Chain or shaft drive?
 

Hi people,
new to the site and absolutely love it!
I'm planning to make a RTW trip or Amsterdam-Cape town within two years from now, depending a bit on budget, time etc.

The big question everyone faces is of course which bike to choose? Lots of info and pro's and con's on weight vs power vs reliability, but no one seems to talk about shaft drive vs chain driven bikes (at least, i can't find it, might just be me).

Here in Holland I drive a bashed up cx500 (due to budget and living in inner city), which is shaft driven and i love it. It has never let me down (nearing 90,000km) and the shaft is totally care free. This experience tilts me towards shaft driven bikes, but the only enduro bikes seem to be BMW's, which are not my type of bike (too expensive and too high tech) for a RTW.

What are the options on shaft driven enduro's? Or can someone convince me chain is just as good/better?

cheers
Paul

Honda?
 

Dont Honda do a shaft drive Trailie? XRV 750?:confused1:

Africa Twin?
 

Thats the Africa Twin right? I believe its a chain driven bike. Beautiful bike. Don't get me wrong, i don't swear by shaft, just have good experiences with it, but am willing to listen to chain enthusiasts!

honda definateley did a shafty v twin.
 

Maybe, but they definateley DID do a shaft drive V twin........

The old Honda XLV750 had shaftdrive:
http://www.xlv750.com/xlv-02m.jpg


As you say there is a lot of Beemers, (airheads are my favorite), but you don’t like them so I guess you have Ural and Guzzi left.

http://www.motorcyclenews.com/upload...zistelvio1.jpg

I know what you mean about shafties, reminds me of my Suzuki GS850G days (1985-1998) (a good reliable and utterly bulletproof Jap tourer). In the case of road based long distance tourers, a well designed and constructed shaftdrive runs circles round a chain driven tourer. As far as Trail/RTW/Adventure bikes are concerned I think a chain drive is much simpler, quicker and cheaper to fix in the event of failure. The other aspect to remember is the increase in weight too, a shaftdrive is much much heavier than a chain and sprocket.

Thats the one I meant!
 

That is just GORGEOUS! I want one...... I Do...really, really, really.... Sod my XT......... ive fallen in love with an inanimate object......:eek3:

Martyn

A RED engine!!!!! I suppose I can see a bit of an attraction though Martyn...

I drove 150.000 km before I changed my shaft. It costed 300€ and no maintenance beside the yearly oil change.
That’s 300€ and 1.56 litre oil in 6 years and 150kkm. If a chain can beat that I guess I have been unlucky with my previous chain-bikes.

..... and it's fun to drive (but not so fun to work on)

spray it?
 

I would'nt care if it was yellow with pink spots mate! its PERFECT! I can always respray it SILVER!

And as for working on it...... I have owned all manner of evil and nefarious bikes in my time....... including a ( dare I admit this publicly?) Mobylette folding scooter! it was cheap on ebay! 11 quid , Yamaha TR1 that i bought in a box ( Engine TOTALLY dismantled by a twonk who couldnt put it back together!) for 50 quid that came with a gasket set, clymer manual ( or was it Haynes??) and a spare set of carbs and a choice of tanks and panels..... Silver or Black...( also Ebay) so a Vtwin Honda scares me not! :mchappy:

Martyn

chain
 

i would say going thu africa i would go for a chain driven if the shaft packs up you wouldn't carry spares for that were as you would carry a spare chain and that would keep you going without much hassel, bike choice i am partial to the yamaha xtz 750 super tenere spares are cheap and readily available on ebay and the bikes go quite cheap as well.
when are you planning to leave, i am planning on going down the east coast of africa in march 2010. london to cape town:thumbup1:

Good point on the weight issue. I have no riding experience outside tarmac europe, where weight is not really an issue. Suppose if you get bogged down in sand/mud you wish your bike is just that couple of kilo's lighter!

