R1150R VS K1200R Spec questions Expert help needed

[hep303]

I need to know some things. A friend of mine wrecked his R1150R and bought a new K1200R. It is massively more powerful than the R. What is it that gives the K so much more horsepower and torque with only about 50cc more displacement?
My limited knowledge of engine design prohibits my understanding. I have heard about bore and stroke, but I don't know much about it. If a similar size engine puts out about double the power, what is lost? The K gets about 35+ MPG so gas mileage is not really sacrificed. Does it have a much shorter lifespan than the boxer engine? Does the 4 cyl K engine produce 80 extra horses by magic?

[dwayne]

I need to know some things. A friend of mine wrecked his R1150R and bought a new K1200R. It is massively more powerful than the R. What is it that gives the K so much more horsepower and torque with only about 50cc more displacement?
My limited knowledge of engine design prohibits my understanding. I have heard about bore and stroke, but I don't know much about it. If a similar size engine puts out about double the power, what is lost? The K gets about 35+ MPG so gas mileage is not really sacrificed. Does it have a much shorter lifespan than the boxer engine? Does the 4 cyl K engine produce 80 extra horses by magic?

Odd, I too wrecked my R1150R and am replacing it with a K12R.
Although the answer would seem obvious to this question...it isn't. True the K bike has 2 more cylinders, but again the total of the those two extra cylinders is another 50 cc over R1150R. Is this a compression thing? I know NOTHING of motors. Obviously.

[iowabeakster]

oops screwed up the post, see next one.

[iowabeakster]

No expert here, but I can maybe get you started.


The more cylinders you have, the more "pushes" (ignitions) per RPM.

i.e. (for four-stroke engines)
1 cylinder engine has 1 "push" per 2 crank shaft revolutions
2 cylinder engine has 1 "push" per 1 crank shaft revolution
4 cylinder engine has 2 "pushes" per 1 crank shaft revolution
6 cylinder engine has 3 pushes per spin
etc.


The more frequent the "pushes", the engine operates more efficiently. Part of this has to do with the deceleration of the engine parts between the "pushes". Less frequent pushes means more deceleration in between. Therefore with more cylinders the power is more "continuous". This is a significant improvement in efficiency.

Another factor is when you divide up an engine into smaller cylinders, the pistons, rods, bearings, and crank can be lighter. The force created by these smaller cylinder's "push" is less, and lighter materials, bearings can be used.

Of course producing a "multi" cylinder engine means extra cylinders, pistons, valves, bearings, etc etc etc...makes a more expensive engine to manufacture.

If you have an engine that has a SMALL BORE, LONG STROKE you will have an engine that produces more low RPM torque. (think farm tractor)

If you have an engine that has a BIG BORE, SHORT STROKE you will have an engine that produces for high RPM horsepower. (think formula 1 race car)



I was very surprised when I finally noticed the dimensions on our "twin" R1150R.
I was expecting more "grunty" dimensions. The Big Bore, Short Stroke motor definitely likes to spin spin spin.

[ProductUser]

The water-cooled nature of K-bikes also helps produce more power. Let's not forget about the valve train (e.g., intake and exhaust valve sizes, lift and duration), which is different than our R bikes. Oh, what about the compression ratio between the two? What about the shape of the combustion chamber and the shape of the pistons (e.g., domed pistons)? There's also the engine management system to also consider.

There are a lot of differences that can account for the extra hp/torque between the two bikes. I don't have all of the answers, but I just listed a few for illustration purposes.


ProductUser

[CycleRob]

The main reason is something nobody mentioned. Total piston area.

Figure out for a 650cc engine where bore=stroke in 1,2,3,4 and 6 cylinders and you'll see huge differences. I can do the math, but am not in the mood for it now.

650=(pi) d squared/4 * (number of cyl) . . . . . . (solve for d with different number of cyl)
Piston area=(pi) * (d//2) squared * (# of cyl)

Also as the pistons get smaller with more cylinders, the RPM's go up dramatically. A 1 cyl 650 may rev to 7,000, whereas a 6 cylinder 650 can go to 18,000. As it is reving much higher, it's larger piston area is "pushing" on the crankshaft rod journals more often, making them rotate.
Larger pushing area, more frequent pushes and also a higher volumetric efficiency of filling and emptying many small chambers compared to 1 large one.

The advantage of less cylinders is cooler running, higher fuel economy and the economics of less parts to manufacture and assemble. You would want a 6KW generator to be a 1 cylinder for longer fuel runtime. Motorcycles choose the # of cyl based on what is wanted: simplicity, light weight, fuel economy, performance, low vibration, wide powerband, high peak HP, etc

You know where our air cooled OilHeads fit in with their 2 cylinders.
It was intentional.

[hirsty]

Good Q&A here, interesting to read.

You can see a lot of this debate in racing at the moment, with Ducati (twin) wanting a rule change increasing capacity limits to run their new bike against the Japanese fours.

[hass]

I have owned a K1200S and the power is indeed addictive and exciting. However, all that power means the bike requires much more focus when riding - which is a pain when in town traffic.

I swapped to the R1200R because although it has less power - this power is delivered much more smoothly. Plus it has enough power for all my needs - the only difference being I have to open the thorottle to 80% instead of 25%. Another big factor was the handling. The R12R handles way better than the K12S - it is much more flickable. This is why Motorrad crowned the R12R king of the alps and not the K12R. I recommend all owners of R1150Rs to test the R12R before they go out and buy a K-bike.

[geothepencil]

Consider also that the twin cyl R1200S in its higher state of tune compared to an older R1150R can be a worthy opponent to a K1200R or other 4 cyl sportbikes in the actual business of riding. They have done very well in Europe and here as well in the Moto-St series this year. And they are running stock motors for the most part.

geo