BMW K bikes (Bricks)


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Puccini

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1985 K100RT

Whats the function of the throttle position switch?

Also I've been having some occational missing that lasts a short time , usually on acceleration.

I replaced the fuel filter that was old and it improved but it still happens from time to time.

I feel it's still the fuel system.

I had the injectors cleaned and replaced the fuel lines in the tank and on the bike recently.
New plug wires and plugs.

Cleaned every contact I could find under the tank and on  the computer.

Once at speed the bike runs perfectly.
Lots of smooth power.

Mileage estimate is about 30,000 mi.


Any suggestions.

    

Kyle10

Kyle10
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Puccini, 

Here's just a cupla threads worth reading for edification. Use the search function field, as this is the best forum for Kollective wisdom:

Things that BMW put there to annoy me (2010)

K100rs Throttle Position Switch info?

I've been running w/o mine for some time now and none the worse for wear (seemingly).


__________________________________________________
1985 K100rt 0052183
1983 Honda VF750 007713 
    

Comberjohn

Comberjohn
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Firstly, you can eliminate the TPS by unplugging it and trying the bike.
It's designed to help anti pollution measures but will run without it.
When decelerating, it cuts the fuel until below 2000 rpm and enriches it at full throttle.
Some find is smoother without it. I did. There are threads about the pros and cons of using it.
Does the misfire appear after the engine warms up?
Could be the ignition triggers behind the T shaped cover on the front of the engine. If you heat them with a hair dryer when the engine is cold and the misfire is there immediately. That's the problem.
Not unheard of.
Other possibility is, are you using resistor spark plugs with resistor leads? 
There'll be be more suggestions soon.
The inmates here like a problem.


__________________________________________________
Life is not a rehearsal.
2010 VFR 1200F DCT 
2010 R1200GS(gone)
1986 K100 Silver(gone)
2012 K1600GT(gone)
1984 K100RT Madison Silver(gone)
1989 K100LT Stratus Grey(gone)
1984 K100 Red(gone)
http://www.johnsdrivingschool.co
    

Puccini

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Comberjohn wrote:Firstly, you can eliminate the TPS by unplugging it and trying the bike.
It's designed to help anti pollution measures but will run without it.
When decelerating, it cuts the fuel until below 2000 rpm and enriches it at full throttle.
Some find is smoother without it. I did. There are threads about the pros and cons of using it.
Does the misfire appear after the engine warms up?
Could be the ignition triggers behind the T shaped cover on the front of the engine. If you heat them with a hair dryer when the engine is cold and the misfire is there immediately. That's the problem.
Not unheard of.
Other possibility is, are you using resistor spark plugs with resistor leads? 
There'll be be more suggestions soon.
The inmates here like a problem.

Misfire seems to happen when bike is up to temp and ridden for a while.

Plugs are correct non resistor types with the stock BMW caps and wires

    

Comberjohn

Comberjohn
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Sounds like the ignition triggers otherwise known as the Hall effect sensors.
Think someone recently mentioned a reasonably priced alternative to the BMW originals. Second hand ones are now getting quite old and are liable to fail, if they haven't already.
If you do a search for 'hall effect' on the forum search you'll get plenty of info.
If anyone has any other suggestions about the possible cause I'm sure they'll mention it but that sounds like the most likely.


__________________________________________________
Life is not a rehearsal.
2010 VFR 1200F DCT 
2010 R1200GS(gone)
1986 K100 Silver(gone)
2012 K1600GT(gone)
1984 K100RT Madison Silver(gone)
1989 K100LT Stratus Grey(gone)
1984 K100 Red(gone)
http://www.johnsdrivingschool.co
    

Puccini

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Silver member
Thanks for the info.

Gerry

    

Holister

Holister
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After warm up and a base fuel injection time is reached, the FICU has 3 modes, idle, partial load and full load and enrichens fuel injection to suit the demand by increasing injection times. these 3 modes aretriggered by the TPS.

Idle mode is triggered when the throtle is closed and revs are below 2k. There is no enrichment to the base fuel injection times except to compensate for temp and air etc etc. The 'throttle closed' position switch is open (ie continuity). If engine revs are above 2k with throttle off, the FICU cuts injection completely untill below 2k.

Partial load mode is triggered when the throttle is opened. This enrichens the mix slightly to cope with normal running at higher revs. The 'throttle closed' position switch is now open (ie no continuity).

Full load mode is triggered when the throttle is fully opened. This enrichens the mix further to provide hard acceleration. The 'throttle fully open' position switch is now closed (ie continuity).

You can disconnect the TPS without any adverse effect but the 'throttle closed' and 'throttle fully open' switches will in effect be considered open (no continuity) by the FICU. This will result in...

