Ran fine, now won't start.

[mblackwood]

Greetings Gents-

So... it's a 1993 R100R

just flipped 50k on the odometer.
originally purchased in '93 by my father, and very very generously given to me on my 30th Birthday almost 6 years ago with 17k on the odo.

Now for the trouble:
bike had been daily driver for about 6 months. kept it tuned, ran great, no problems.

one day, at lunch, i'm returning to work and the bike is still running just fine.

i stop at the local quicky mart to get some water (it was a hot day) and when i return to my bike, it won't start.

not only will it not start, but the Tachometer does a really bizarre thing and starts climbing up to the 5k range. (NOTE: the engine is NOT running when this is happening.)

The start doesn't turn over. yes, it's a valeo. yes it was replaced about a year ago because it sounded something like a rat being squeezed when it was being used)

there's a weird humming noise coming from underneath the gas tank.

the headlight seems to be bright and glowing properly, so i know that the battery isn't dead.

since then, I've done the following trouble shooting:

1) made sure battery was charged fully (and maintained a charge over several days) (it was replaced in 07/07)

2) spot checked all connections (with tank off) and they all looked very great- clean.

3) checked which relay was buzzing- it's part number: 61311459677
(located near the rear (crotch end) of the gas tank, if you're sitting on it.)

4) i've swapped the relay out with a new one- still buzzing.

5) these parts have been swapped out in the past year and a half (sub 6k miles on them: diode board, voltage regulator, alternator stator & brushes)


so..... I'm out of ideas.

do you any ideas?

what i haven't checked:

ignition control unit
electronic

[20774]

According to this site http://www.airheads.org/content/view/159/98/ that is a "load shedding" relay. Not sure of its function, but it obviously didn't solve the problem.

My guess is that it's your starter relay...corrosion on the contacts or maybe the internal relay just won't latch. Something like 61 36 1 389 105 would be my guess. You could try and pull the current one out of its socket and replug a few times to scrap some of the corrosion off.

[Boxerkuh]

It sounds electrical to me. Sounds like a bad ground. You have to remember that your bike is 15 years old and wires do wear. My problems last year began just like yours, replaced relays, but I was not able to solve it until I replaced the main wiring harness. All you need is one break or one wear point (which you will never find in the main harness) and it will drive you crazy. Good luck. I had to wait on mine from Germany. My food for thought anyway...:eat :drink

[mblackwood]

According to this site http://www.airheads.org/content/view/159/98/ that is a "load shedding" relay. Not sure of its function, but it obviously didn't solve the problem.

My guess is that it's your starter relay...corrosion on the contacts or maybe the internal relay just won't latch. Something like 61 36 1 389 105 would be my guess. You could try and pull the current one out of its socket and replug a few times to scrap some of the corrosion off.

Thanks for the thoughts on that.
I've gone over each of the contacts- they're all shiny clean- almost brand new looking.

i'll check them all again though... measure twice, cut once and all that goodness.

thanks again

[mblackwood]

It sounds electrical to me. Sounds like a bad ground. You have to remember that your bike is 15 years old and wires do wear. My problems last year began just like yours, replaced relays, but I was not able to solve it until I replaced the main wiring harness. All you need is one break or one wear point (which you will never find in the main harness) and it will drive you crazy. Good luck. I had to wait on mine from Germany. My food for thought anyway...:eat :drink

sadly- i'm afraid that this *might* be the case.

I do remember that my father replaced the harness about 3 years before he gave it to me- due to it shorting out, but... he doesn't seem to remember what his mechanic (blasphemer for paying someone to work on that bike! :burnout ) said that the problem was outside of the replacement harness....

I'll check that though...

[James.A]

Not certain if it would apply to your bike, but, an open alt. rotor will disable the starter on an early 70's airhead. It's pretty easy to test for.

[20774]

Not certain if it would apply to your bike, but, an open alt. rotor will disable the starter on an early 70's airhead. It's pretty easy to test for.

:scratch News to me...the alternator is part of the charging system, separate from the ignition system. Can you provide some more details?

[James.A]

Sure thing Kurt.

On my /5's, the starter relay has what is described as an analog logic circuit incorporated. The device detects alternator output as an indication that the motor is turning. The relay will not direct battery voltage to the starter solenoid if motor is spinning as indicated by the alternator. For reasons that I do not fully understand, the absence of continuity thru the rotor causes the relay to invoke the logic circuit to act to disable the starter button. It has happened twice on my/5's, the last time being a few months back.

