Motor will only run at idle speed

[Cafe racer]

First off, is this the right place to post a HELP question...
after about 30 mins of riding, the bike suddenly lost power, I could only rev to about 1000 rmp.
I have checked the fuel pump, I can hear it running. but still only 1000 rmp.
a little history, two days prior after about 1 hours riding I turned off the ignition and the fuel pump continued to run....so I turned back on and started the bike, then turned off again, this time the pump stopped. I am now waiting for a jerry can to arrive so I can drain the tank and remove the pump and check the filter etc...
BUT.... in the meanwhile has anybody got an ideas !!!!!

K100RS 1988 2V

[Scott_]

When you in there checking the filter, make sure all of the hose fittings are on tight.
How well does it run at idle speed, is it smooth, or rough.
You should also check the TPS wiring plug and operation. You will find instructions in the tech library.

[Laitch]

I turned off the ignition and the fuel pump continued to run....so I turned back on and started the bike, then turned off again, this time the pump stopped.

This might be a function of temporarily stuck contacts in the fuel pump relay. It might have been a one-off occurrence that won't happen again.

[Laitch]

What is the battery's resting voltage?

[Cafe racer]

What is the battery's resting voltage?

I will pick up my multimeter at the weekend and get back to on that...

[Cafe racer]

When you in there checking the filter, make sure all of the hose fittings are on tight.
How well does it run at idle speed, is it smooth, or rough.
You should also check the TPS wiring plug and operation. You will find instructions in the tech library.

Idle is smooth but try to go above 1000 rmp and its rough and wants to stall.
Remind me what the TPS is LOL
Tech library.... now where are my glasses...

[Martin]

Get it to stall and then pull the spark plugs. Are they wet or dry?
Regards Martin.

[Cafe racer]

Get it to stall and then pull the spark plugs. Are they wet or dry?
Regards Martin.

Hi Martin, certainly not wet...My jerry can and pump should arrive today, then I will drain the tank, pull the pump etc and start some serious investigation

[Scott_]

Idle is smooth but try to go above 1000 rmp and its rough and wants to stall.
Remind me what the TPS is LOL
Tech library.... now where are my glasses...

In your case "TPS" Throttle Position Switch...
Tells the computer when the throttle is at the closed(idle) position, and when the throttle is equal or greater than 75% open.

You might also check and make sure that the air flow sensor is not stuck in the closed position.

The TPS and AFS both affect how the fuel injection computer controls the injectors/fuel flow.

[volador]

What is the history of this moto, what mileage? Is this a stock 1988 K100RS or cafe'd?

During normal riding 30mins or more does the cooling fan cycle on/off?

After normal riding 30mins or more then loss of power is suspect to a intermittent failure of Hall Effect Sensor.

The test for this is done with a heat gun or a really good hair-dryer. The hall effect sensor assembly lives behind the T shaped cover on the right (facing forwards – starboard side of the engine. The cover is removed with allen wrenches.

The test – let the engine idle – and direct the heat gun at the Hall-effect sensor. If it cuts out when it gets good and warm – this is a big clue. Then turn the heat gun to just blowing air and cool it, try restarting. If it restarts, this is the 2nd clue. You may want to do this test a number of times to make certain it’s the fault.

The hesitation at higher RPMS indicates a weak spark, caused by a partially failed HES. The complete cutout indicates complete ignition failure – again, pointing (when combined with the hesitation) to the HES.

Electrical gremlins or instances of intermittent electrical problems can be caused by carbon deposits in the starter motor.

STARTER MOTOR REBUILD

Starter Backspin

Robmack's Starter Motor Cleaning Tutorial

OTHER THINGS TO LOOK AT:

Coils – look at them in the dark with the bike idling, just to make sure there isn’t a crack in the towers that is causing arc-over.
 
Ignition wires – worth checking the resistance on them. The wires should be 6k Ohms end to end.

The K100 is originally fitted with Bosch X5DC spark plugs (or can be fitted with the NGK D7EA). Both are non resistor spark plugs: The original BMW spark plug cap already integrates a resistance of 5KΩ. Similarly, the connector at the other end of the original ignition cable also includes a resistance of 1KΩ (The total resistance is 6KΩ).

Poor seating of the FI computer connector. More than one intermittent K bike problem like this has been fixed by re-seating the connector on the FI computer. Easy to do, and no cost at all.

Ignition switch or kill switch partial failure. Some people have had problems with deposits on the ignition switch causing intermittent running problems, cleaning it is the cure.