  • The FICU will operate in partial loade mode while idling. No big problem but you'd need to consider this when tuning the engine.
  • Base fuel injection will be maintained instead of being cut when 'throttling off' (closed throttle at speed, engine above 2k) which will reduce the effect of engine braking. Some like this because it's a smoother transition when throttling off. You'll get slightly less tyre wear on the rear but you may find the need to use front bakes more. This is really going to be down to personal preference.
  • Partial load mode will operate as normal but you will not get full lode enrichment when the throttle is fully opened. No biggie either unless you're a rev-head or maybe one day you need that little extra to get yourself out of a situation.


Hope this helps.

Re the misfire. Worth checking the coils and easy to do. They can malfunction when warm.
Cracked casing will cause earth leak. Lightly sparay coils and leads with water/detergent with garage door down.
Windings may be shorting. There are posts which outline how to test the impedance of the coil winfings and leads etc. Just use the Google/forum search box on the portal tab



Last edited by Holister on Tue Oct 04, 2016 3:27 pm; edited 2 times in total (Reason for editing : corrections)


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Whats the throttle position switch for? Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

Puccini

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Silver member
Silver member
Kaptain Holister wrote:After warm up and a base fuel injection time is reached, the FICU has 3 modes, idle, partial load and full load and enrichens fuel injection to suit the demand by increasing injection times. these 3 modes aretriggered by the TPS.

Idle mode is triggered when the throtle is closed and revs are below 2k. There is no enrichment to the base fuel injection times except to compensate for temp and air etc etc. The 'throttle closed' position switch is open (ie continuity). If engine revs are above 2k with throttle off, the FICU cuts injection completely untill below 2k.

Partial load mode is triggered when the throttle is opened. This enrichens the mix slightly to cope with normal running at higher revs. The 'throttle closed' position switch is now closed (ie no continuity).

Full load mode is triggered when the throttle is fully opened. This enrichens the mix further to provide hard acceleration. The 'throttle fully open' position switch is now open (ie continuity).

You can disconnect the TPS without any adverse effect but the 'throttle closed' and 'throttle fully open' switches will in effect be considered closed (no continuity) by the FICU. This will result in...

  • The FICU will operate in partial loade mode while idling. No big problem but you'd need to consider this when tuning the engine.
  • Base fuel injection will be maintained instead of being cut when 'throttling off' (closed throttle at speed, engine above 2k) which will reduce the effect of engine braking. Some like this because it's a smoother transition when throttling off. You'll get slightly less tyre wear on the rear but you may find the need to use front bakes more. This is really going to be down to personal preference.
  • Partial load mode will operate as normal but you will not get full lode enrichment when the throttle is fully opened. No biggie either unless you're a rev-head or maybe one day you need that little extra to get yourself out of a situation.


Hope this helps.

Re the misfire. Worth checking the coils and easy to do. They can malfunction when warm.
Cracked casing will cause earth leak. Lightly sparay coils and leads with water/detergent with garage door down.
Windings may be shorting. There are posts which outline how to test the impedance of the coil winfings and leads etc. Just use the Google/forum search box on the portal tab
OK, here's a question. Is it possible to disable the TPS "throttle closed" position and still leave the TPS "throttle full" position switch active so you can get that extra punch at full throttle if you need it?

    

Holister

Holister
Life time member
Life time member
When the TPS is set correctly, the throttle closed switch should click off juuust as you apply light throttle. You'll hear it click.
To disable simply loosen the fixing screws and turn the TPS unit counter-clockwise juuust till you hear the switch click off. Tighten the fixing screws. You should now not be able to hear the throttle closed switch click as you open the throttle.

Personally, I prefer it on because I feel I get better control/handling going into corners, especially at speed. A bike will corner much better when either accelerating or decelerating (not braking!!). Just my thoughts

Cheers.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
 Whats the throttle position switch for? Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

Comberjohn

Comberjohn
Life time member
Life time member
The inner screw on the TPS can be a bugger to get at when trying to loosen it to adjust.
Or you can just cut the black/white wire. Try to leave enough wire to reconnect again. It was discussed that putting a switch in somewhere on that wire would give you the choice of both modes.
Personally, I never had any desire to go back to that on/off feeling that it gave and prefer the smooth deceleration.
You need to unplug it and try it yourself to see which you prefer.


__________________________________________________
Life is not a rehearsal.
2010 VFR 1200F DCT 
2010 R1200GS(gone)
1986 K100 Silver(gone)
2012 K1600GT(gone)
1984 K100RT Madison Silver(gone)
1989 K100LT Stratus Grey(gone)
1984 K100 Red(gone)
http://www.johnsdrivingschool.co
    

Puccini

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Silver member
Silver member
Really good advice here.
Thanks for the help.

    

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