[20774]

James -

I'm not sure I'd heard that before, but I did some digging and read the ChiTech electrical manual and it describes it as you outline. It didn't mention the starter relay specifically, but describes a "Repeat Start Prevention Relay" or sometimes called the "Starter Lockout Relay". Those descriptions suggest its own relay rather than being bottled up inside the starter relay of the /6 and later bikes. However, my Haynes shows the starter relay with an extra component inside, likely the circuit you mention.

The ChiTech manual says that for the /6-on bikes, this lockout feature was not present thus the charging system doesn't play a roll in the starting circuit like the /5 bikes. I guess on the the /6-on bikes, the clutch switch and/or neutral switch are part of the design to keep the starter from being engaged while in gear and clutch engaged.

[Polarbear]

Try this, as sometimes the simple things should be checked first:). I have seen TOO many batteries, with dead shorts in them, to dig into my bike until a battery load test is performed. LOAD the battery to see if its shorting out inside! Any auto parts store can do this, OR, you can by "jumping" the bike battery. If it starts with a jump, you have solved the problem. A bad battery. No matter how new the battery is, they can fail. YOU can jump your battery to a car battery, without any issues, using care to not ground the cables on the frame! Even bike shops(many) sell biker jump cables, if you need to find them. Standard cables will work, with care given....Randy:thumb :usa

[PGlaves]

It sounds like a failing ignition pickup (crankshaft position sensor). To me the strong clue is the tach action. It sounds like frequent erroneous TDC signals coming from the sensor - causing frequent signals to the coil. The plugs might or might not fire randomly, and if they do it might be a weak and erratic spark due to lack of dwell time.

[James.A]

Trying a jump start is a great idea! I like the load test idea also. My factory service manual includes directions to do a load test on the bike. Maybe that is not included in Chiltons or Haynes or Clymers.

It's a good thing that PaulG jumped in here to knock our heads together. That electronic tach thing is something I know nothing about. Would the ignition pick-up/crankshaft position sensor drop the electric start function? It seems reasonable to me that a device like that might be employed to prevent engaging the starter while the motor is running.

If the bike will not roll the starter with a jumper battery, would it be reasonable to try to roll the starter by directly energizing the starter using a jumper wire between the battery+ and the small spade connector on the solenoid?

I'm wondering how mblackwood got the bike home, push start?, trailer?. As I read it, the electric start would not engage.

[PGlaves]

T

It's a good thing that PaulG jumped in here to knock our heads together. That electronic tach thing is something I know nothing about. Would the ignition pick-up/crankshaft position sensor drop the electric start function? It seems reasonable to me that a device like that might be employed to prevent engaging the starter while the motor is running.



I think it does - BUT - I'm not sure. Never had to troubleshoot that defect on an Airhead. But the squirrly tach symptom is a dead givaway for a shot sensor or sensor wiring on the Oilheads.

[Boxerkuh]

I was worried about my Odyessy Gel battery at one point, after 3 years in the bike and reading that they sometime fail all of a sudden, without warning. I took the battery out and took it to Auto Zone and had it bench tested 3 times in a row. It showed 380 cranking amps on the third crank with no rest and a load on it each time. I did not know what that meant so I emailed Odyessy and they informed that anything greater than 220 cranking amps is great and not to worry. I re-installed the battery and it has been in the bike ever since. Hope that helps a little bit...

[mblackwood]

Try this, as sometimes the simple things should be checked first:). I have seen TOO many batteries, with dead shorts in them, to dig into my bike until a battery load test is performed. LOAD the battery to see if its shorting out inside! Any auto parts store can do this, OR, you can by "jumping" the bike battery. If it starts with a jump, you have solved the problem. A bad battery. No matter how new the battery is, they can fail. YOU can jump your battery to a car battery, without any issues, using care to not ground the cables on the frame! Even bike shops(many) sell biker jump cables, if you need to find them. Standard cables will work, with care given....Randy:thumb :usa

Hey there-

Finally found a little bit of spare time to get back to this.

I appreciate the suggestion and, sadly, after taking the battery to the local parts store, wasn't the cause.

thanks for replying though!
on to the next testing..... :doh

[mblackwood]

Try this, as sometimes the simple things should be checked first:). I have seen TOO many batteries, with dead shorts in them, to dig into my bike until a battery load test is performed. LOAD the battery to see if its shorting out inside! Any auto parts store can do this, OR, you can by "jumping" the bike battery. If it starts with a jump, you have solved the problem. A bad battery. No matter how new the battery is, they can fail. YOU can jump your battery to a car battery, without any issues, using care to not ground the cables on the frame! Even bike shops(many) sell biker jump cables, if you need to find them. Standard cables will work, with care given....Randy:thumb :usa

Thanks for the thoughts.

tried checking the battery at the local auto supply store with their battery toy. seems like it was not the battery since it holds a charge, and has well over 220 amps after a load test. not sure how they did the load test, but the batery seems to hold voltage (even after sitting for the past few months) just fine. so... bad electrolyte or none, that's kinda something for me to feel comfortable with.


however, the insight is and was valuable- so again, I thank you.

