R vs. K ... Engine comparisons?

[Chrisrides]

Just curious if anyone knows good links to comparions of BMW's R and K engine designs.I forget where, but recently heard someone say or write that the K engine was a better design, but I have no clue. My own intuition would suggest to me that as the R design has been around longer, it should be more developed and understood, but hey .. who knows.

Anyhow, kind of curious to compare engines on several characteristics:
1. cost of maintenance
2. reliability
3. performance

Is there a reason BMW uses the R design in all of it's GS style bikes (ok, I'm a newbie, so don't know if any K's were GS's in the past)

I myself have an R-bike, but am very open to the discussion this thread might open up.

Thx

[Motor31]

Well FWIW the K doesn't require valve adjustments every 6k or less. The K is pretty much light the fire and go.

On mine there has been no need to adjust valves, set timing or synch throttle bodies, ever, in the time I've had it. Change the oil and filter, keep good gas in it and drive it as far as the engine is concerned. Silky smooth the entire time.

Don't equate longevity of the design to indicate superiority on technology otherwise the Harley would be the epitomy of technology.

[st3ryder]

That is an interesting question you ask. One might say, "Take a look at what BMW's bread and butter engine's been for the last 83 years, (R32 was built in 1923, yes?) and decide" which would leave one to believe the R engine's the better, or at least more desirable, since the original "flying brick" is toast, other than on the LT, and the R's gone to its highest level of development with the original architecture more or less intact.

BMW's boxer is its signature engine, much like the v-45/90 and the l-90 easily identify other brands. The R pre-unit engine-gearbox configuration is a much older style that was needlessly imitated in the K compactdrive in 1985, (1984?) in order for the new, water cooled "engine of the future" to look like a "real" BMW, from the flopped layout to achieve horizontal pistons and longitudinal crankshaft, to the triple-shafted gearbox needed to maintain shaft drive.

Some might say that BMW compromised the K's efficiency in order to capture the looks and hertitage of its boxer, and that was the fatal design fault which lead finally to the "correction" of the K engine to the transverse crank, unitised gearbox it could have been from the start, had BMW not tried to appease its "hard core" customers.

That being said, the K's the better engine in a *general* power and maintenance sense. With the advent of the "new" K, there's no comparrison between the power and reliability of the new K with even the most "modern" R, even the R12S, chassis notwithstanding.

One buys an R for different reasons than one buys a K.

[121247]

I have a 05 RT and could not be happier with the bike. It does everything well. I have a summer windscreen which I use in the spring and summer which is great. It makes the bike look very sporty. Putting on a Bos muffler so it will be a little louder with a different look. The RT was the touring bike for 05 & 06 what more can you say.

I think the K1200S is a notable sport bike.

Both bikes are remarkable.
CW
Chicago

[oldpaul]

Originally Posted by Chrisrides

Just curious if anyone knows good links to comparions of BMW's R and K engine designs.
Anyhow, kind of curious to compare engines on several characteristics:
1. cost of maintenance
2. reliability
3. performance

1. Cost of maintenance on my K75 at just over 100,000 miles has been nil in terms of engine. External to the engine, I have had to replace the cooling fan motor for $90.
2. See above
3. K engine produces more power and torque per liter than the airheads.
For example, the K75 makes 101 hp/liter and 67 lbft/liter. The R100GS
produces 61 and 57 respectively.

[PGlaves]

I have a little experience with this topic.

I put 370,000 miles on my K75 - the heads were never off the engine. Transmission never opened up.

Voni has about 315,000 miles on her R1100RS. (She had 172,000 on her RSL which she sold recently.)

The Boxer had a valve job at 295,000 miles. Original rings and botom end still in place. It did have a fluke breakage of a valve chain guide - $7 plastic part requiring engine teardown to bare cases to replace.

Boxer - more seepage eventually, head gaskets, cam sprocket access plugs, etc. Throttle bodies tend to experience shaft wear after a while.

The truth is that with regular routine maintenance they are both solid platforms. The K is easier to keep in top tune however. Compared to most other motorcycles available out there, either is a good durability choice from an engine standpoint.

[Chrisrides]

I appreciate the repsonses here. It would be interesting to see if BMW would come up with a K-GS configuration, but even as I'm typing this I am wondering if the reason this has not been done is due to the liquid-cooled aspect of this engine (ie. fewer systems, as in liquid cooling, may be better in possible harsher environments). Don't get me wrong, I very much like both streams BMW is developing, and it will be equally interesting to see how the parallel twins do. I had an aprilia before and really like the rotax engine.

