The Stinkerle (part 1)

Ever since the days, when I did multiple RD engines for some other people, did I want to build a quick two-stroke for a bit of vintage road racing on a budget following the classic Colin Chapman mantra: "Simplify, then add lightness."

Over the last few years I have amassed quite a few left-overs from various other bikes. With the move completed it's now time to have a look at all the parts and decide whether the best course of action is to sell the whole lot and never speak of it again or actually dig into it and build a usable racebike from it.

The engine is the biggest unknown quantity, as all I knew about it was that it was stuck. Better start somewhere else then. 😉

For mere test-fitting the old ball-bearing headstock bearings would have been more than sufficient. But over the years not a single one of the balls stayed where it should, so new tapered roller bearings were the order of the day.

Equally shocking (and a good indicator to the troubled past of this frame): some had already installed a needle-bearing conversion in the swingarm and some grease fittings.

Moment of truth:

Yep, piston seized in bore (what I secretly hoped for) and not a seized crank. And both pistons were in a position, where they more or less close inlet and exhaust ports. The root cause most likely being a combination of the ignition timing being waaaay too advanced and still a relatively tight bore from the cylinders being freshly honed.

Even though someone in the past had already put on RD250 cylinders (this is a YDS7-block) and try his (or her) best to slaughter the engine, the crank still feels fine and rotates freely. It must have been dry and oily down there. So nothing but a good clean up and we should be golden. 

Talking of cleaning... I chiseled and washed off about one to two kilograms of caked on dirt from the engine.

And yes, I went with the ubiquitous RD50 fuel tank. Just a note, it fits nicely on the frame, the petcock has to be moved a bit further forward to better clear a frame rail.

Not sure about the seat hump, it's what I have at the moment and it fits quite well over the frame rails.

So what's the bigger plan: I've ordered some super-cheap 125 expansion chambers, because I don't have any exhausts. I already have a set of mildly worn out RD250 cylinders, pistons and cylinder covers. A set of SR500 front stanchions should come in over the holidays and I already have all the bits for the rear wheel, which are missing in the pictures. The ultimate goal is to stay as close to the 100kg-mark as possible, which currently looks rather doable. Now if I can get the engine to make around 30-35hp with the given carb and exhaust setup this should be plenty enough for me.