Can motorbikes use diesel or petrol?

Answer 1

Because of the higher cylinder head pressure that diesel engines use, if made with the same types and grades of metal alloys, they will always weigh more - and cost more to make - than an equivalent capacity petrol engine. The extra weight and physical size - and cost - makes diesels unsuited for powering light equipment like lawn mowers and motor bikes.

BUT, we have seen recent developments, where electronics has replaced a lot of old wires, fans, belts - nuts and bolts. This has made it possible to make diesel outboard engines with better power/weight ratio than the old petrol engines. This is still at the high end. But it is now fully possible to consider a large motor bike being equipped with a diesel engine. These would get better mileage, and more important, less need to change gear because the diesel engine is able to deliver its power over a much wider span of rpm. It is slower to start, but once it gets going - it keeps on going.

Another opinion

Diesel engines can give great torque at low revs but can't deliver the same wide span of power - going from low to high revs - which petrol engines offer.

Consequently, to get the speed and power range which a motorcyle rider expects to use, a greater number of gear ratios would be needed with a diesel compared to a petrol engine. To have more gears means having a larger and heavier gearbox and having to change gear much more often, both going up and going down the box.

Using currently-available technology:

• the larger and heavier gearbox, combined with
• the heavier engine and
• the extra manufacturing costs of making them both, plus
• having to manage maybe fifteen gears - like a truck - instead of five or six gears

all conspire to make a diesel-engined motorbike unattractive.

Marine engines require quite different speed/power/cost specifications, which diesels can certainly achieve.