BMW K bikes (Bricks)


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duck

duck
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If you believe so then make your case with facts and/or data.

a) different part numbers

b) dyno tests

c) measured cam profiles


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

92KK 84WW Olaf

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Well, my understanding is the cam profile changed and part no did not change. I have seen this on a number of K parts where they were modified in the production run, after buying brand new and used parts based on part nos. Very early Ks don't have the same front calipers! Smaller pistons! Seems they came out of the R bike parts bins...like the push button fuel cap...

I am tempted to do dyno tests as I have 3 Ks that fit the category of early Ks. I also have an early engine I could dismantle. I have a very lively K1100 to compare them to, their performance above a certain speed is definitely superior to the K1100 and very silky smooth. 

For the time being all I have been able to do is ride them back to back and with similar conditions as in fresh air filters, same injectors etc.


__________________________________________________
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 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 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
    

Rick G

Rick G
admin
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The K100s that were sent to North America had different intake cams. The intake opened 20° later than the European models.
This has the effect of lowering the compression at lower engine speeds and a slight reduction in burn temperature which in turn reduces the nitrogen oxides produced.
It was the emission standards in California that was the reason and the rest of North America had to follow along.
There was a very slight reduction in low end torque and a very slight reduction of Horse Power in the top end, most riders would not pick the difference.
I am not sure if the K100s sent to the rest of the world had the same cams fitted at that time.
I have posted the numbers many years ago here and on the Motobrick forum.
As for the cams being "hotter" don't waste your time changing them or trying to get some it would be a wasted exercise.


__________________________________________________
"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 1999 K1100 LT with a Big Block 1200
    

glennpm

glennpm
Silver member
Silver member
Rick G wrote:The K100s that were sent to North America had different intake cams. The intake opened 20° later than the European models.
This has the effect of lowering the compression at lower engine speeds and a slight reduction in burn temperature which in turn reduces the nitrogen oxides produced.
It was the emission standards in California that was the reason and the rest of North America had to follow along.
There was a very slight reduction in low end torque and a very slight reduction of Horse Power in the top end, most riders would not pick the difference.
I am not sure if the K100s sent to the rest of the world had the same cams fitted at that time.
I have posted the numbers many years ago here and on the Motobrick forum.
As for the cams being "hotter" don't waste your time changing them or trying to get some it would be a wasted exercise.

I found that changing my USA '87 K100RS with an '85 intake and exhaust cams made a noticeable difference. A friend at the time also has a K100RS and we switched bikes for a test. He said, "I wish mine went like that!"

Glenn



Last edited by glennpm on Sat Nov 02, 2024 8:50 am; edited 1 time in total

    

92KK 84WW Olaf

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Life time member
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Rick G thank you for that post.

Your comment about the top end is precisely where I notice the difference.

The vacuum sensor fitted to early Ks, perhaps its where it has some effect. Everyone agrees 'it does nothing' and they do run fine without it but maybe it did something at the top end.


__________________________________________________
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 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 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
    

glennpm

glennpm
Silver member
Silver member
More info from my old notes:

These are the number from Max's
http://www.maxbmwmotorcycles.com/fiche/diagrams.asp?mospid=45546&VIN=&hg=11&fg=3
0&model=K100RS

-01 11 31 1 461 525 Inlet Camshaft 256 GRAD 
-01 11 31 1 460 045 Inlet Camshaft 284 GRAD  - 1985 High Lift Intake

-02 11 31 1 461 526 Camshaft Exhaust 256 GRAD
-02 11 31 1 460 044 Camshaft Exhaust 284 GRAD - 1985 High Lift Exhaust

Duration for high lift = 284°
Duration for NA lift   = 256°
284° - 256° = 28° longer duration

1985 Camshaft Specs
-------------------

The base diameter is 1.18"

The height difference is 0.04 to .05"

Standard is 1.50"

1985 cam is 1.54 to 1.55"

1.50 - 1.18 = .32 lobe lift
.32 + .04 or .05 = .37

.37/.32 = about 15 % more lift

***********

"The K100s that were sent to North America had different intake cams. The intake opened 20° later than the European models" (Rick G)

"Around April of 1985 BMW began selling a 50 state legal bike in the US (note: there was never a "California" model as such). These came with 256 degree cams, costing 7 horses and taking away some of the original top end rush." (TheMason)

"I believe the only difference on the cams were between the 85 and 86 model. The 85 has 10 more HP." (Crazy Frog)

****


Glenn



Last edited by glennpm on Mon Nov 04, 2024 3:37 pm; edited 4 times in total (Reason for editing : Added quotes)

    

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