BMW K bikes (Bricks)

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1Back to top Go down   Is my throttle response normal? Empty Is my throttle response normal? Tue Sep 06, 2016 12:50 pm

Bikesmith

Bikesmith
Silver member
Silver member
Hey gang!
    Thanks to all your help, I have my 1985 K100 RS running incredibly well. It seems pretty much perfect at this point. There's just one thing I'm wondering about:
    When I release the throttle, the transition from engine powering to engine braking seems abrupt and strong. If I let the throttle off as slowly as I can, engine power eases off just as I would expect right up until the end, when it suddenly jumps to very strong engine braking (enough to make the front end dive if I do it in 1st). Is this perhaps an actual problem, or just a case of me needing to get used to how this engine works?
    The transition in the other direction (beginning to apply throttle) is also sharp, but I can manage it if I'm very careful with twisting the throttle.
    Also, the bike idles a little high (1050-1100). My thinking is that that's not causing the problem. If anything, it seems like that might have been an attempt on the part of the previous owner to ease the power-to-braking transition. Am I wrong? Could that be causing an issue?
    Overall, it's not really a big deal. I think mostly I'm noticing this because I'm used to a 76-year-old, softly tuned, 13HP 350cc engine. So the K100 engine feels REALLY strong to me. But now that I've fixed all the real problems, I'm free to obsess about things that probably aren't actually problems.
    Thanks again for all your help!
    -Jon


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

2Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Tue Sep 06, 2016 1:35 pm

JGT

JGT
Gold member
Gold member
Sounds like you need to disable the TPS switch.

    

3Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Tue Sep 06, 2016 2:08 pm

Bikesmith

Bikesmith
Silver member
Silver member
Yeah, thanks for the tip! I just read a bunch of posts about disabling the TPS. Sounds like that's just what I'm looking for!


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

4Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Tue Sep 06, 2016 5:23 pm

WoodyAUK75

WoodyAUK75
Silver member
Silver member
I also thought my K idled too high, but read somewhere that it needs to be idling over 1000rpm to supply enough current to the computer. I have heard different since, but I'm sure others will chime in.

    

5Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Tue Sep 06, 2016 6:06 pm

Bikesmith

Bikesmith
Silver member
Silver member
Clymer manual says 900-1000rpm. I'll get around to adjusting it one of these days, but it's such a trivial problem that I haven't bothered yet.
  My to-do list started with items like 'Replace Hall Sensor', 'Replace Fuel Pump', 'Replace Final Drive Ring Gear Seal'. Then it progressed to items like 'Upgrade Radiator Fan', 'Install Headlight Relay', and 'Grease Clutch Splines'. Now it's down to things like 'Replace Grips', 'Calibrate Speedometer', and 'New Sidestand bushing'.
  So, yeah, the idle adjustment is coming soon. really. Wink


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

6Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 4:09 am

charlie99

charlie99
VIP
VIP
to adjust the tps   ....undo the two retaining screws (I have changed mine to allen head types rather than the Philips screws far easier to adjust whilst on the bike )
and rotate the tps anti clockwise .... looking from the coil covers
just enough so that you no longer here the click as the throttle is closed .......works for me
but give it a try ..
good luck


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OIs my throttle response normal? Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

7Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 5:07 am

AL-58

AL-58
Life time member
Life time member
The fuel cutoff gven by the TPS would probably feel more abrupt with a high idle. Likely feel a whole lot different with idle and TPS set correctly. 

I know that my RT doesn't feel like a sudden cut, either decelerating or accelerating with a completely functional TPS. The transition is barely noticable.

Al


__________________________________________________
'87 K100RS/HRD sidecar (1100 motor)  sc25 

'87 K100RT with Paralever backend

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

Is my throttle response normal? K-dogs10
    

8Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 11:55 am

Holister

Holister
Life time member
Life time member
That's an interesting observation/comment Al. Can't say that I've made that connection myself before, but it certainly sounds like a very plausible explanation.
One thought I've had is that this abrupt change could be due in part to FD spline wear which creates free movement between the input and output splines.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Is my throttle response normal? Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

9Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 5:59 pm

duck

duck
Life time member
Life time member
There's already some play in the drive train even with brand new FD splines. I doubt FD spline wear would be noticeable when riding.


