead cheap new.

These adapters are dead simple as you can see: Just a bit of aluminium roundstock turned to 16mm with the afforementioned M16x1 thread and a pressed (and in this case epoxied) into the backplate that mounts to the fuel tank.

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