Author Topic: Starting the research on R80 and K75  (Read 1258 times)

Offline Adam M

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Starting the research on R80 and K75
« on: July 11, 2018, 08:14:43 PM »
After a month spent in Europe on slightly modified R80 I decided to research it together with K75.
My Triumph T150V rides great, unfortunately my body feels quite beaten up after a ride longer than 100 km.
I know I could improved it further by installing better front end with better brakes, better rear shocks, but don't want to mess with original bike.
So probably has to sell it in a year or two and go a BMW route.
Only problem I see with BMW, I'm short ( 173 cm tall ) so my first question is how high K75 is ?
I was OK with R80, but it's seat was lowered.
Another question, could somebody compare both bikes ?

Thank you.
Ah, I'm from Mississauga, Ontario.
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  • Triumph T 150 Trident.

Offline Laitch

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Re: Starting the research on R80 and K75
« Reply #1 on: July 11, 2018, 08:39:51 PM »
I'm short ( 173 cm tall ) so my first question is how high K75 is ?
K75 models came in a standard seat version or a low seat version. The low seat is 760mm high. It has a profile and seat components distinct from the standard seat. The red bike is a low seat version. The arrows show its unique tank pad and how the seat has a sloping profile. The low seat is not hinged; it can be slid off to access the battery.


The black bike has a standard seat. The seat is 810mm high. The arrows show its horizontal profile and its battery cover which is not present on the low seat model. The standard seat is hinged for access to a small tool box and the battery beneath the tool box.
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Martin

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Re: Starting the research on R80 and K75
« Reply #2 on: July 11, 2018, 09:05:21 PM »
 Go here to compare http://cycle-ergo.com/. You can also have the seat nose shaved or the whole seat lowered by a competent upholsterer experienced with motorcycle seats. You can buy motorcycle boots with the thickest soles available, they can vary in thickness by up to 1. You can add lifts to the boots, if doing both buy the lifts first to try in the boots as some boots wont accept lifts. Doing both will increase your height by 2"+.You can drop the forks through the trees by 1/2" without noticeable effects on the handling. There is a shorter rear shock available but it can effect clearance and it will be harder to get onto the centre stand. The stand can be shortened to suit. I am 1" shorter than you and with a Jo foamed lowered seat and thick soled motorcycle boots I can flat foot with slightly bent knees.

Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Chaos

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Re: Starting the research on R80 and K75
« Reply #3 on: July 11, 2018, 11:42:56 PM »
Hard to compare an r80 and a k75.  The r has more character but is more fiddly with carbs and valve adjustments.  The k is smoother and feels more top heavy.  Both are great bikes, I could live with either. 
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

Offline Martin

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Re: Starting the research on R80 and K75
« Reply #4 on: July 12, 2018, 01:53:43 AM »
When I first started looking for a bike, a couple of mates with Hardleys tried to talk me into one. :hehehe I looked at Guzzi's before looking at BM's. I used to have a work colleague that had a R90s that I drooled over. So after talking to a guy I worked with who was an Ex BM Hardley tech his advice was to go for a BM. I was looking at R80's he told me to have a look at K75's. I still love the look of the R80 especially with a bikini fairing.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline blackie1

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Re: Starting the research on R80 and K75
« Reply #5 on: July 12, 2018, 03:37:34 AM »
hi Adam m
i have owned both and if forced to choose then my personal preference would be the k75 all day long.
smoother, accelerates quicker and more nimble than the R80
the R80's sheer simplicity  and ease of accessibility however beats the K75 which is a bit more complex with the fuel injection.
flip a coin
everyone's a winner baby
 :2thumbup:
  • new zealand , where else would u want to live, really
  • 1991 K75RT naked 40,000kms

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #6 on: July 12, 2018, 08:56:19 AM »
K75 is also much cheaper in my area, but not many of them show up.
After 15 years with old british bikes, carbs are not fiddly to me at all :), however K's fuel injection would be a think to master.
From what I read on the forum engine is pretty much unburstable, gearbox, shaft and final drive are R80 parts anyway.
I thought about K because I like triples, and liquid cooling makes engine temperature more stable.
With Triumph during a hot day I start with cold engine and very slow idle to have a racing engine on idle after some traffic jams in town.
But inevitably the cooling and FI makes it much more complicated comparing to R80, which is as reliable, simple enough for me to do not only maintenance but all the possible repairs by myself and is not affected by heat at all. A month ago I was riding through Berlin in 30C degrees days without any problems.
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Offline Chaos

