Displacement...
Since it's sort of on my mind at the moment, I thought I might also take a moment to tease out my thoughts on the matter of engine displacement being only one factor of many that plays part in the overall suitability of a motorcycle to a given set of tasks. Blanket statements of "you need X amount of displacement for task A" or a "rider with less than P amount of experience shouldn't be on a bike with more than Y" displacement are troublesome because they really don't take into consideration all of the factors that go into any one single model of motorcycle.
Now, generally speaking I rarely recommend that new riders start out on anything that's much more than 600cc though sometimes I will recommend a bike that displaces 900cc. And even within that "not much more than 600cc" range I'll discourage new riders from even looking at certain bikes. Why this seemingly maddeningly strange maze? Well, it gets back to questions of purpose, design and implementation...and that different engines perform differently.
Wow...what an oddly obvious statement to make but one that seems to get left pinned to the corkboard at home when these kinds of discussions fire up. Let me state this clearly, an increase in engine performance in terms of power output and delivery do not necessarily track linearly with larger displacements for every type/configuration of engine. Yes, you usually get more, but more of what and where you get it are the key factor, not that bike simply has bigger cans.
So...this is what I mean...
From the factory my 1999 SV650S produced 71HP@9000 RPM (46 ft/lb of torque at 7400) with a perfectly balanced 90 degree water cooled v-twin displacing 645ccs. With an after market exhaust and re-jet it was pushing slightly more than 80HP. (and 50ft/lb of torque) A stock 2010 Triumph Scrambler, displacing nearly 850cc puts down just 50HP@6800 RPM but throws down 50ft/lb@4,750. So it's a bike with more displacement but lower horsepower and about the same amount of torque...but that torque is delivered lower in the revs where it can be fairly easily put to use by novice riders. The lopey, easy-going not-quite-rev-happy nature of the Scrambler's mill is a further recommendation for it as a starter bike even though, by displacement, it clearly falls out side of the range that conventional wisdom suggests should be a good starter bike. There are, of course, other factors too; the Triumph is fairly low, very comfortable, approachably non-intimidating, confidence inspiring, and relatively light.
Similarly, a bike like...say...a Honda CBR600RR is a very poor choice for a first bike, in my opinion, even though it is considerably lighter than either the SV650 or Scrambler. See...It's mill only pumps out 96HP and 42ft/lb of torque, but it does so at a screaming 13,600 and 11,300 RPMs, respectively. While the torque and horsepower numbers seem better for novice riders they're so far up in the revs that it's actually hard to make good use of them while learning to become at least a smooth, proficient if not actually a confident rider. Pile on-top of that a very committed riding position with sharp handling bestowed upon this beast by Honda as a Sell On Monday repli-racer and...It's just not a winner for the newly minted rider.
Of course this really isn't a discussion of what the best bike for a beginner is, it's just an example to help illustrate the point that fixation on displacement doesn't give a full picture of performance.
To further illustrate my point, engine tuning has a fairly significant role to play as well. When I went from the SV650S to the Aprilia SL1000R Falco I honestly didn't feel that it was that big a change in terms of performance despite a difference of 352ccs displacement between the two. As delivered from the factory the Falco put out 86HP and 60ft/lb of torque and did so at 8750 and 7000 RPM, so not too dissimilar from the SV. Most of the 'overage' was eaten up by the extra weight the Falco carried over the SV; performance wise, by power and weight, they were very similar in spite of the difference in displacement.
Were? Oh yeah, that whole tuning thing I was mentioning. So, the Falco, was dramatically restricted and kind of over weight. Popping the restrictor plate out of the airbox and cutting a ground wire to the ECU (which engaged the unrestricted map) quite literally dumped 31 more horses into the corral yet curiously torque didn't change all that much from 60ft/lb (it's between 60 and 65, now) yet something special did happen; the power band suddenly became nice and fat, coming on strong at 6000RPM and pulling like a freight train to red line at 10.5K RPMs. Dumping the stock exhaust for a set of Two Brother's cans fattened the power band further by a touch and dropped 20lbs of pork further enhancing the gains from de-restriction. Without the ability to get more air into the engine a 1 liter v-twin may only be marginally more performant than a 650cc v-twin.
So yes, in principal larger displacement does mean that an engine has the potential to move more air and fuel through it thus generating more power, but where that power manifests itself (in revs or in torque) is complex matter of overall design. ( Crazy things like bore and stroke, valve sizing and lift duration/overlap, timing advance, intake volume and runner length, exhaust throughput and back pressure...) Simply stating that bigger is better doesn't capture all of these factors nor does it take into consideration intended task. (In other words, what the damn thing's going to be used for!) An engine that has boat-loads of torque down low may not have very long legs and an engine that has a crap-load of HP might have not much usable torque without revving the snot out of it; both have their pros and cons which I won't go into.
All of this has been churning in my head since a friend had mentioned that, after pimping around a newer model GSXR-1000 (which is a completely absurd motorcycle for street use at 191HP and 87ft/lb), that anybody who claims 600ccs isn't enough for the streets simply doesn't really know how to ride a 600. I tend to agree with this sentiment but I think it can be refined a little: Regardless of displacement, a rider who is familiar and comfortable with their bike's power delivery will always be able to get more performance out their motorcycle than a rider who isn't.
