Will the two-stroke engine return after all?

Italian Motori Minarelli has now presented a 300cc single-cylinder two-stroke that meets the Euro 5 emissions standard. The cube is intended for use in motocross. Because the emissions meet the currently most stringent requirements, homologation in a street engine is also possible.

Return of two-stroke engine?

So in effect, that seems to open the gate a bit again for a return of the two-stroke engine. Motori Minarelli attributes a power output of 50 hp to the 300cc in racing trim. For the sake of longer-term reliability, the power output will be lower when used in a street bike.

Supplier for Fantic

But will there ever be a street bike with a two-stroke that meets Euro 5? Motori Minarelli cannot answer that question. The company, which will celebrate its 70th anniversary in 2022, is currently primarily a supplier of engine blocks. These include Fantic, the brand that concentrates purely on crossers for competition use. Furthermore, Motori makes Minarelli blocks for scooters.

Technically ingenious two-stroke technology

The 300 cc is a piece of engineering ingenuity. In fact, it is quite a job to keep the combustion in a two-stroke clean. The block was developed in collaboration with the Technical University of Modena. Everything was thrown into the struggle to keep the gasoline from mixing with the lubricating oil. This is a must, as it is precisely the blended lubrication common to two-strokes that causes the burdensome emissions and exhaust smoke.

High-pressure injection

In this new 300cc, gasoline enters the combustion chamber via high-pressure injection. The rotating parts are lubricated with pressure lubrication, and the piston scrapes the oil along the cylinder back toward the crankcase, just like in a four-stroke engine. After all, fuel injection eliminates the need for coil ports. Exhaust gases go to the exhaust through a variably controlled exhaust valve, as in a four-stroke.

Tested in enduro

Meanwhile, the block has already proven its services and qualities in enduro racing. Riders, according to Motori Minarelli, raved about the power and especially the punchy throttle response at lower revs. The lack of pulling power in the lower reaches of the rev range was always the Achilles’ heel compared to the four-stroke engine. So with the Euro 5 block, that problem seems tackled.

Also plan for 50cc two-stroke

Motori Minarelli also claims to be working on a small 50cc two-stroke block that is Euro 5 compliant. There will certainly be interest in this among a number of manufacturers. Especially among the makers of light scooters and mopeds with internal combustion engines. In a number of markets (in Southern Europe and Asia), the enthusiasm for gasoline-powered light motorized two-wheelers remains strong because the charging infrastructure for electric variants is not (yet) in place.