Nothing against bmw, just that the stories on the complicated electronics, fuel injection etc scare me off for a RTW trip. Get the impression that the r80/100gs are bullit proof, easy to maintain bikes, wouldn't mind having one of those, expensive though!

When riding through Africa -sand, mud etc- how long does a chain/sprocket set last? Any experience? and can a mechanic in ie Ghana replace it?

Personally I would just find a bike with which you can live for a few months on the road. The chain or shaft is in some respects a re-hash of jap versus old Brit bikes argument. The chain will require more simple maintenance than a shaft, replacement is cheaper and easier also. However which costs less in the long run is a moot point. I like the shaft drive on my BMW ( 1980 R80RT) one day it wil break and cost a lot to fix, but then will run another five years+ with just an annual oil change. It is good not to have to bother with it on my longer trips. BUT. when it does break, it is likely to be a problem, unless it breaks close to home.
in a nutshell, shaft no maintenance until it breaks then is expensive and difficult. Chain, needs regular maintenance with occasional cheap and simple replacements. ( much like brake shoes/pads).

Choices, choices
 

Just take the CX500 Paul!! :thumbup1: (or a nice XJ900 Divy :rolleyes2:). After all, plenty of roads RTW are sealed surfaces, i.e. bitumen surfaced, nowadays.

Actually, those who are shaft drive enthusiasts won't be swayed by anything in a thread and lots of people will swear by a chain drive.
In the meantime, you have not said what kind of riding you want to do, how much weight you expect to carry or even what countries you may ride through - too many variables in other words!

Are you sure there are no threads in here already on this topic? Maybe I have read "so much" elsewhere!

How about a belt drive BTW? :rolleyes2:

Chain drive: Ted Simon's first trip RTW.
Shaft drive: his second trip RTW.
In both cases, he was given the bikes.

The weight issue is funny. As always people think that the traditional BMW-stuff is heavy. I compared the weight of swingarm, beveldrive/sprocket, driveshaft/chain on a R80GS and a F650GS Paris Dakar:

R80GS shaft 12,4kg
F650GS 9kg

That’s not to bad is it? …… Well if you need to carry a spare set of sprockets and chain the weight for the chain-bike will be 12.3 kg! Still 100 gram lighter but you need lubricants, a few chainlocks and maybe some tools.

Conclusion: Shaftdrive is not necessarily heavier then chain and sprockets!

Sidenote:
Small things like chain guard, chain followers and so on are not included in the weight stated above.

So:
Weight – The same
Cost – Shaft is less expensive in the long run
Maintenance – OldBmw has some good points here, personally I would prefer a few hours job every 100-150.000 km then the hassle with a chain.


Who cares?
http://www.actiontouring.com/pic/Kalahari_2.jpg

Since 1977,all of my bikes have been shaft-drive,CX500,6 Goldwings,5 BMWs.

I've done "serious" miles on all of 'em.For instance,my latest bike,bought new on August 1st '07, has done just under 11,000 miles!

I have never had a single problem with any shaft-drive.

Chains belong on bicycles!!

I have to agree with AliBaba, the weight difference isn't big, there is a small weight advantage for chain drive, but not as big as many people think it is.

The main con for shaft is the power loss, which is approximately 18%, chains drives have approximately 11% power loss from the crank. So this clearly dictates shaft drive isn't the best solution for very high performance road racing bikes. But for our consumer use adventure and adventure touring bikes, where 7% power difference wouldn't be noticed, I think we can argue about the cons and pros of each system.

Personally I prefer the shaft-drive. On BMW paralever, you can repair it on the road too, if you know how to do it. You need to carry a main bearing and/or a main seal just in case. They cost less than a good chain set, weight less and take less room carrying them with you.