[PGlaves]

Originally Posted by Chrisrides

I appreciate the repsonses here. It would be interesting to see if BMW would come up with a K-GS configuration, but even as I'm typing this I am wondering if the reason this has not been done is due to the liquid-cooled aspect of this engine (ie. fewer systems, as in liquid cooling, may be better in possible harsher environments). Don't get me wrong, I very much like both streams BMW is developing, and it will be equally interesting to see how the parallel twins do. I had an aprilia before and really like the rotax engine.

I don't see liquid cooling as an obstacle at all. After all, they did do the F650 GS, GS Dakar, and real Dakar Rally bikes with liquid cooling.

[hcmiller52]

I went through the same mental juggling you are. I have a new '06 1150GS Adv which replaced my '96 R110RT. I had a Vulcan cruiser, too, which I couldn't stand riding anymore (BMWs will to that to a fella) so I wanted to trade it for another (used, though) BMW. I did a little reading and wound up buying a '98 K1200RS, without so much as even starting up the engine (the bike was and is still like new, even with 49,000 miles) and when I rode off the lot the forst time, it was love in the first 100 yards. Even after the honeymoon period, we're still in love. Smooth and extremely fast compared to the GS. That said, it is a different bike - and a different love - I love the GS and the boxer engine, too. Hands down, though, the brick engine is cheaper to maintain so it runs well. The boxer is an out...uh, older design and, while relatively *simple* to maintain, it reminds me of the Volvos I used to own which always seemed to need a valve adjustment, even soon after you just did a valve adjustment. The four doesn't need this coddling and does 0-60 in 3.6 to boot.

[knary]

Folks seem to be talking about the old K, not the new K as found in the K1200S. It seems nearly as different from the old flat K as the old K is to the oilhead. Sure, both K's are in-line designs, but that's about it, no?

[PGlaves]

I cursed BMW severely the day I found out they named the new upright-sorta transverse 4 cylinder bikes "K". Like there aren't enough other letters in the alphabet.

And yes it is confusing - and they apparently know it now: Notice that the new "K1200R Sport" wasn't named K1200RS even though that is what it is - but would be confused with the other K1200RS.

At least they picked a different letter "G" for the new line of 650s.

Back when they named the Oilhead bikes "R" they did it for cultural and heritage reasons dating back to 1923. The saving grace was that the smallest Oilhead motor in general production (not counting the Dakar Rally bikes) was 1100cc and the largest Airhead in general production was 1000cc so we could tell the difference between an R1100 and an R100 - even when people screw up on Ebay and call their R100 an R1000.

[PGlaves]

Originally Posted by knary

Folks seem to be talking about the old K, not the new K as found in the K1200S. It seems nearly as different from the old flat K as the old K is to the oilhead. Sure, both K's are in-line designs, but that's about it, no?

There is virtually nothing the same about the two K motors.

To the original question, I don't think anybody has much of an answer relative to the new K models. Not enough folks have enough miles on that motor to know very much. Once there are many bikes with 100,000 plus miles on them we might be able to draw some conclusions. Early failures are usually flukes. Case in point - Voni's R1100RS broke a cam chain guide rail - $7 part requiring engine removal and teardown to replace. I told BMWNA at the time that I thought it was embrittlement and that they had a ticking time bomb on their hands. I was wrong. I've heard of a few other cases but not the incidence I expected to happen. I've concluded it was a fluke!

[Motor31]

Originally Posted by PGlaves

I cursed BMW severely the day I found out they named the new upright-sorta transverse 4 cylinder bikes "K". Like there aren't enough other letters in the alphabet.

And yes it is confusing - and they apparently know it now: Notice that the new "K1200R Sport" wasn't named K1200RS even though that is what it is - but would be confused with the other K1200RS.

At least they picked a different letter "G" for the new line of 650s.

Back when they named the Oilhead bikes "R" they did it for cultural and heritage reasons dating back to 1923. The saving grace was that the smallest Oilhead motor in general production (not counting the Dakar Rally bikes) was 1100cc and the largest Airhead in general production was 1000cc so we could tell the difference between an R1100 and an R100 - even when people screw up on Ebay and call their R100 an R1000.

+1. I think it's ok to reuse the same designation from a discontinued line (ie) the airhead to oil heads. There really isn't any confusion there as the engine sizes changed sine the airheads topped out at 1000.

In the case of the K bikes, as long as there are 2 styles of inline water cooled engines being sold simultaneously they should have seperate identities.