Now, generally speaking I rarely recommend that new riders start out on anything that's much more than 600cc though sometimes I will recommend a bike that displaces 900cc. And even within that "not much more than 600cc" range I'll discourage new riders from even looking at certain bikes. Why this seemingly maddeningly strange maze? Well, it gets back to questions of purpose, design and implementation...and that different engines perform differently.
Wow...what an oddly obvious statement to make but one that seems to get left pinned to the corkboard at home when these kinds of discussions fire up. Let me state this clearly, an increase in engine performance in terms of power output and delivery do not necessarily track linearly with larger displacements for every type/configuration of engine. Yes, you usually get more, but more of what and where you get it are the key factor, not that bike simply has bigger cans.
So...this is what I mean...
From the factory my 1999 SV650S produced 71HP@9000 RPM (46 ft/lb of torque at 7400) with a perfectly balanced 90 degree water cooled v-twin displacing 645ccs. With an after market exhaust and re-jet it was pushing slightly more than 80HP. (and 50ft/lb of torque) A stock 2010 Triumph Scrambler, displacing nearly 850cc puts down just 50HP@6800 RPM but throws down 50ft/lb@4,750. So it's a bike with more displacement but lower horsepower and about the same amount of torque...but that torque is delivered lower in the revs where it can be fairly easily put to use by novice riders. The lopey, easy-going not-quite-rev-happy nature of the Scrambler's mill is a further recommendation for it as a starter bike even though, by displacement, it clearly falls out side of the range that conventional wisdom suggests should be a good starter bike. There are, of course, other factors too; the Triumph is fairly low, very comfortable, approachably non-intimidating, confidence inspiring, and relatively light.
Similarly, a bike like...say...a Honda CBR600RR is a very poor choice for a first bike, in my opinion, even though it is considerably lighter than either the SV650 or Scrambler. See...It's mill only pumps out 96HP and 42ft/lb of torque, but it does so at a screaming 13,600 and 11,300 RPMs, respectively. While the torque and horsepower numbers seem better for novice riders they're so far up in the revs that it's actually hard to make good use of them while learning to become at least a smooth, proficient if not actually a confident rider. Pile on-top of that a very committed riding position with sharp handling bestowed upon this beast by Honda as a Sell On Monday repli-racer and...It's just not a winner for the newly minted rider.
Of course this really isn't a discussion of what the best bike for a beginner is, it's just an example to help illustrate the point that fixation on displacement doesn't give a full picture of performance.
To further illustrate my point, engine tuning has a fairly significant role to play as well. When I went from the SV650S to the Aprilia SL1000R Falco I honestly didn't feel that it was that big a change in terms of performance despite a difference of 352ccs displacement between the two. As delivered from the factory the Falco put out 86HP and 60ft/lb of torque and did so at 8750 and 7000 RPM, so not too dissimilar from the SV. Most of the 'overage' was eaten up by the extra weight the Falco carried over the SV; performance wise, by power and weight, they were very similar in spite of the difference in displacement.
Were? Oh yeah, that whole tuning thing I was mentioning. So, the Falco, was dramatically restricted and kind of over weight. Popping the restrictor plate out of the airbox and cutting a ground wire to the ECU (which engaged the unrestricted map) quite literally dumped 31 more horses into the corral yet curiously torque didn't change all that much from 60ft/lb (it's between 60 and 65, now) yet something special did happen; the power band suddenly became nice and fat, coming on strong at 6000RPM and pulling like a freight train to red line at 10.5K RPMs. Dumping the stock exhaust for a set of Two Brother's cans fattened the power band further by a touch and dropped 20lbs of pork further enhancing the gains from de-restriction. Without the ability to get more air into the engine a 1 liter v-twin may only be marginally more performant than a 650cc v-twin.
So yes, in principal larger displacement does mean that an engine has the potential to move more air and fuel through it thus generating more power, but where that power manifests itself (in revs or in torque) is complex matter of overall design. ( Crazy things like bore and stroke, valve sizing and lift duration/overlap, timing advance, intake volume and runner length, exhaust throughput and back pressure...) Simply stating that bigger is better doesn't capture all of these factors nor does it take into consideration intended task. (In other words, what the damn thing's going to be used for!) An engine that has boat-loads of torque down low may not have very long legs and an engine that has a crap-load of HP might have not much usable torque without revving the snot out of it; both have their pros and cons which I won't go into.
All of this has been churning in my head since a friend had mentioned that, after pimping around a newer model GSXR-1000 (which is a completely absurd motorcycle for street use at 191HP and 87ft/lb), that anybody who claims 600ccs isn't enough for the streets simply doesn't really know how to ride a 600. I tend to agree with this sentiment but I think it can be refined a little: Regardless of displacement, a rider who is familiar and comfortable with their bike's power delivery will always be able to get more performance out their motorcycle than a rider who isn't.