BMW K bikes (Bricks)

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1Back to top Go down   [solved]Speed and revs Empty [solved]Speed and revs on Sat Oct 12, 2019 7:37 am

tinyspuds

tinyspuds
Silver member
Silver member
Hi all,
My 8 valve 100RT (60k miles) with a double adult chair feels reluctant to spin up over 4000 rpm.
At those revs I’m seeing about 65mph (100 kph) in top.
From all I’ve read that doesn’t sound right even with a heavy sidecar. 

The bike runs well in all other regards and mpg is a consistent 10 miles per litre.

Before starting diagnosis I had the valves shimmed back to spec. which has made the engine feel and sound better but hasn’t changed these two numbers.
It may be that I’m just backing off the gas too early (my other bikes are brit single and Big V so I’m not a natural revver). 

Before I start pushing rpm out of my comfort zone, any words of advice/caution?

Any views from our sidecar brethren on what I should be expecting to achieve through the gears.

Cheers, Stu


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s.
2007 HD883 Sportster. Bobbed and bettered.
1954 Royal Enfield 350 Bullet. Original.
    

2Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 8:04 am

duck

duck
Life time member
Life time member
Words of advice: Don't worry about high RPMs.

Ks are high rev engines. Run it up to 8500 RPM and bounce it off of the rev limiter just to feel what it's like. You won't hurt anything.


__________________________________________________
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 (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

3Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 8:06 am

RicK G

RicK G
VIP
VIP
The only thing that will change those numbers is a change of gearing in the read drive. Tyre size will make a slight difference.
The engine is limited to 8400RPM by a rev limiter in the ignition control unit. Reving them hard will use more fuel but wont hurt the engine.


__________________________________________________
"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 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

4Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 8:10 am

Dai

Dai
Life time member
Life time member
According to BMW themselves (via Mick Walker's book 'BMW K-Series') the engine was designed to cope with 170hp+. You ain't gonna break it, unless you really try hard. Third gear, big handful and hold on to the throttle. On a solo that gets you into the fun zone... Very Happy


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

5Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 8:38 am

duck

duck
Life time member
Life time member
Here's the power curve for the K100. When you've got the throttle pinned and you're paying attention you will feel it peak at about 6000 RPM.

[solved]Speed and revs XTlbFvA


__________________________________________________
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 (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

6Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 9:21 am

Laitch

Laitch
Life time member
Life time member
Here is speed/gear data computed using a 2.91 final drive/K100 transmission as output from Anton Largiader's interactive final drive comparison table. A 3.00 will be slightly less steep.

[solved]Speed and revs K100_212


__________________________________________________
1995 K75 73,000 miles
[solved]Speed and revs Usa-lo10
    

7Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 2:11 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
65 mph at 4000rpm sounds about right for RT final drive gearing.  5000 should get you about 75mph, and at six grand you should be nicely up into the mid 80's.

Like the others have said, you need to learn to get the revs up.  These engines will run all day at the redline and love it.  I've read that these engines have been run in the factory for 24 hours at full load at 8500 rpm.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
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
    

8Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 5:01 pm

tinyspuds

tinyspuds
Silver member
Silver member
Love you guys. Every tech issue I’ve had you’ve given me deep engineering and experienced based guidance. Power curve question, you revert to big kids [solved]Speed and revs 723598[solved]Speed and revs 44271


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s.
2007 HD883 Sportster. Bobbed and bettered.
1954 Royal Enfield 350 Bullet. Original.
    

9Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 5:03 pm

tinyspuds

tinyspuds
Silver member
Silver member
PS. I’ll go with your flow: gun it.


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s.
2007 HD883 Sportster. Bobbed and bettered.
1954 Royal Enfield 350 Bullet. Original.
    

10Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sat Oct 12, 2019 6:32 pm

Dai

Dai
Life time member
Life time member
Dragon tickets are on sale... (hint). Good excuse to gun it .


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

11Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Sun Oct 13, 2019 12:32 am

tinyspuds

tinyspuds
Silver member
Silver member
@Dai wrote:Dragon tickets are on sale... (hint). Good excuse to gun it .
Ordered last week. I’m sorting out some better lighting, heated grips, starter motor clean and spline lube. Assuming I don’t mess up, see you there.


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s.
2007 HD883 Sportster. Bobbed and bettered.
1954 Royal Enfield 350 Bullet. Original.
    

12Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Mon Oct 21, 2019 7:37 am

AL-58

AL-58
Life time member
Life time member
My 1 and a half sidecar on K100RS (RT final drive, 1100 motor and 165/15 rear tyre) runs 5000rpm at 120kmh (75mph), its what they do. 5000 on a four sounds twice as busy as 5000 on a twin as there are twice as many firing strokes.

Not a fan of revving mine hard either but I don't have to either other than open highway.  I rarely run it over 5000, it goes well enough at those revs anyway. I dont find any advantage at all in revving it higher, just makes more noise.

At 10 miles per litre (16km/l) you are doing pretty well on a sidecar already.  Mine will do that on a good day, but usually a bit less.

Al


__________________________________________________
'87 K100RS/HRD sidecar (1100 motor)  sc25 
'92 K100RS-16v (Paint it Black)

'87 K100RT with Paralever backend

"When I'm too old and too foolish to handle a sidecar I'll buy a Sportsbike"

[solved]Speed and revs K-dogs10
    

13Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Mon Oct 21, 2019 11:21 am

tinyspuds

tinyspuds
Silver member
Silver member
Thanks everybody,
I’ll stop fretting. I crossed my fingers and ran the motor gently up to 6 thou. So now I know it will do it I just need to train myself to push it a little harder.
Onwards with the Winter maint.
Stu


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s.
2007 HD883 Sportster. Bobbed and bettered.
1954 Royal Enfield 350 Bullet. Original.
    

14Back to top Go down   [solved]Speed and revs Empty Re: [solved]Speed and revs on Mon Oct 21, 2019 3:39 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
At some ppint in time you will be tooling along happily at 120kph, look down, and find you are in 4th gear.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
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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