Very nice armored assault vehicle :), imagine if it was a chain drive and you had to ride home that is 200kms away w/o cleaning and lubricating it, like I often do with my GS - how much chain wear it'll cause? Also if mostly riding on dirt and gravel roads? Even the "sealed" X- or O-ringed chains will give up faster in dirty conditions. Closed systems (both shaft and some enclosed chain drives some older bikes have) are the best there I think in terms of longevity and wear. If riding only on clean tarmac on Western-European and N-American clean main roads then high quality (D.I.D., Regina few other) chains last relatively long (up to 30Kkms, some even more if you aren't a very hard handed rider and clean/lubricate it after every 500km, or after every day when riding in rainy days), but it's a hassle in any case. Your rear wheel will be oily with dirt glued on and your girlfriend (maybe you too if you're too nasty on oiling the chain) will have oily boots, whether you have Scottoiler or you prefer to clean/oil it yourself and you have to keep an eye on it constantly anyway: overall condition, wear of the chain and sprockets, and constantly check&adjust chain slack... In comparision, any 20,000km or more manitenance intervalled (only oil change needed) shaft drive looks very convenient, since you even don't have to touch or look at it in between the maintenance intervals.

In the end of the day each system has it's advantage and disadvantages. Everyone has their own personal requirements, comfort-levels, technical skills and risk assessment in their minds to choose the one that suits the best, IMHO anyways.

Here's mine:

http://i104.photobucket.com/albums/m...S/DSCN8795.jpg

Mine's now at 73Kkm and not a single problem.

Honda did make a V twin with a shaft drive. The St110, and the Deauville as well as the CX500. But depending on what type of travelling you want to do depends on what bike you choose.

As you said most off roaders dont have shaft drive (apart from a few) for weight as most people say and to keep the bike slimmer and other reasons.

As for choosing a bike give us a possible price you would want to spend on (if you dont mind) the bike and we might be able to give you a few bikes we would think about. and what type of terrain you want to go on, road, bit of off roading, hardcore stuff

I plan to go to morroco and i just bought a Yamaha Xt660r for me i find it a great bike, cheap to run, comfy etc but it has a chain when my old bike a deauville had a shaft drive. But there are plenty of things out there to help stop you throwing money at them like scott oilers, degreasers to clean road crap from the chain etc etc

Seem to have spawned quite a discussion here on chains and shafts! After reading through all the posts the only thing one can conclude, as with all these sort of discussions, there are pro's and con's for both systems!

Biking wise I have no experience with long touring outside of europe, but i imagine that if you decide to drive over from up here to SA, it would be fun to get into less familiar type of biking. Probably not the hard core stuff, but some semi offroading, a bit of desert etc seem like a pretty cool experience! So that would probably mean a tenere/africa twin/kle etc enduro style bike. The near daily chain maintenance still scares me off a bit, but if that is what it takes and it can be done without too much problems, it seems like a minor price to pay for a wicked experience!

cheers for al the input

Paul

[QUOTE=Margus;168730]

The main con for shaft is the power loss, which is approximately 18%, chains drives have approximately 11% power loss from the crank. So this clearly dictates shaft drive isn't the best solution for very high performance road racing bikes. But for our consumer use adventure and adventure touring bikes, where 7% power difference wouldn't be noticed, I think we can argue about the cons and pros of each system.
end quote

This is not a fixed thing Margus. On the diesel bike forum where bikes often run with a max of 9hp, transmission loss can be substantial. For instance the old Enfield gearbox when filled with grease as recommended consumes over 25% of the crankshaft power. Switching to 90 grade oil halves this, with a further decrease of power absorbtion when using 50 grade oil. The new (since 1995 or so) 5 speed gearbox on 50 grade oil will often allow a bike to go an extra 10mph, as it absorbs very little power.

Many modern bikes run the gears in the very thin synthetic engine oils which reduce drag to a minimum, wheras the bmw's use separate gear oil of 75/80 weight. Worse for BMW's is that the gearbox is directly coupled to the engine, so there is no primary reduction. This means the input shaft turns 2-3 times faster. to compound this problem, the output shaft is offset to drive the shaft. This forced BMW to use a gearbox that not only spins fast but final drive is via transverse cogs, all of which conspire to drain power. Old Gearboxes and most car gearboxes usually lock the input to the output on the same shaft, so in top gear power is not trasferred by energy wasting gears at all. This normally can easily be checked by looking to see if top gear is shown as a 1:1 ratio. Final drive ratio should always use the least amount of intermediaries for highest efficiency ( and probably component life).