Ignition Switch Cleaning
   

Some links for your K journey

Just bought a 2V

Just bought a 4V

Check parts compatibility with BMW MAX Microfiche, BOBS BMW, REAL OEM

https://shop.maxbmw.com/fiche/PartsFiche.aspx

https://shop.maxbmw.com/fiche/PartsSearch.aspx

https://parts.maxbmw.com/BMW___BmwMotorradK.html

https://www.bobsbmw.com/store/microfiche/BrowseSeries.aspx

https://www.realoem.com/bmw/select.do?kind=M&arch=1

https://www.ascycles.com/BMW-Motorcycle-Parts-Fiche

Cross reference parts like Bosch pn#'s, etc....  http://partsplusecat.com/
No spaces in the part number

Parts Vendors

https://www.beemerboneyard.com/

https://www.capitalcycle.com/

https://www.euromotoelectrics.com/

https://www.tills.de/

Headlight relay stuff if you chose to add one

https://www.motobrick.com/index.php?topic=268.0

http://www.motobrick.com/index.php/topic,4962.msg30932.html

http://culayer.com/product/matchbox-headlight-relay/

http://easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html  Eastern Beaver site is a great reference for electrical connectors,plugs, etc...

http://www.k100-forum.com/

http://www.kforum-tech.com/Tech-page.html

http://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm

http://www.kforum-tech.com/Downloads/electrical/diagrams/interactive_diagrams.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/k100tshoot/K100.Troubleshoot.Start.2018.pdf

http://kbikeparts.com/index.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/ckb.new2k.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/ckb.tech.toc.htm

http://www.eilenberger.net/K75S/IgnitionSwitch/

http://www.verrill.com/moto/moto.shtml

this site has a lot of good info and breakdown pictures in the tech and tech resources sections for K1100 alot of the parts are on K75 & K100

http://www.k11og.org/forum/index.php?sid=2df953dde5715fd9001fbe69edec5ad0

https://ibmwr.org/index.php/k-bike-tech-articles/

This site has all kinds of technical specifications on all the BMW models    http://www.bmbikes.co.uk/mechanicalpages/kseriesmechanical.htm

http://largiader.com

http://bmwk10075abs1fix.web.fc2.com/index.html  Toshi ABS site

Hosa D5S-6 CAIG DeoxIT 5% Spray Contact Cleaner, 5 oz.

CAIG Laboratories D100L-25C Contact Cleaner Needle Dispenser

Water Pump
pre-1986-87? original design old style impeller 11411461177

Superseded by 11412325850 design change the shaft with gear Z=32 teeth, shaft- 11411461183

Superseded by 11417676366 same shaft with gear Z=32 teeth

latest design 11517676371 design change shaft with gear Z=19 teeth, shaft- 11411461793

[Cafe racer]

What is the battery's resting voltage?

Voltage at rest is 12.37.

[Cafe racer]

What is the history of this moto, what mileage? Is this a stock 1988 K100RS or cafe'd?

During normal riding 30mins or more does the cooling fan cycle on/off?

After normal riding 30mins or more then loss of power is suspect to a intermittent failure of Hall Effect Sensor.

The test for this is done with a heat gun or a really good hair-dryer. The hall effect sensor assembly lives behind the T shaped cover on the right (facing forwards – starboard side of the engine. The cover is removed with allen wrenches.

The test – let the engine idle – and direct the heat gun at the Hall-effect sensor. If it cuts out when it gets good and warm – this is a big clue. Then turn the heat gun to just blowing air and cool it, try restarting. If it restarts, this is the 2nd clue. You may want to do this test a number of times to make certain it’s the fault.

The hesitation at higher RPMS indicates a weak spark, caused by a partially failed HES. The complete cutout indicates complete ignition failure – again, pointing (when combined with the hesitation) to the HES.

Electrical gremlins or instances of intermittent electrical problems can be caused by carbon deposits in the starter motor.

History
Bike is a standard 1988 K100RS 2 valve, no modifications
I purchased the bike as a non runner, but a used alternator fixed that problem (not charging)

My first ride just a few K's was oK

Second ride about 1 hour no problems, but at the end of the ride the fuel pump continued to run when ignition turn off (suspect fuel pump relay) this fixed itself when the bike was started again and then turned off at the key.

Third ride (and last) after about 40 minutes (hot day about 32°C, temperature gauge was just above the middle)  I was in 5th doing about 60kph when I lost power, I pulled over and only had idle, would not rev above 1000 rmp. even after cooling down for 2 hours, still only tickover. the following day (bike was picked up by recover truck) still only tickover.

So far

Fuel pump removed, it pumping fine submerged in a bucket of fuel.
wires in tank have 12v when the starter is pressed.
battery voltage at rest 12.37 (18Ah battery new)
inline fuel filter in tank OK
Hall Effect Sensor checked by pointing heat gun at it with T shaped cover removed, bike was at idle and nothing happened...   

