QJMotor Plans… A Supermono Engine?

Cycle World and Euro magazines are running patent drawings showing a weirdo single-cylinder engine design from QJ Motor. Note the smaller-sized rear cylinder, which is solely there for counterbalancing purposes. IMAGE CREDIT: QJ Motor patent

QJMotor might not be a name that everyone in the moto space knows, but if you’re in the know, you’ve heard of them. They’re the Chinese company that bought out Benelli, now building that company’s bikes, and they also build Harley-Davidson’s X350 and X500 models that are sold overseas. But what they aren’t known for, exactly, is developing their own outside-the-box designs.

That might be about to change. Sort of.

According to Ben Purvis, writing for Cycle World, QJMotor is working on a new single-cylinder engine with a “crippled” cylinder. In reality, this is actually a V-twin engine, but while the con-rod and piston in the rear cylinder are reciprocating, they produce no compression; they’re only included for weight, acting as a counterbalancer.

Some readers might recall that they’ve seen something similar before. This is a┬ádesign similar to the Ducati Supermono, the Italian company’s ultra-successful (on the track, not in salesrooms) single-cylinder racebike from the 1990s. Back in 2019, Suzuki filed a patent for a similar idea as well; that’s gone nowhere that we’ve heard of, but knowing Suzuki, it may still come to market in a few years. They don’t rush things in in Hamamatsu.

That big hole in the piston stops the rear cylinder from building compression. IMAGE CREDIT: QJ Motor patent

As Purvis points out: Ducati’s design was different, as the “slave” cylinder didn’t have a piston, just a con-rod connected to a linkage for mass. Still, some naysayers will accuse QJMotor of ripping off Ducati’s idea, but is that really fair? Ducati themselves aren’t doing anything with the idea (their new 698 Supermono is a modified V-twin, but the second cylinder has been completely removed). The Supermono came out about 30 years ago, so if someone else wants to derive inspiration, bully for them. It’s not like any other manufacturer on the market today hasn’t borrowed good ideas from their predecessors (and sometimes bad ideas, too).

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