"Royal ENFIELD Diesel have a max speed of 62mph .... but only 1liter for 70km"
Really? I could believe the second part, but the first sounds like a bit of a stretcher. How long could it hold that 62mph without grenading?
Here's one that sounds a bit more plausible......
http://west.gian.org/node/165"Description:
The innovator has developed a unique, lightweight and compact 3.5 HP, single cylinder, 4-stroke diesel engine with many significant facets. It is compact, portable, powerful, lightweight and affordable diesel engine with varied applications. The engine was mounted on a Rajdoot motorcycle, which achieved an average speed of 55 km per hour and fuel consumption of 100 km per liter."
An average of 55kmh sounds a lot more realistic.
So, I guess you could get more underpowered, but not by much.
Danged crazy furriners..Happy trails.