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Re: Starting the research on R80 and K75
« Reply #7 on: July 12, 2018, 09:07:57 AM »
r80/r100 beats the K75 as far as simplicity, but in 200k I have never touched the FI on mine except to replace aging fuel lines.  And I've only checked the valves about 4 times, changed shims on 3 or 4 of them.  Biggest issue might be price, R's seem closer to having a collector's mystique than K's. 
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #8 on: July 12, 2018, 10:10:52 AM »
Perhaps you should clean injectors ? :).
On the different note is your Dnepr side valve ?
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Offline Chaos

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Re: Starting the research on R80 and K75
« Reply #9 on: July 12, 2018, 11:17:19 AM »
Perhaps you should clean injectors ? :).
On the different note is your Dnepr side valve ?
Haha, Techron seems to do the trick.  And no, it's a Ural with overhead valves, similar to a /2 with the pushrod tubes above the cylinders. 
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #10 on: July 12, 2018, 11:33:20 AM »
Aha, I had a close encounter with such a machine 10 years ago, helped a friend to cure a hole in one piston and installed electronic ignition in it.
It changed a bike a bit with much easier starting and even idle. However his was an older Ukrainian home market model.
I also believe you use an old picture of my polish virtual friend working on her K750 :).
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Offline Gibson

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Re: Starting the research on R80 and K75
« Reply #11 on: July 12, 2018, 11:34:10 AM »
I have a r100r Mystic and a K75 both 94 models. I also rode a 92 r100r for about 25k miles. I've been riding the K75 every day now. The R100 is much lighter maybe by 100 lbs. My R100M is a smaller bike. The seat is lower it handles better and has much better front brake setup and better rear suspension than the K. The K bike shifts better, starts easier, is smoother, has clock and gear position indicator, no charging issues, no fuel petcocks, no overheating in traffic etc. It appears that BMW attempted (and very successfully so) to solve some of the shortcomings with the Rs. I love the R bikes for its simplicity and charm. I don't think you can go wrong with either.
  • Dix Hills NY
  • K75 ABS and R100Mystic

Offline Laitch

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Re: Starting the research on R80 and K75
« Reply #12 on: July 12, 2018, 11:53:16 AM »
. . .  it's a Ural with overhead valves, similar to a /2 with the pushrod tubes above the cylinders.
Doesn't it also have an oil filter instead of an oil slinger—as a nod to evolution? :giggles
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Chaos

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Re: Starting the research on R80 and K75
« Reply #13 on: July 12, 2018, 12:24:26 PM »
actually it has both, very low pressure pump (3-5 psi) with filter and a slinger for what doesn't get splashed or dripped on.  And yes, I stole that avatar because she is just too damn gorgeous!
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #14 on: July 12, 2018, 04:43:02 PM »
How can I edit posts ?
I made a mess in another thread, trying to insert a picture from postimage.org and don't see any edit button around a post body ?
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Offline Laitch

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Re: Starting the research on R80 and K75
« Reply #15 on: July 12, 2018, 05:18:13 PM »
How can I edit posts ?
I made a mess in another thread, trying to insert a picture from postimage.org and don't see any edit button around a post body ?
There are a couple of images of a bike in one of your threads. We don't get modify buttons right off the bat so you should carefully Preview your posts until you get one. We'll all just live with your messes until you have means to clean them up. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Laitch

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Re: Starting the research on R80 and K75
« Reply #16 on: July 12, 2018, 06:01:30 PM »
. . . however K's fuel injection would be a think to master.
The thing about the L-Jetronic system on a K75 is that there is nothing to master so you don't need to think about it; however, if you buy a clapped-out, neglected, used K-bike what you'll need to master is electronic diagnosis using a multi-meter so you can go through all the Jetronic functions to determine if the ohms and voltage are at spec, only to find out that what you should have done is replaced the fuel filter and fuel hoses. :giggles
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Gibson