Hmmm...

I did dynoed my GS and guys who've dynoed most of the bikes and have extensive experiences on this field said the BMW-spec gearbox/paralever drive-train is within the power loss spec of most of other modern shaft-drived systems (or my over 60Kkms done GS performed well above factory performance specs to "cheat" the dyno machine results calculation), including japanese bikes with wet clutches and gearboxes floating in the crankcases in a very thin engine oil. I use spec oils only: usually 75W-90 GL5 both in gear- and bevel box.

The pro for BMW engine+gearbox system is all the shafts rotate parallel, which, at least in theory, should give the best mechanical efficiency and longevity - i.e. lot of unusually high mileage BMWs, Honda STs & Goldwings, some Guzzis. Engines where 90-degree turns are done have their own "uneffective" losses. So maybe that's why on dyno the BMW specs the same as other shaft-drived bikes that have all the friction going on in the thin engine oil, but with 90 degree turn at one point before it's transferred into shaft(?) I.e. bikes like Yamaha Diversion, Suzuki GS or VX, Honda XLV etc.

I agree the power loss ratio does vary, that's why I use the word "approximately" anyways. Depends on the temperatures of oils, mechanical details (i.e. Klingelnberg-Polloid spiral pattern in BMW paralevers), ratios, oil viscosity etc. But with modern shaft drived bikes the power loss is around 18% range running in common transmission oils in bevel boxes. I'm sure Enfields etc with different oils (even full of grease variant as you said) have different results and probably have more power loss than the modern siblings.

If you feel that the BMW is lazy because of all the powerloss in the driveline (which I personally don’t think is bad compared to an old beaten up chain) there are plenty of modifications that can be done to increase the power. :devil2:

Somewhere in the North western corner of Tanzania my pannier more or less fell of when I landed after an unplanned jump. Wonder if chain and sprocket would have made it?
http://www.actiontouring.com/jesse/tan2.jpg


BTW. I also have a bike with chain :-)

errr Yes!
 

Wonder why they don't use SHAFT drive on Moto-cross bikes???

They jump a fair way!

Martyn

I guess they don’t have problems with panniers falling off?

MX is a bit different. They spend a few hours with service after they have ridden a few kilometers, but if that suits your travel-style it might be the right choice.

How much do they weigh??
 

Hi Alibaba,
I just cannot imagine what it is about a couple of sprockets and a chain that adds up to 9 Kg.
Can't say I have ever weighed suchlike though.

I would "imagine", again I don't have weighing scales to hand, that the current crop of BMW shafties are heavier than the earlier models - they just look bigger and, therefore, heavier.
So, is it a useful comparison to take an old bike alongside a current production model (including the next generation of F650GS)?. I quite understand that you are riding one, so you have a personal interest!

I do like the way that BMW are prepared to manufacture bikes with all 3 common(ish) drive systems; shaft, chain and belt. In the next few years, we may see more of the chain drive models appearing, or belts for that matter.

Apart from this, I would just like to remind the original questioner that the chain drive bike can have it's gear ratios changed pretty easily - I don't hear or read of shaft drive owners fiddling with their gear ratios.
That's why the "racers" will always have a whole pile of sprockets and gearboxes for the various circuits - lets see how BMW are going to deal with this when they go racing!!

That's because the swingarm are included (for both shaft and chain). The swingarm are very different on shaft vs chain bikes.

Ah!

Maybe difficult to separate out the functions for a shafty, but I may look around for a single-sided swing arm/chain drive and weigh it!
A Duc or a Triumph perhaps??! :rolleyes2:

Just thought of an even more different angle to look at this from, style/looks. I have never has someone say on look at that swing arm of a shalf bike, but you hear it all the time with sometime like a chain drive as they are more flexable and cheaper to produce using less materails to make them.

