The Two-Stroke Returns?

There are reports out that General Motors is working on an updated two-stroke engine, news that tickled my fancy when I read it.

My challenge now is to tickle your fancy, and make the story interesting. This is something my eight-year granddaughter failed at intentionally during a visit earlier today when she offered to tell me a story: “Once upon a time. The end.”

This was her joke on me. But, as much as the two-stroke return might seem to be a joke, too, the story seems to have some legitimacy.

I will ignore the reality that the story I read had a blatant factual error in the first paragraph, that gaffe being the claim that a two-stroke “is a type of engine not seen in cars (outside of the old Soviet Union) since before JFK was elected president.”

Not exactly. Swedish auto maker Saab (located beyond the former Soviet Union) sold cars with two-stroke engines as late as 1967. History buffs here might recall John F. Kennedy was elected in 1960 and assassinated in 1963, both before 1967.

Regardless, it is interesting to read of a two-stroke revival, which according to the story would provide cheap internal combustion ability to recharge electric vehicles’ batteries on the move.

Two-strokes these days mostly are the province of off-road motorcycles and chainsaws, favored for their simplicity of design and their high ratio of power to cubic-inch displacement.

Two-stroke engines have no valves to allow fuel into the cylinder or exhaust gasses to leave. That is accomplished by holes (ports) in the cylinder walls.

This means a two-stroke engine produces power every other stroke of the piston, while a four-stroke engine has intake, compression, combustion and exhaust strokes, with only the combustion stroke producing power.

The difference is notable. In my wild and crazy youth, I owned a 1970 Kawasaki 500 with a two-stroke, three-cylinder side-by-side-by-side engine.

Out of the box, these were low 13-second machines in the quarter mile. But the previous owner, unbenown to me, had ported this bike for drag racing and it easily was a 12-second bike.

The torque at high rpm was incredible. It took off like a rocket at 6000 rpm and beyond. I recall the days as a freshman at UPJ when between classes I’d ride with friends who had motorcycles, including a 750 cc Honda. I’d leave them in the dust on Schoolhouse Road in seconds.

But there was a compromise. My Kawasaki, perhaps owing to the porting, fouled spark plugs at an incredible rate. I actually carried extra plugs and got to be quite good at popping the gas tank up and changing that middle cylinder’s plug.

I traded in the Kawasaki when I bought a new 1974 Yamaha 500, a much more sedate four-stroke example. Sure, it was a lot slower, but it also was a lot more reliable.

Part of the two-stroke experience is oil is mixed with the gasoline, which makes it almost impossible for them to meet emissions standards. My Kawasaki had a separate oil tank and injection pump for that purpose.

But, early two-stroke Saabs required the driver to add oil at each gasoline fill-up. This provided some amusement for a distant relative of mine during the gas thefts that accompanied gasoline shortages in the 1970s.

While many took to slapping on locking gas caps in an era before that was common, this guy welcomed would-be gasoline thieves, who would be getting more than they bargained for by siphoning out his gasoline-oil mixture.

Ah, memories.

We will close this story now with an observation. I find it amusing in an ironic way that the two-stroke engine, relegated to the automotive sidelines due to its dirty exhaust, might prove to be saviors of electric cars, at least for GM.