Well with EFI, 450 cc can a decent amount of power in a light bike. I its original guise, the BMW 450 produced closer to 52 hp, but was a racing engine, with titanium valves and very short service intervals. I believe CCM have detuned it to 40 hp (about the same as a Tenere which I think is 43?) but the bike is a good 50-60kgs lighter than a Tenere.

I think the weight of 650cc engines and bikes is an issue manufacturers havent bothered to address ... as they dont see it as important. Which is unfortunate for people who do see it as important.

I weighed my 650cc Rotax donk a few years back and it was right on 50 kgs. Looking at the Yamaha equivalent, which looks a lot heavier and bulkier, I wouldnt be surprised if it was 60 kgs - which is the weight of a KTM 990 V-Twin engine. KTM have got its 690 engine down to about 39 kgs. Which makes me think if Rotax or Yamaha actually put some effort into making their 650 cc singles lighter, they too could bring them down to the 40 kg mark.

The latest KTM singles up to 500 cc are down to around 29 kgs. I am guessing my 60 hp Husaberg 570 engine is somewhere around 32 kgs. And I would think the BMW 450 engine is also around 30-32 kgs.

While Yamaha will spend a lot of time, effort and money making their 450cc engines as light as they can while maintaining durability, there seems to be zero interest on their behalf to make their 650 cc engine lighter (there's got to be 20 kgs they could trim off it with little effect on durability) or to make the actual bike lighter (probably another 20 kgs they could trim off there). For some reason, manufacturers see 650 cc bikes as single cylinder tanks with no motivation to optimise weight. Whereas the 450cc equivalents offer lean, weight optimised engines and bikes.

A look at whats possible in weight reduction can be seen in the swedish engineered Highland 950cc V-twin (before the tragic plane crash)... 130 hp from just 44 kg engine ... now in a streetbike that weighs just 144 kgs. http://www.motorcyclistonline.com/fi...g/viewall.html

The 50 kg 650cc rotax in my XC is over 20 years old in design. The only changes in that time have been to the head. Fine tune cams, combustion chamber, fuel injection etc. They never even got around to adding a 6th gear. A bit of focussed redesign work could cut 10-12 kgs off the engine and gearbox and add an additional gear.

No-one has bothered with it, cause 650cc engines just dont need to be sexy apparently. Market research seems to tell them that 650 buyers arent picky. KTM at least has put come effort into its current 650 - 690cc engine ... probably because the engine is also used in its sporty duke. Problem is the engine has the Dukes narrow, street racer gearbox.

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