And there is a bike out there is there not with a seperate swing arm to shaft drive. The yamaha Dragster 800 and the suzuki marauder both have an outter frame for swing arma and a separate shaft drive unit. Looks weird but is more like a 1 off look.

True, although I don't give a vast amount of credence to "styling" - it's important once the engineering is good.

But, there are lots of riders in the showrooms who judge by little else than the looks.

I understand that if thinking on the round the world trip sense or to South africa sense, ok its not a big pro or con, but for some people who use there bike for commuting every day or just for the sunday blast, looks are everything.

Me i like the look of shaftys they are different then most bikes, they stand out instead ohh its a chain again, you can image the gears in there with all the oil, metal and all flying around. I am studying to be an engineer and thing that this is a great idea that bikes have shaft drive. Others just dont like them its down to personall opinions

Take a look at the F800S/ST swinging arm and belt drive in that case!
Best looking swinging arm on the road today, including the Ducs!!
Just a personal opinion of course.

No, the problem with the BMW gearbox is it outputs top gear via gears. so it loses power by sending it across two shafts and through gears. Most gearboxes do not do this. they transfer power direct because the input shaft IS the output shaft. so no gears or layshafts carry power, therefore no power loss at all when in top gear. This is why a typical BMW engine lasts three times longer than a typical BMW gearbox.

input/output shafts on different gearboxes
 

Can you explain how a single 1:1-rotating-shaft-to-engine-speed-on-both-ends can be input and output shaft at the same time in the conventional (not on automatic or semi-automatic or variator type of) gearbox? Only possiblity is if the final drive somehow "switches" between secondary and input shaft (that rotates 1:1 to engine speed) if switching between final gear and all other gears.

My mind says they may be parallel and at the same reflected co-ordinates on both sides of the gearbox (one shaft rotates "over" second), but input and output shaft have to be separated with gears anyway to change gear ratios.


Honda gearbox has a separate input and output shafts:
http://www.offwidth.co.uk/bike/crm_rebuild/gears.jpg



Yamaha gearbox, separate input and output shats:
http://i5.ebayimg.com/07/i/000/bb/6e/302e_1.JPG



Suzuki gearbox, separate input and output shafts.
http://www.mwbbikewreckers.com.au/us...%20Gearbox.JPG



BMW R-series bike gearbox, separate input and output shaft (same as all others):
http://www.bmbikes.co.uk/photos/mech...%20Cutaway.jpg


Or a modern car gearbox:
http://www.f1-blog.co.uk/wp-content/...sg1%5B1%5D.jpg
This illustrates even if the input shaft is the output shaft with separated rotation - the power will go through the gears (they'll not just "stop" to completely isolate any friction) even if it runs 1:1 with crank ratio in the end.


Surfing in the Google I can't find a manual gearbox that nearly 100% transfers 1:1 rotation power (by "stopping" all the secondary shaft(s) rotations) into output shaft w/o touching the secondary shaft(s) that changes the gear ratios...? I may stand corrected here.


The "bulky" gearboxes maybe didn't last long on old airhead BMWs (i.e. like some had bearings failures at around constant 50Kkms etc reports, needed modification to last longer), but on the newer oilheads there are doing some serious mileages on stock gearboxes. I.e. Hank Hits 400,000 Miles on His BMW R1100GS - Lone Star BMW / Triumph Motorcycle Dealership - Austin, Texas,

After 640 000 kilometres and he's still on original gearbox (even pistons and rings aren't changed, no major repairs aren't done on the bike).

Swingarm weight (without shaft and beveldrive):
R80G/S – 2950 gram
R80/100GS – 2140 gram
R1100GS – 3120 gram
R1150GS – 2973 gram
R1200GS – Supposed to be lighter the R1150GS but I don’t have the weight


I’m talking about the “old” 650 GS Paris Dakar and the. Paralever BMW (production ended 1996). Both bikes are out of production but I don’t think that means much for the weight.
Sadly I don’t have the numbers to compare the 1200GS and the new 800GS.

