For its latest YouTube release, the Purpose Built Moto team is getting its hands dirty with taking a tired and beat-up Yamaha XS650, cutting it in half, then rebuilding it as a slim, sleek and lightweight street chopper. Principal Tom Gilroy is looking forward to watching the tools and workshop perform.
The tick list of major mods on this project include:
• A 700cc race engine
• A lightweight, chromoly hard tail
• Upgraded front suspension and brakes, AND
• A suspended rider seat.
The Yamaha 650 twin is a much-used and highly regarded engine, with excellent reliability and great potential for power output. With these mods we’re aiming to drop 20kg-30kg off thebike’s weight, which will ultimately provide a lively ride.
THE TEARDOWN
After moving into our new space (see issue #74 – Ed), we had seriously tooled up. With a huge delivery of SP Tools roller cabs and toolkits the week before, we were itching to get to work. Our motorcycle bays have been kitted out with the SP Tools Custom Series roller cabs with lockers and the tool kits to suit. The toolboxes also left us a bunch of room for the Makita cordless grinders, drills and chargers.
Because we’re not an in-and-out oil-change shop, most of our projects require some form of fabrication or modification.
That means we need workbench space. The SP Tools low-line cabinet is perfect with its tool storage underneath and a huge workbench on top to work with. The set up for us is a lot better than the top-box set up most mechanics use.
Our tools were broken out, the bike stripped bare and an engine jig fabricated to make sure nothing critical moved when the frame was chopped. We used the engine and engine cradle, and the rest of the bike was scrapped or sold off for parts. That’s just how far we’re going with this build process.
FRAME FAB
The bike went into the fabrication room to start its surgery.
We’ve fabricated a frame jig of sorts to hold the frame and rear axle in place. This was built to sit on top of our steel-fabrication jig table, an epic addition to any workshop. We’ve custom built this set up so it can be rolled around the shop and used for everything from sissy bars to fender mounts. This time around it’s frame fabrication.
You’ll notice our fabrication bay isn’t some sprawling open space. Room is always tight at the shop so we try to use it wisely. We’ve managed it pretty well, and all our key tools are within arm’s reach. Having two of us working on the same bike definitely gets a bit tight for space, and using cordless tools saves a lot of crossed leads on the floor. The Makita kit is stashed under our fabrication table and a few charged batteries kept on hand.
With our donor frame mounted securely in the frame jig, Dylan and I got busy making measurements and planning out our hard tail.
Shortening the wheelbase slightly and reducing the tube size would really bring out the short, sharp, look I was after, and we used a 2mm-wall, 19mm-diameter, 4130 chromoly tube for the frame. With our static points set and the new wheel/suspension sizes mapped out, we started designing how the frame would look, linking the existing frame to the new axle location.
GETTING IT RIGHT
For this project we’d upgraded our bending set up, too.
We do a lot of solid-bar and tube bending through our custom projects. For the solid bar we have a very simple and very cheap ‘tube’ bender. It comes with dies that range from 8mm up to 25mm in various radii, and although we never use it for tube bending it’s perfect to bend our smaller round bar.
The big upgrade we’ve just got is a Speedwerx mandrel tube bender.
Australian made, and with dies made to order, this was by far our best investment after moving to the new workshop. The ratchet-style linkage makes it easy to bend the super-strong chromoly tube we use in sizes well above what we will ever need.