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K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » Getting "European horsepower" out of a US K75?

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roach374

roach374
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Has anyone had experience trying to get the European horsepower out of a US model K75? As I understand it, the American model was limited in order to comply with emissions standards. Is this a re-map of the ECU, a different CAM, or just plain impossible / not worth it?

    

Laitch

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According to Anton Largiader at Virginia Motorrad, the compression ratio was changed from 11.0:1 to 10.5:1 in 1986, lowering horsepower and torque, but it looks like the reduction happened to the K100 instead.



Last edited by Laitch on Sun Nov 29, 2020 4:05 pm; edited 1 time in total


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1995 K75 81,000 miles
Getting "European horsepower" out of a US K75? Usa-lo10
    

92KK 84WW Olaf

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Did they simply change to K100 pistons to do that or make a change to the head? 

Racing guys put K75 pistons into their K100 to increase the compression ratio.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 49,840 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

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I have always read and understood that K75 models - all years and markets - had 11.0:1 compression ratio both before and after the piston rings being 'pinned' for less oil burning when the end gaps would 'float' to the bottom allowing some oil to pass into the combustion chamber, circa 1988. As the bore is the same size as a K100 8V the K75 pistons slot right in. K100 8V had a 10.2:1 compression ratio.

For fun, here's a dyno run between a 1987 and a '92 K75...

Dyno Run Duelling K75

You might try disassembly of the stock TBs to fit three of the four 38mm K1200RS/GT (without cruise control) TBs, and then a reduced backpressure exhaust canister out back. No reason to change the air filter as the stock size does all the flowing it can. I once heard a rumour/theory/myth/outright lie that a K75 can reach 90 crank HP this way and one day I'm going to cobble one together like this to see if I can ruin its otherwise wonderful tractability this way.


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

5Back to top Go down   Getting "European horsepower" out of a US K75? Empty Horseypower Sun Nov 29, 2020 3:23 am

daveyson

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It's a while since I read up on it,  but I thought European horsepower was a reference to the k100, with earlier models having hotter cams, and later models different cams to comply with US exhaust regs (or was it Californie..i..a)

The higher compression for the k75 results in k75=75 horseys, easy to remember. The k100 doesn't reach that.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

brickrider2

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A K100 doesn't make 75 hp?  scratch


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1996 K1100LT
    

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brickrider2 wrote:A K100 doesn't make 75 hp?  scratch
Not in Switzerland, but, yes 90 crank HP in other markets.


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

8Back to top Go down   Getting "European horsepower" out of a US K75? Empty Horseypower Sun Nov 29, 2020 3:34 am

daveyson

daveyson
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True I meant the ratio,  if the k100 was as good it would mean k100=100horseys. I don't much remember numbers unless they're easy round ones.

Please don't ask me if 75 is a round number.



Last edited by daveyson on Sun Nov 29, 2020 3:37 am; edited 1 time in total


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Point-Seven-five

Point-Seven-five
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You gotta get the 16 valve version to get all 100.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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daveyson wrote:Please don't ask me if 75 is a round number.
Well, if we come at the task using numerology... 7 & 5 = 12. 1 & 2 = 3. 3 is a nice triangular, roundish number. Sold!


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

11Back to top Go down   Getting "European horsepower" out of a US K75? Empty Horseypower Sun Nov 29, 2020 3:50 am

daveyson

daveyson
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Pick a number between 1 and 10

Add 175

Subtract 75

Subtract the number you first thought of

By the magic power of round numbers the answer is 100

That's the number of horseys in a 16V K100. Coincidence?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Rick G

Rick G
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If you want horse power from a K75 get rid of the rev limiter they turn into little screamers Evil or Very Mad


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1986 K75 GS.
    

92KK 84WW Olaf

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daveyson wrote:It's a while since I read up on it,  but I thought European horsepower was a reference to the k100, with earlier models having hotter cams, and later models different cams to comply with US exhaust regs (or was it Californie..i..a)

The higher compression for the k75 results in k75=75 horseys, easy to remember. The k100 doesn't reach that.
Having 3 2v K100s, as in 83 K100RS, 84 K100RT and 92 K100LT.......the 83 and 84 Ks both have the vacuum sensor to advance ignition timing, the 92 K100LT does not have this. The 84 RT felt much more lively than the 92 LT.

But, the 83 RS is in a different league, cam profiles are the difference and it also has the visible engineering screws on the cam cover. Its much more lively than my K1100LT and I have 2 of those to compare it. I have not tried to find out if there is a difference in bhp....