Most shaft driven bikes are powerful with a straight torque-curve. As long as the bike runs “slow enough” (for offroad conditions) there is not much to gain to change the gear ratios. (Eg: My bike runs slower then a KTM 640 ADV in first and faster in fifth gear)

It is possible to change the final drive ratios on the R80/100/R1100GS (don’t know about the 1150 and 1200) and some people do this. But it’s not “common” and it’s more work then changing a sprocket.
Ural has the same option (sidecar rigs have lower gearing), don’t know about the others.

You can also get lower/higher first and top gear for most models.
Remember that most of these bikes also are used by the police and army and they want to drive real slowly.

But again it’s not a common job and with a powerful engine with a straight torque-curve it’s no need – for most people.




BMW has raced for more then 75 years and they still do.
The HP2 wins everything in it’s class. The factory team uses HPN for touring and they use two different gearboxes. As far as I know the “fast” box has only been used in Pikes Peak (and once at Erzberg because the “slow “failed). With the “slow” (standard) box they still have the speed-record at Erzberg (183 km/h).
The racing with HP2 sport might bring more solutions for altering the gearing.

Yes that can be done (I don’t have the numbers), but I don’t see the point. The point must be to compare swingarms on two comparable bikes, one with shaft and one with chain. Maybe a 1200GS and a KTM990…

They do look nice.

I really like the "organic" looks of the new 3-rd generation paralevers with that particular "hole" inside:

http://www.r1200gs.info/misc/images/R1200GS-rearhub.jpg

http://pds.exblog.jp/pds/1/200611/27...9_23145047.jpg


http://www.motorcyclespecs.co.za/Gal...008%20%201.jpg


http://donald.hypermart.net/MCPix/BMW_HP2_SPORT/5.jpg


Most of the single sided shaft drives look aesthetically good.

MotoGuzzi CARC system:
http://blog.crazymoto.net/wp-content...bellagio05.jpg
Looks more "massive", but very nice in its own way.

http://www.motorcyclespecs.co.za/Gal...007%20%203.jpg



Honda:
http://www.f6rider.com/Rune/Rune_large_01.jpg

http://moto.by/articles/image/honda_...rie_rune_3.jpg


Kawasaki system (two sided swing, but still very nice if it's exposed, IMHO):
http://www.rubbermag.com/news/0609/i...3_gtr1400c.jpg


http://www.seastarsuperbikes.co.uk/K...styling_lb.jpg

So there's enough competition from shaft-drives side into chains&belts beauty-contest :)

Good info!

I'm relatively sure the third generation paralever (K1200 and R1200) are lighter looking how light they've got the HP2s.

But it's also strange, while it's the most hevay of them, HPN seems to prefer the 1100 swingarm???

http://micapeak.com/bmw/gs/images/hpnsport.jpg

Or if you have more money to pay them, then you get their own welded version of swing arm:
http://micapeak.com/bmw/gs/images/hpnp.jpg

I think so, but I'm not sure.

The reason why HPN use the 1100 swingarm is that is the longest one. You want the long one to increase wheel-travel.
HPN use the 1100 swingarm as the cheap (haha) solution. They make their own swingarm which has the same length as the one on the 1100.
The HPN swingarm is way more robust then the 1100 swingarm and it gives better room for a wide 18” tire but it is pricey!

If you look on your second photo you will se that it is not an 1100 swingarm, it’s a HPN swingarm.

No I’m not going to remove my HPN-swingarm to weigh it!!! Maybe I will overhaul my gearbox this year and I can weigh it then (the box has never been opened and it’s close to 200kkm)

HPN has the following variations:
-Standard R80/100 swingarm
-1100 swingarm
-1150 swingarm
-Extended monolever
-Standard monolever
-Double sided (?) extended monolever
-Double sided (?) standard monolever

But I guess the 1100 swingarm is the most common solution today.
If you use the 1100/1150/HPN swingarm you can choose between the airhead or oilhead final drives (drum/disk brake)

Note;
The swingarm for the 1200 might be longer, I don’t know.