[Cafe racer]

the latest is...
Fuel pump removed, it's pumping fine submerged in a bucket of fuel.
wires in tank have 12v when the starter is pressed.
battery voltage at rest 12.37 (18Ah battery new)
inline fuel filter in tank OK
Hall Effect Sensor checked by pointing heat gun at it with T shaped cover removed, bike was at idle and nothing happened... 
Its running again....and reving as normal
CRC 2-26 to ECU plug and connection to tank for pump and sender
BUT...
when I turned off the ignition the fuel pump continued to run.
So I pulled the relay, popped off its cover and gave it a drink od CRC 2-26
so far all is well, in the next few days I will ride it in a loop around my home, so that it;s in pushing distance if it plays up again. I will update this post in the next few days.

BIG thanks to everyone that helped so far...


 

[The Mighty Gryphon]

Voltage at rest is 12.37.

Should be at least 12.7V.

Your battery is deceased...R.I.P.

[Laitch]

Like the Mighty Gryphon suggests, you need to determine the condition of the moto's battery. If the moto is infrequently ridden and not consistently maintained with a suitable battery charger, it will fail regardless of how new it is.

For cleaning electrical contacts DeoxIT D5 is an effective cleaner. Many riders here use it for cleaning and maintenance of electrical connections. It can be ordered online or can sometimes be found where electronic musical instruments and amps are sold.

[Cafe racer]

Should be at least 12.7V.

Your battery is deceased...R.I.P.

I am not off to the cemetery just yet

12.73 or better   100 percent. Go ride.
12.62   90 percent. Charge it, then go ride.
12.50   80 percent. Charge it, then go ride.
12.32   70 percent. Charge it, then go ride.
12.20   60 percent. Charge it, then go ride.
12.06   50 percent. Charge it, then go ride.

[The Mighty Gryphon]

12.37v resting voltage after a ride tells me that the charging system or the battery has a problem.  Normally it should be 12.8v.

You mentioned earlier that you replaced the alternator.  Alternators don't normally fail unless they are exposed to some sort of external problem.  What you are describing sounds to me like the alternator is not charging the battery while you are riding. 

What is the voltage on the positive battery terminal when the engine is running and the battery light is not lit on the instrument cluster?  It should be around 13.2v or more. 

[Cafe racer]

12.37v resting voltage after a ride tells me that the charging system or the battery has a problem.  Normally it should be 12.8v.

You mentioned earlier that you replaced the alternator.  Alternators don't normally fail unless they are exposed to some sort of external problem.  What you are describing sounds to me like the alternator is not charging the battery while you are riding. 

What is the voltage on the positive battery terminal when the engine is running and the battery light is not lit on the instrument cluster?  It should be around 13.2v or more.

I misunderstood, the voltage I took at rest wasn't after a ride, the battery had been used trying to start the bike.
when I purchased the bike (blind from a trade auction) it had a new battery and new regulator/rectifier but it still failed to charge the battery, hence why it was in a trade auction as a non runner.
I replaced the alternator and it was then charging the battery, I don't recall the exact voltage but something like 13v plus....
sorry for confusion

[Cafe racer]

I have charged the battery off the bike its now fully charged at 13.66v

[Laitch]

Is the moto continuing to run appropriately after the relayotomy?

[Cafe racer]

Is the moto continuing to run appropriately after the relayotomy?

Its running OK ish, previous owner had replaced the pump with a very professional anti vibration damper and gauze filter. the pump is unknown brand and type. on the test run is was vibrating so much against the tank I could not here the engine. So I have ordered a full kit, to replace the professional job.
Is it normal to have a lot of fuel always returning to the tank? due to the heat of the fuel rail, the returning fuel is warm, maybe too warm !!!

Fuel Pump as removed.jpg (84.98 kB . 768x432 - viewed 509 times)
I have ordered this kit

New Kit.JPG (32.24 kB . 502x508 - viewed 462 times)
So now its a waiting game.....
in the meanwhile I will flush out the tank, and rebuild the front brake calipers, just for FUN..

[rbm]

Is it normal to have a lot of fuel always returning to the tank? due to the heat of the fuel rail, the returning fuel is warm, maybe too warm !!!

Yes it is normal. And yes the returning fuel is warm. It can even boil on hot days in stop&go traffic.  Tank gets really warm to the touch and you can consider a fuel cooler (read about them here on this site).

[Cafe racer]

The above fuel pump kit has arrived, so it looks good quality, the vibration damper fits well and the filter a snug fit on the damper. so next job is to clean out the tank and fit it.

[Cafe racer]

Fuel pump installation went kind of ok, took awhile to realise that the securing ring tabs are different widths, and working blind, I had it the wrong way.... so a quick rotate 180° and it popped in with ease.
Started up and runs great, now waiting for inspection....

[The Mighty Gryphon]