Hey folks. Brand new. Great forum lots of good stuff. I am also hoping for parts, but that will be another post.

Okay. 1987 K100RS. One owner, me. 160k klicks on it. Here is the problem. On a cold start (the bike has sat for say more than 9 hours), i get about 5 minutes of riding then it stalls. Wait a minute or two, start up and go. No more stalling. Can ride all day and nothing. My mechanic has nothing. He is fearful it is the hall sensor, but to order one here is $800 bucks. I see they are cheaper on line but would really like some hints advice before we needlessly replace a part. He has re brushed the starter (it started to fail), re brushed the alternator and cleaned all electrical. Replaced fuel filter. (as a side note lubed the clutch cable...wow!!). I am running on one tank with fuel injector cleaner, will use up the bottle and see if that makes a diff.

Now if this helps, if i try to run hard on a cold start up, doing 50 clicks an hour right away, it still stalls but stalls hard. If i go real slow (no more than 20), i can ususally baby it as it is about to stall and save it. (Or coast a bit then bump it).

Thank you all (now to poke around)
Craig.

Remove the cover from you HALL sensors, and start the bike.
Use you wife's hair dryer and warm up the hall sensors. If the engine stops when they are hot you pin pointed the problem. (I believe your mechanics may be right).
The good news is that you don't have to buy the sensors from BMW. Check the internet for HONEYWELL S&C - 2AV54.
Check my page on EFI to troubleshoot them

Update. Great help Crazy Frog. i got the hall sensors. 20$ a piece. Took them to my mechanic. He installed them no problem. But - bike stalls after about the same length of time, basically no diff. Any other ideas? He did add the when the bike stalls, the fuel pump keeps going, hence it floods the engine, making the re-start very difficult. Next step for me is to take it to the local BMW dealer here and see if the can hook it up to their computers and see something. Bummer. (insert sad face here!)

Nyssa wrote:Update.
(insert sad face here!)

Hi Nyssa,
Have you checked the connection to the EFI controller for bad connections? These need treatment with DeoxIT after 20 plus years. What resistance value are you getting on the wire from the water temperature sensor if you have a fluctuating bad connection that will cause all sorts of running and stating problems.

Thinking as I type about what the mechanic said, how does the fuel pump keeping running for a few seconds after a stall flood the engine? That will not flood the engine unless the injectors are still getting injection pulses from the EFI controller or they are leaking.

That comment of his sounds very strange and frankly sounds to me like he is actually saying "I have no idea but I will throw out something technical sounding to fool the punter into thinking I know what I am doing and he should pay me to throw parts at it till the problem is fixed", sorry a bit grumpy this morning.
Regards,
K-BIKE

Does the ignition lights come on when it stalls?
I only ask as i had this problem too, when it stalls turn the ignition off and on quickly as your still moving, it proberbly will carry on running or quickly restart it (you might need to do it twice)

If it does carry on running or after you press the start button it starts its the ignition.

I took the ignition apart and cleaned all the terminals and its been perfect since.

Mine was like yours, always did it not long after i started the bike then would be ok the rest of the ride.

So here we are now over a month later and my bike is back. $2000 later the dealer: Replaced fuel pump. Pressure Regulator. Relay. Sensor for the water temp. Rebuilt the water pump. It looks like the stalling issue was a failing fuel pump and had nothing to do with the hall sensors. Thank you everyone for your help. I will stick around this place and now i am going to start looking for parts again for my aging K100. The stuff i didn't understand was all about the number of pressure bars the fuel pump was doing, guess it was about 2.5 bars short, plus as soon as the bike got turned off, it stopped, apparently it is supposed to keep going for a few minutes?? Whatever, bike runs awesome. I even spent $40 on two new tank decals. Ace!

I love it when mechanics throw parts at a problem instead of troubleshooting.

Nyssa,
Sounds as though K-Bike got it right. You had no need to run to the dealer,
it would have been solved here. You have paid for parts you didn't need.
He will be looking for you again. Obviously money is no object.
Dear o dear.
Ajays.
Really good sound well kept 87 K100rs's are going for that price here in the UK.
I have just bought another K75s in top condition for £800.

Ajay, glad you're back into the bricks again...

club_c,
Never left them, K100 (2) were getting a bit too heavy for me.
I retained my K75's (2) now 3. They being lighter are just about right.
Then there is my 3 wheeler Gilera 500 for when I get old...!
Cheers Ajays

ahhh. Thought you were brickless for a bit when I said you'd sold the k100's. Thought I was bad with an R and a K. Bet your family just smiles and rolls their eyes...

I guess the 3 wheeler Gilera is still in the crate and you are not quite ready for it

Come ride with me.....not ready for the Gilera....yet Bert.

The date is wrong, it was this year in the spring. The grunt is normal for people of my vintage.
Ajays

Hi Nyssa,
The fuel pump should stop the moment you turn off the ignition switch. The pressure should be maintained but that is because the regulator does not leak the fuel lines don't leak and the injectors don't dribble. Assuming all of those things the pressure remains present in the fuel injection side. Partly that is intended so as to help reduce the risk of the fuel boiling and giving the system a vapour lock also it means the pressure is there the moment you go to start and the pump does not need to build up pressure. I am really pleased it is back to running as it should!
Regards,
K-BIKE

@ Ajays - what did you use for camera? Just done a weeks riding in the highlands and could have done with one!

Bert is correct, Maplin special offer is £10 less now £49.95.
Go here and get one for £9.95. Post Free..!
http://www.buyincoins.com/Camera/Mini-Camcorders/
Renez
I find that the keyring cameras are easier to use and just as efficient.
Go get one.

Good one, i'll give that a go. Thanks!