[mblackwood]

Try this, as sometimes the simple things should be checked first:). I have seen TOO many batteries, with dead shorts in them, to dig into my bike until a battery load test is performed. LOAD the battery to see if its shorting out inside! Any auto parts store can do this, OR, you can by "jumping" the bike battery. If it starts with a jump, you have solved the problem. A bad battery. No matter how new the battery is, they can fail. YOU can jump your battery to a car battery, without any issues, using care to not ground the cables on the frame! Even bike shops(many) sell biker jump cables, if you need to find them. Standard cables will work, with care given....Randy:thumb :usa

Trying a jump start is a great idea! I like the load test idea also. My factory service manual includes directions to do a load test on the bike. Maybe that is not included in Chiltons or Haynes or Clymers.

It's a good thing that PaulG jumped in here to knock our heads together. That electronic tach thing is something I know nothing about. Would the ignition pick-up/crankshaft position sensor drop the electric start function? It seems reasonable to me that a device like that might be employed to prevent engaging the starter while the motor is running.

If the bike will not roll the starter with a jumper battery, would it be reasonable to try to roll the starter by directly energizing the starter using a jumper wire between the battery+ and the small spade connector on the solenoid?

I'm wondering how mblackwood got the bike home, push start?, trailer?. As I read it, the electric start would not engage.

You are correct- the electric starter wouldn't engage.
In fact, I couldn't even PUSH START the bike.

As of today's date, the bike is still dead. Since the weather is getting nice around here, and I'm looking at getting the bike started again, I'll try to finish up the post with what I find the problem to be.

The reality at present, however, is that I've taken the camshaft position sensor (part number 12111244088) out of the bike and had it tested- came up clean and ready to rock and roll.

I've also taken out the ignition control and had the fellas at BMW test it for me since clymer's says that's what one is supposed to do... (that was part number 12142325284)

so... now i am going to check the ignition switch, do a load test on the bike itself, and hope that it's just a bad ground that I've over looked while ripping apart the wiring harness (again) and re-testing each and every wire on it at each end (which, sadly, i made time for at one point a few months back... it took 2 full 6 hour days... and I don't recommend it)

more to come....

... oh, and I got the bike home by pushing, trucking and putting it in to a van (at one point).

now it rests comfortably in my garage... taking up space, instead of being ridden.

[RecycledRS]

Have you determined why the relay (load shedding relay) is buzzing? I suspect you may find there is a short in the wiring harness somewhere causing this relay to buzz. It is also possible that the electrical frequency created by the relay buzzing is being picked up (induced through wiring) by the Ignition Control Unit (ICU) and sending an output signal to the tach. Since the ICU senses the ignition is active it will not allow the starter circuit to operate. Trace through the wiring harness for any obvious chaffing or damage. Its only a theory.

[Rod Sheridan]

:scratch News to me...the alternator is part of the charging system, separate from the ignition system. Can you provide some more details?

The design idea is to prevent the ham handed from engaging the starter motor while the engine is running.

So, the ground return path for the starter relay is through the alternator rotor, because if the engine isn't spinning, the rotor voltage will be almost zero (Only the field flashing lamp will be providing excitation power to the rotor).

So, if the rotor or brushes go open, the strater relay coil current has no return path to ground and the bike won't start.

One of those neat little things that make airheads special, although I don't know if your model incorporates this feature........Rod.

[mblackwood]

The design idea is to prevent the ham handed from engaging the starter motor while the engine is running.

So, the ground return path for the starter relay is through the alternator rotor, because if the engine isn't spinning, the rotor voltage will be almost zero (Only the field flashing lamp will be providing excitation power to the rotor).

So, if the rotor or brushes go open, the strater relay coil current has no return path to ground and the bike won't start.

One of those neat little things that make airheads special, although I don't know if your model incorporates this feature........Rod.

Thanks Rod!

I'll quadruple check the rotor and make sure all is sound there. hopefully (crosses fingers) something will show up, and I'll have this otherwise fine airhead on the road again, soon enough!

[boxermaf]

I don't think that this circuit function exists on the later bikes (to prevent a "re-start" attempt of the engine while it is already running) it is very possible to try to to "restart" a perfectly working, post 1980 airhead - I haven't done it myself, but I know of several who have been rewarded by the scream of the bendix... a horrible sound, for sure.

[Hodag]

what ever happened?

i have the same tach issue/no go on my rs??