__________________________________________________
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
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

10Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 7:11 pm

Shep

Shep
Gold member
Gold member
Would someone give a brief explanation of the TPS switch please.
Shep


__________________________________________________
Model        Production Date/Serial Number
K100RS      1984 July/ (F0040448)
K100RS      1986 Dec/ (H0142581)
    

11Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 7:22 pm

klompy the grey brick

klompy the grey brick
VIP
VIP
@charlie99 wrote:to adjust the tps   ....undo the two retaining screws (I have changed mine to allen head types rather than the Philips screws far easier to adjust whilst on the bike )
and rotate the tps anti clockwise .... looking from the coil covers
just enough so that you no longer here the click as the throttle is closed .......works for me
but give it a try ..
good luck
Spot on Charlie....if you have to have a functioning TPS. Personally I disconnected mine.

KKlompy


__________________________________________________
KKlompy Is my throttle response normal? 2854237993
"Grace" 1984 K100RS Silver VIN 0019026 Mitt eine Staintune Zorst.
"Olivia" 1997 K1100LT Dark Grey VIN WB1052600W0237453.









Chassis number0019026
Vehicle code0503
SeriesK589
ModelK 100 RS 83 (0502 ( 0503 )
Body typeK 100 RS 83 (0502
Catalog modelECE
Production date1984 / 07
Engine0513)

Is my throttle response normal? Au-log10


    

12Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 8:26 pm

RicK G

RicK G
admin
admin
@Shep wrote:Would someone give a brief explanation of the TPS switch please.
Shep
Throttle Position Sensor. On a K100/75 2V it gives a signal to the Engine Control Unit of the position of the throttle but only closed and wide open where on later models it gives feedback through out the full range of throttle movement.


__________________________________________________
"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, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

13Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Wed Sep 07, 2016 9:38 pm

kennybob

kennybob
Silver member
Silver member
TPS signal functions:

When the throttle is let closed while travelling, the fuel injection is turned off until the rpm drops below about 2000.  aka closed-throttle overrun, prevents popping of excess fuel in the exhaust.

When the throttle is opened off of the TPS closed position, the ignition timing is advanced, to provide low-end torque and power to get moving.

At WOT, wide open throttle, the fuel injection goes richer and the ignition timing gets advanced for maximum power.

    

14Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Sun Sep 11, 2016 5:06 am

RedRT

RedRT
active member
active member
(enough to make the front end dive if I do it in 1st).
Could that be an effect of the shaft drive system?

    

15Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Sun Sep 11, 2016 5:17 am

charlie99

charlie99
VIP
VIP
to me the rt ..lt suffers the worse for the tps function
perhaps it is to do with the riding position and the weight and travel of the front suspension
the k75 front suspension seems to have a much lower travel and different springing and damping characteristics

just some things I have noticed along the path


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OIs my throttle response normal? Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

16Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Sun Sep 11, 2016 8:01 am

Holister

Holister
Life time member
Life time member
@RedRT wrote:(enough to make the front end dive if I do it in 1st).
Could that be an effect of the shaft drive system?
Best thing to do is simply adjust it so its not functioning. 2min job.

  1. Undo the two screws either side. You'll need a short screwdriver or a rachetty phillips head drive thingy.
  2. Turn TPS counterclockwise till you here the micro switch click.
  3. Tighten screws.


When its working properly you should be able to hear it click juuuust as you open the throttle.

I don't seem to have that 'diving' problem that others have reported. Maybe my front susp. is stiffer. Either way, I prefer the TPS working. Better engine braking.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Is my throttle response normal? Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

17Back to top Go down   Is my throttle response normal? Empty Re: Is my throttle response normal? Mon Sep 12, 2016 1:15 pm

Bikesmith

Bikesmith
Silver member
Silver member
TPS Report:
    I adjusted the TPS to be inactive at the idle end. I used exactly the technique that Holister described. Super easy job and it made a world of difference, just as others have reported. A MUCH smoother transition both letting the throttle off and bringing it back on. There's still ample engine braking. There's still feedback from the bike when the engine switches from power to braking. But it's a nudge instead of a jolt. It's perfect. And I don't look like a complete lurching idiot trying to go around a low-speed corner anymore, which is nice.
   That's all pretty much what I expected based on reading other threads on this topic. Here's the part I didn't expect: My high-idle problem is gone. The bike is idling perfectly about a needle's width below 1000rpm. I had noticed before that the throttle body control arm was never touching the idle adjustment screw. I figured that the pivot was sticky, or the throttle cable had issues (even though it felt dead smooth), or something like that. It was the TPS. I'm not exactly sure how, but it was preventing the throttle from being able to back off all the way to the idle screw. Now it's fixed. Yay!


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

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