Missing Two Strokes

  • June 21, 2024

There’s only one kind of gas-burning engine we’re allowed to have, which is a shame for reasons that go beyond the obnoxious effrontery of being told what we’ll be allowed to have.

The engine type we’re allowed to have is the four stroke engine.

There is nothing wrong with this type of engine. There is a lot to like about this type of engine. But there is a simpler type of engine that has many fewer moving parts, that makes more power for its size and – like a diesel engine – uses its fuel as a lubricant, which serves to keep the wear-parts within it from wearing sooner rather than later.

It is the two-stroke engine.

This type of engine generally does not have a valvetrain; i.e., it does not have a camshaft, intake/exhaust valves and all the associated small parts, such as springs and retainers. Instead it has ports – which are basically just openings cast into the cylinder that are closed (and opened) as the piston moves up and down during its stroke. These ports don’t move and aren’t themselves subject to wear and tear, unlike valves, seals and springs, etc. They also double the power made (all else being equal) by adding a power stroke to the combustion cycle. A four stroke engine only makes power once – during the power stroke. The other three strokes – intake, compression and exhaust – are just the before-and-after the main event.

Two strokes are also lighter – by dint of not needing the extra parts – and more compact in size. They are much easier to work on when repairs/maintenance are needed because there is much less to work on.

Or that might need work.

So why can’t you buy a two-stroke engine anymore?

Well, you can. Just not in a street-legal vehicle. Two strokes are still the go-to engine for chainsaws and small outdoor power equipment generally. Precisely because they make a lot of power for their displacement and because they are simpler and so less expensive to make (and buy) than four-stroke stuff.

You used to be able to buy motorcycles with two-stroke engines – and you still can. Just not street legal ones. Those have been out-regulated (as distinct from outlawed) for decades. The distinction is important because it matters. Laws are passed by elected lawmakers – who are at least subject to elections. Regulations are imposed by bureaucrats – who never have to answer to voters. Things that might be hard to outlaw are easily out-regulated.

And what are you going to do about it?

That’s what happened to two-stroke-powered street bikes, which were once very commonly available due to all the two-stroke engine’s strengths. A fine example – a series of examples – being Kawasaki’s line of two-stroke powered street bikes that once ruled the streets. I have one of these bikes. It is a 1975 S1, which is powered by a small (250 cc) three cylinder two stroke that makes about twice the power of a two-stroke single of the same displacement. But the big Kahuna of the line was the infamous H2 750. Same basic bike plus 500 cc more engine. It was affectionately – and respectfully – known as the widowmaker, on account of its abundant horsepower that came online very suddenly. One moment, you’d be looking at the road ahead; the next, you’d be looking at the sky above.

This was hooligan fun, assuming you knew how to handle it. Some didn’t – and hence the name (and respect).

The point, though, is that this very quick street bike was also very affordable; almost anyone who dared to ride it could own it. Never before had such high-performance been so accessible. The H2 – and even its slightly less ferocious sibling, the H1 500 – were the performance equals of four-stroke superbikes of the same era, including Kawasaki’s own Z1900 (I own one of these also) that were not very affordable. The Kaw 900 is a more sophisticated performance bike – but what good does that do you if you can’t afford it?

Luckily, there was an alternative to it.

But that’s all in the past now.

Two strokes for street bikes ran afoul of the regulations back in the late 1970s and by the early-mid-1980s, they were relegated to off-road bikes (and outdoor power equipment).

Some will say, good riddance! Those two-stroke bikes smelled! They left clouds of blue smoke in their wake! And – god – they are so awfully loud! All of which is entirely true – and also part of the charm. If you’ve ever heard one of these rippers cut loose you either know it – and love it – or you are one of those people who can’t stand it.

In which case, you’re probably one of those people who thinks engines you can hear are manifestations of psychopathy. As opposed to the sound of being alive – and enjoying it!

. . .

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