Hi Paul

I suggest that with a good chainoiler there is no longer a need for shaft drive. I've had fantastic kilometrage out of my chains (Africa Twin) since fitting a Scottoiler.

I think that this allows a much wider choice of bikes for you. Get a chain drive and fit that oiler.

Shaft drive is of course, still an excellent choice, but the oiler opens up possibilities.

Cammys Old Bike......
 

Are you keeping the same theme with your AT then Cammy?

http://i235.photobucket.com/albums/e...uff/biker1.jpg

Never intended to get a discussion going on looks, but there you have it! Thanks for returning back to subject caminando, I had figured the same; either a shaft (limited choice of bikes) or a chain with oiler will do fine for most trips. Cheers for all the input!
Go ahead and have fun talking about looks, gear ratios and the weight of swing arms, i've got the info i need!

Paul

Hey! Don't run away we have more obscure details :rofl:

[quote=pauldelft;169261]Never intended to get a discussion going on looks,
Paul[/quote

But it is all part of the heady equation. So, as Alibaba says, don't stop reading this one!

Good stuff there AliB and Magnus; I do like your pics and the research that you guys have put into your preferred steeds.

me too
 

Oh my god - I'm off to Bike Trader

Hey guys, be kind. some of us still have to use dialup.

Margus

If you look at any old Brit bike, or the new Enfield gearbox you will note that the drive train is arranged like this := The engine output sprocket drives the primary chain to a the clutch hub.
There is usually about a 2:1 reduction here. The clutch hub is free to rotate when the clutch is used, but locked to a shaft when the clutch is closed. This shaft goes from the primary chaincase into the gearbox and is the gearbox input shaft. In the space between the back of the primary chaincase and the input side of teh gearbox sits the gear sprocket which drives the rear chain. The gearbox sproket is mounted on splines on a bearing mounted collar that is free to rotate over the input shaft. The collar extends a little way into the gearbox. There is a gear here that takes power from a layshaft driven gear in all the lower gears. In top gear however, instead of driving via a gear onto the layshaft and back out, the output collar is locked to the input shaft via dogs on a gear which is in the input shaft and splined to it. This locks the output gearbox sprocket to the input shaft. It is possible that some gears may be meshed and rotating, but they are idling and not carrying any power. This is one reason these geaboxes whine (straight cut gears) in all gears except top. It may also account for the higher speeds attained with less power than is needed with some newer designs with offset output shafts. After all, a Tiger cub produced only 10hp so energy conservation was important. Or put it another way, a 650 cc triumph Tr6R with 40hp is about 5 mph faster than a BMW 800cc bike producing 50hp. I am not trying to criticise anyones design, They all were (and still are) compromises based on what the conditions were expected at the time of design and marketing fashion. Nowadays bikes have so much power losing the odd 20hp is of no consequence (except to range/mpg) In the case of the BMW, having a centrally mounted input shaft forced them into having an off set output shaft, in order to clear the rear wheel. When they made the K series.. I expect that the reason for lying the engine on its side was to put the centreline of the engine crankshaft inline with the output shaft, thereby making it easier to construct a longer lived gearbox. But I do not know, never having owned a K series bike, but that is what I would have tried to do.

I've read this 3-4 times, OldBMW, and I need "the picture" despite the bandwidth!
A pic is worth a 1000 words etc.

From the earlier posts:
Considering the single-sided shaft drive, it seemed a good idea to compare its' weight with a single-sided chain drive, such as a Ducati or a Triumph: a Ducati because it is likely to be the lightest example available and a Triumph because they tend to be over-engineered, so it may be at the other end of the scale.
Anyway, thinking about it a bit more, a normal swinging arm on a chain drive bike is possibly lighter overall - don't know basically, and life is too short to go and weigh any!