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Re: Starting the research on R80 and K75
« Reply #17 on: July 12, 2018, 06:09:08 PM »
Fuel injection on these bikes is very basic by today's standards, but it works very well. These bikes are as easy to work on as the R but a bit more technical. I have been riding R bikes for 40 years but enjoy working on the K
  • Dix Hills NY
  • K75 ABS and R100Mystic

Offline stokester

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Re: Starting the research on R80 and K75
« Reply #18 on: July 12, 2018, 06:41:18 PM »
Fuel injection on these bikes is very basic by today's standards, but it works very well. These bikes are as easy to work on as the R but a bit more technical. I have been riding R bikes for 40 years but enjoy working on the K
Same here, I've been able to do all the diagnosis, work, and certainly all the maintenance so far on both types of BMWs following advice found here and other online forums.  The extra complication of fuel injection is a non-issue to me with only the fuel pump, filter, lines and injectors added to the mix.  I'm sure it has failed on some but the control module appears to be pretty robust.  After all I'm sure all of us depend on these systems in our daily drivers.

The most complex thing I diagnosed was the ABS and using on-line references and analog meter I was able to get the brain fixed by Tosi in Japan.
  • Yorktown, Virginia
  • 94 K75S - 93 K75S - 91 R100RT - 78 R100S

Offline Gibson

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Re: Starting the research on R80 and K75
« Reply #19 on: July 13, 2018, 07:16:21 AM »
I think the K75 makes an ideal daily commuting machine. So care free and easy. It appears convenience was important in this design. If it was only a bit lighter...but then it wouldn't ride like it does I guess. I ride the K every day to work and love it. I feel like I've been missing out on some very cool machines this whole time. :riding:
  • Dix Hills NY
  • K75 ABS and R100Mystic

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #20 on: July 13, 2018, 07:39:34 AM »
What's the weight of K ?
How easy / hard is to place it on a center stand ?
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Offline Laitch

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Re: Starting the research on R80 and K75
« Reply #21 on: July 13, 2018, 09:30:02 AM »
What's the weight of K ?
How easy / hard is to place it on a center stand ?
The weight of a naked K75 is approximately 500lbs. Go to the following site for all points of comparison among most BMW motorcycles. http://www.bmbikes.co.uk/bmwmodels.htm

It will be difficult for you to place it on the side stand if you have poor abdominal core strength and weak leg muscles.
  • Along the Ridley in Vermont.
  • 1995 K75T 68,000 miles
I wept because I had no radials until I met a man who had no splines.

Offline Gibson

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Re: Starting the research on R80 and K75
« Reply #22 on: July 13, 2018, 09:46:38 AM »
If you use the right technique it is about the same as my R100 (not bad at all). The K has a conveniently located grab handle that folds out above the left foot rest. If you use that, and focus on stomping down as you lift it, its not bad at all. I always center stand both bikes. Very important on R bikes, not sure yet with k.   
  • Dix Hills NY
  • K75 ABS and R100Mystic

Offline Adam M

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Re: Starting the research on R80 and K75
« Reply #23 on: July 13, 2018, 10:38:24 PM »
I'm dangerously close to 70, but still squat with some 100 something lbs on my back and dead lift the same.
So leg muscle and core are still there. :)
Also can still put my Trident on the center stand, what could give a hernia to a young man. It's weight is 500 lbs too, but stand is bloody difficult.
Laitch, thanks for another great source, Gibson - K bikes have to be center stand too. Left on the prop stand they tend to smoke.
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Offline Chaos

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Re: Starting the research on R80 and K75
« Reply #24 on: July 14, 2018, 08:46:35 AM »
after decades of using the centerstand I've relegated it now pretty much just for maintenance use.  Stories of it collapsing and general laziness are the culprits.  Two tricks to using the sidestand, tilt the bike to the right for a moment after shutting it off, and before starting it back it out of it's spot so you can drop it into gear and have a clean getaway, avoiding the glares and criticisms of onlookers and they succumb to a cloud of K smoke.  Actually, mine only smokes maybe 1 out of 10 times, no rhyme or reason.   :dunno
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
2012 Ural 2WD sidecar (BMW's bastard step child)

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