The engine sizes vary very much with the markets we are talking about. I am living in Europe, here you can say:up to 50 cc: Tiny motorsccoter, usually one cylinderup to 125 cc: Motorscooter or tiny motorbike, usually for those who are too young to get a real motorbike license. 125 cc motorscooters are interesting for elder people who are allowed to ride them with their car license.Real motorbikes which require a full motorbike license usually start at 350 cc, most have 600 cc or more. Motorbikes are separated into two classes, those below 35 kW/48 HP and those above. About all bikes with more than 48 HP have 600 cc or more. In Europe, a "big bike" begins at 1,000 cc, so we are talking about bikes with 100 HP and more. There are also supersports bikes available with 600 cc and 120 hp, but these are not regarded as "big bike", but rather as highly refined sports tools. The best selling motorbike in Germany is the BMW R1200GS, it features a 1,200 cc flat twin engine and 125 hp. It is definitely a big bike with a big engine.

In the U.S. engines are even bigger. The smallest Harley Davidson engine has 883 cc, others have 1.2, 1.6 or even more liters displacement. However, compared to engines common in Europe, these engines are tuned rather to much torque than to much power, most of them have 60 to 90 hp. The biggest motorcycle engine is a 2.3 liter three cylinder engine built in the Triumph Rocket, but this  big engine displacement is quite rare. One can say, that most big engines have a displacement between 1,200 and 1,600 cc.excelsior henderson motorcycle for saleIn southeast Asia, in China and India, things look entirely different. best motorcycle roads finger lakesThe biggest bike Royal Enfield makes has 500 cc, a 350 cc bike is a well renowned middle class bike for middle class buyers. suzuki motorcycle parts lancashire

Most people who use a bike mainly as an affordable tool for transportation stick with 125 cc. European manufacturers like KTM and BMW have teamed up with Asian partners to build motorbikes targeted for the upscale consumers of those markets, and they offer engine sizes between 350 and 400 cc. The smallest BMW assembled in Europe has 650 cc and 48 HP. Harley Davidson has released two models for the Indian market, the Street 750 and the Street 500. Their displacement is fat for Indian circumstances, but tiny according to U.S. standards.motorcycle tires durbanI do not know exactly about all the rules in Asia, but as far as I know, China has banned motorbikes with more than 750 cc, and biles with 400 cc are quite reasonable in Japan. the best 800cc motorcycleSo one can say: Go west and have big engines.      yamaha xs650 for sale in uk

As others have pointed out, the perception of what is "large" has changed over time and depends heavily on your location, as well. I'm in the U.S., and I consider anything over 750cc large, no matter what you're riding. In reality, much of this depends very heavily on what type of motorcycle it is, and its intended usage. For example, 450cc would be considered a large, international competition-ready dirtbike, something you'd consider for the Paris-Dakar rally. shoei gt air motorcycle helmetsA 450cc standard bike would be a rarity, but would be considered a small, sporty all-purpose bike, ideal for commuting. A 450cc sport bike would be considered a lightweight racer, suitable for beginners, but potentially competitive in the right hands. A 450cc cruiser would prompt questions like, "You're joking, right? What did you do, remove half the engine?"Each engine I've mentioned above is tuned with a very different purpose in mind.

The cruiser is detuned for an easy-going low-end torque and a loping cruise. The racer is all about the revolutions per minute, and is tuned to make maximum torque at high RPMs. Each one is changed to give a different character that the designer is going for.I ride mostly in the US and Canada.  There has always been a line in my mind between smaller bikes and big bikes at the 1000cc engine size.  That line has changed over the years, though.  Back in the 60's 750cc was a huge bike.  Today a 600cc sport bike can have 105+ horsepower and a 1690cc Harley engine runs around 75hp stock (rear wheel figures). So big can have different meanings.  I ride a 650cc Suzuki VStrom which I use for around town and for long distance touring.  I ride a 650cc KLR650 which I use for off road touring and for touring within 500 miles of home.  They have the same size engine, but are completely different to ride.  The Suzuki has a twin cylinder engine with about 65HP, runs smoother and at higher speeds than the KLR and is much better for freeway use than the KLR. 

The KLR is a single cylinder engine with about 35HP and works well for dirt roads and getting away from the pavement.  It works OK on pavement, but not for  big rides of 1000 miles or more, it's just not smooth enough or fast enough for me (it tops out around 75mph loaded for the road).There are bikes and scooters under 50cc.  These are often called pit bikes and have limited use on the street as they do not have the speed to keep up with anything but the slowest traffic.The next range is up to about 500cc.  These are often considered beginner's bikes.   There and many dirt bikes in this range, many of which are full on racing bikes.  It doesn't take a big engine to be a fast and powerful bike.The 600cc bikes are mostly race bikes built for the street, such at Yamaha's R6.600cc to 1000cc.  I would consider these to be basic road bikes, such as Suzuki's SV650, Triumph's Tiger 800, Honda's CB1000.  There are also a class of 1000cc sport bikes like Honda's CRB1000R and the larger dirt bikes like KTM's 990Duke.Over 1000cc lumps together completely different machines such as most Harleys and Victorys, the supersports like Kawasaki's concours, the bigger touring machines like Honda's Goldwing and the adventure tourers like BMW R1200Adventurer.If you like to carve through traffic, a smaller displacement narrow bike like the Kawasaki KLR250 can make a great choice.