I am only aware of 2 compression ratios, one for K75 and one for K100. Detuning is achieved by other means than altering pistons and compression ratios.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 49,840 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

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Directly below is a link to a prior discussion about K100-16V, K1 & K1100 camshafts. Post 18 is where I drew up a list of variables:

16V Camshafts link

Early K100 used 284 degree cams. They were still using these through 1989 on Std K100 and RS, and continued using them to the end of 8V production on LT/RT. California models 'always' used milder 256 degree cams. Swiss market K100 also used a 284 degree cam but with different part numbers.
11 31 1 460 045 Intake - Rest of the world
11 31 1 460 044 Exhaust - Rest of the world
11 31 1 461 525 Intake - CA
11 31 1 461 526 Exhaust - CA
11 31 1 464 000 Intake - Swiss
11 31 1 464 001 Exhaust - Swiss

I located an old parts official SNAB book (BMW's paper spare parts catalogue from before fische and ETK) on a back shelf at work the other day (printed late 1984) and it doesn't show a different part number on camshafts from early to late K100 models, either US or Rest of the World, as they used to list things. I think we're still being tugged and pulled at by that author from decades ago who suggested in jest at a rally seminar that the first year US 1985 (therefore, 1983, '84 & '85 Euro models) K100 were "the finest year". BTW, I was living near Greenfield Massachusetts when this rally was on but did not attend the seminar mentioned below.
As for why early models feel faster, it must be something in the water.


"Dave is absolutely correct. The story is kinda funny.

I was asked to give a K-tech session at the RA National Rally in Greenfield MA some years ago. (Dave was Chair of that rally..)

At the time, I owned an '85 K100RT, and was somewhat defensive about the scorn heaped upon the '85s by owners of later K's.

During the tech session, several people made somewhat disparaging remarks about the '85 K.. and finally in response to one of the remarks I sarcastically said "Oh - you mean the FINEST YEAR K?"

It got rather a large laugh and I thought that would be the end of it.. but I started referring to my K as the FYK100RT in messages to the IBMWR mailing list.

The name stuck. I started seeing it used in ads for '85 K bikes, it started appearing in people's SIGs on messages, and questions like this started popping up - "Why is the '85 the Finest Year K?" I've even seen it used in articles in a certain national club magazine Getting "European horsepower" out of a US K75? Clap

As Paul Harvey would say - now you know the rest of the story.. Getting "European horsepower" out of a US K75? Biggrin

Oh - the '85 K100's had one advantage over later K100's (until the 4V engine) - they were the "fastest" ones. They had a euro intake cam (except in California) that gave a real 90HP. Starting in '86 all K100's received the California intake cam (Edit: not true according to clear BMW ETK listings. California models were the only ones to have 256 cams both intake & exhaust) that gave about 5 less HP - but BMW never changed the specifications.

There were some features that BMW did improve with later K100's - heat management was generally better (but still awful on an RT) and buzz/vibration was reduced a bit... but the '85 bikes were a real bargain since you could usually find one for $1,000 or more cheaper than the same bike as an '86. This changed as the FYK rumour spread Getting "European horsepower" out of a US K75? Sad

Best, 
Don Eilenberger http://www.eilenberger.net 
Spring Lk Heights NJ NJ Shore BMW Riders"


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

Suzi Q

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That's a great, well-researched post.
Now I'm not saying anything to the contrary - I'm definitely not saying anything to the contrary.

But...
BMW have on occasion had the habit of upgrading a part, and leaving the part number unchanged. I know this because I had a problem with dropped valves on an oilhead boxer - long story - but it turned out that BMW upgraded/improved the valve spring retainer, which is obvious in comparison, but did not change the part number. They also modified the pushrods and made them heavier, but again no alteration to part number.

Now all of this was brought to my attention by someone in the trade. I've measured and seen the above two examples, but apparently, there are numerous other examples of this kind of carry-on from that Bayerischen crew. A cynic might conclude that it's a liability thing, but that'd just be a cynic's conclusion...

I've got an '84 K100 btw and it does go like stink, but then it has got a 89-onwards lighter crank.


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Sometimes I'm not really Suzi Quatro.
    

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It is absolutely true that Bay Em Vay change part designs without changing part numbers. To wit, the large, caged bearing in Paralever final drives is an example. When they were having dramas regularly with them they did not supersede the part number, even though the number of ball bearings inside changed. It was only years later that the number changed, after the hullabaloo of inherent bad design and subsequent failure had died down a bit. This could be a factor here with camshafts, might, perhaps, maybe, sure. WWNK.

