Tracker takes a turn

01 Feb 2018

Animism aside, it strikes me that custom bikes like to build themselves. You start off with an idea of what you want, and as the build evolves the bike nudges you towards the form it really wants to take.

The XR600R tracker project started with a pretty clear plan: a monocoque body, no obvious rear subframe, and a street-fighteresque visual void between the engine and the rear wheel.

The world really doesn’t need another tracker build with a ‘70s trail bike tank and fibreglass Harley XR750 seat tacked onto it (no disrespect intended, some of ‘em look pretty good, it just wasn’t what I wanted to do), so hours were spent looking for an appropriate ‘flat bottom’ tank that would fit snug to the headstock and pondering tailpiece styles.

India supplied the tank in the form of a repro Norton ES2 unit, and the tailpiece/seat solution turned up at the local tip shop (it’s a rural Aussie thing, don’t knock it) with a banged-up rear fender off a Yamaha cruiser. Bit of work with the cutting wheel, some exercise with the oxy, and things were starting to look good.

Then came the deus ex machina moment. No, not those guys, more of a mix between the classical god-from-the-machine meaning and the meme of a plot twist where a problem is resolved by an ‘outside’ event.

I liked the shape of the seat so much I thought I’d flop a fibreglass mould off it for possible future use. After a bit of dicking around with plaster of Paris I popped out a fair fibreglass version. It needed ‘finishing’ but, more importantly, it highlighted some flaws in symmetry that would need fixing on the steel version.

In the meantime, slotting the steel seat/guard unit and the tank together for a trial fit over the frame showed up some aesthetic and practical issues. While the tank looked absolutely spot-on from the side, it was a tad on the wide side from above and the curve between the tank and seat was (while attractive) a little too ‘pinched’ for monocoque integrity without reinforcing.

One thing, of course, led to another. With fibreglass mat and resin hanging around it was no real biggie to bang out replica tank halves, try a visual ‘cut and shut’ and see if we were on the path to what the bike wants to be.

Certainly looks like it from the photo. There are a few engineering issues to be resolved, but it’s starting to look like they’re going to be easier to solve with composite construction than they would be with steel.

Like I said, I’m starting to believe that bikes (and cars) provide their own guide to how they should best be built….or maybe I’ve just spent too much time in the garage breathing in resin and paint fumes.