Some years ago, whilst attending a BMW dinner in South Carolina after a yearly business meeting and test ride of the brand spanking new dog of a motorbike, the R1200CLC (I was a lowly parts manager but the dealer principal from our shop could not attend so he asked me to stay on for the business portion of the week), Frank Stevens from BMWNA, with a cocktail or three in him, was fielding questions from various shop owners. He said some remarkable things. One of them was an obvious, in reference to superseded part numbers, etc., "Do you expect us to open ourselves up to lawsuits!?"

Unless, someone has two previously untouched engines, from the years in question, apart and is willing to whip calliper and micrometre out and give 'em a bloody good going over to compare.

Chris846
"I've got an '84 K100 btw and it does go like stink, but then it has got a 89-onwards lighter crank."


10.3 kg (22.71 lbs) down to 8.95 kg (19.73 lbs) mid-year '89 production is a perty good ol' drop in spinning mass!



Last edited by Two Wheels Better on Sun Nov 29, 2020 11:49 pm; edited 1 time in total


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

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For further interest in the original subject, here's a list of K75 camshafts, all years, variants & markets. No degrees are included.

K75, C, RT, S
11 31 1 460 617 Intake
11 31 1 460 618 Exhaust

Why change a good thing?


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

Suzi Q

Suzi Q
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I get that too. I have 2 K7s at the mo - the madass and the K75k. Feel quite different - the K75k is punchy, but seems to take forever to rev out. Both are identical insofar as exhaust/intake/ignition advance etc. If the supercharger project comes to anything then I aim to dyno the engine before/during/afterwards, and educate myself. Seat of the pants can be very deceptive. Best example is messing with the intake: if (as is quite likely) you ruin the mid-range, then the sudden pick up when it starts to breathe properly/overcomes your handiwork/makes a lot more noise than before, can feel like a surge in power.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

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Often when someone at the shop enquires about go-fast goodies for their new Beemer or Ducati I first steer them towards thinking about weight savings. I'd love to sell you a Power Commander V & Termignoni full system, but eliminating that extra piled on plate at the all-you-can-eat-all-American-buffet table before your ride can make a world of difference. Some twig to what I'm suggesting, and I haven't been sucker punched yet.


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

Suzi Q

Suzi Q
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Life time member
Getting "European horsepower" out of a US K75? 44271


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Sometimes I'm not really Suzi Quatro.
    

Dai

Dai
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If you want to make the 100s go quicker for a couple of hours work, then do what quite a few on this forum have done (including me). Fit K1100 throttlebodies - you might need a new throttle cable too but that seems to be pot-luck on which cable quadrant you get on the tb stack - and advance the timing by six degrees (4mm on the hall sensor plate). The result is a shitload more punch in the midrange and it's not the ass-dyno kicking in. I compared an utterly standard '87 K100 back-to-back with my modified '83 K100, both equipped with RS fairings; at 50mph in third gear and nailing the throttle the standard bike felt like a paraplegic donkey.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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Yeah, Dai, I can confirm that that TB swap is ideal, 33mm for 35's. I did it ten years ago on my red K100RS. I never bothered to modify the TPS connection (or even hook it up) and with the slightly more free-flowing Motad exhaust it's a lively beasty when giving it a good caning at mid-RPM. It helps to have a modified ignition box, too. No rev limit means she sings into the red zone and keeps pulling. I once saw 255km/h (indicated) on a flat, dead-straight country road in New South Wales. I imagined errant wallabies and savoured the speed for only a little minute.


__________________________________________________

1970 R60/5, '77 R75/7-R100, '85 K100, '87 K75C, '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R, '04 R1150RT, '05 K1200S, #1 '06 K1200R, #2 '06 K1200R, '07 K1200R, '09 K1300GT, '13 R1200RT-P & 2022 S1000XR

"Do you ever read any of the books you burn?" "That's against the law!" "Oh, of course."
~Ray Bradbury, science-fiction writer (22 August 1920 - 2012)
    

Dai

Dai
Life time member
Life time member
Very Happy Saw that speed come up on a Moto Guzzi Daytona 'B' once and it was still pulling...then I threw the bloody big anchor out the back in a panic because the roundabout on the horizon wasn't on the horizon any more affraid affraid affraid  Nowadays that particular dual carriageway down in Dorset is more often nose-to-tail than clear. A bit more dangerous than wallabies.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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