/6 wont start when hot

[nhlkats]

R75/6 will start when cold without any trouble. Perfect healthy start without hesitation. But if we ride, the final destination better be back home, because if we turn it off, it won't start up again. The starter won't engage. Hitting the start button just produces a "click". It won't try to turn over, no other sounds, just press the starter button and one single click. Only way to start bike is to wait several hours. Kick start doesnt work. Pop start is not a solution.

So I checked the batt cables. Clean. So is the ground to the back of the trans. So I replaced the oversized sears tractor batt the previous owner had in there with a new sealed Westco for good measure and put a tenderer on too. Didn't help. OK, so its the starter relay, or the starter then, right?

Any suggestions?

http://xs204.xs.to/xs204/06323/bmwbmw_IMG_2704.jpg
My sister's ride

Thanks in advance, gurus.
-Little brother

[Isamemon]

yo sis has a nice ride
what is it with sears tractor batts, my bike came with one too
and all the factory mounting stuff, gone
but yikes, looks like its on a side stand, must not be the factory one

[jdmetzger]

I think you're right on with suspecting the starter relay. It's a lot easier/cheaper to try replacing that first, anyhow. You could get fancy and try running a powered wire directly to the start the next time it happens (taking the relay out of the equation) to see if it turns over. I've never tried it, however.

That is one fine looking bike, btw! :brow

[Braddog]

You already tried what worked for me (I replied to your PM) with the new battery. Check all the connections to the relay and clean them up. Same for the connections under the front cover (diode board, etc). Remember, be sure to pull the ground wire off of the battery before pulling the front cover off.

As mentioned in the previous post, you could use some wire to bypass the relay.

Good Luck, and when you get it fixed, be sure to let us know what it was!

[nhlkats]

you could use some wire to bypass the relay. how does one do this?

give me instructions like im 3, bc i dont know squat about electronics but willing to give it a try if it wont kill me.

[Braddog]

With hints from friends on the RS77 web site that I got when I posted my problem there.

Included is how to use a wire when the failure occurs.

I hope this helps!

[cjack]

how does one do this?

give me instructions like im 3, bc i dont know squat about electronics but willing to give it a try if it wont kill me.

Just put in a new starter relay under the tank. They don't cost much and they do just exactly what your symptoms are.

[nhlkats]

Just put in a new starter relay under the tank. They don't cost much and they do just exactly what your symptoms are.
Im going to try to test some things before assuming and just replacing parts. And anyways, on a complete assumption, $50 + gas for a relay is not cheap for me. Seems pretty expensive for a relay, maybe i can find one somewhere else for a more reasonable price.
http://store.bobsbmw.com/index.asp?PageAction=VIEWPROD&ProdID=2190

[cjack]

Im going to try to test some things before assuming and just replacing parts. And anyways, on a complete assumption, $50 + gas for a relay is not cheap for me. Seems pretty expensive for a relay, maybe i can find one somewhere else for a more reasonable price.
http://store.bobsbmw.com/index.asp?PageAction=VIEWPROD&ProdID=2190

OK. Sorry. I didn't know they had gone up that much. As well, I have seen probably dozens of these go bad just the way yours sounds. I used to carry one in the tool kit. Click and no solenoid sound. The relay socket contacts do get corroded. Hope that is your problem.

[nhlkats]

Click and no solenoid sound. The relay socket contacts do get corroded. Hope that is your problem.hmm, so they make contact when cold but not when hot. maybe give the relay a bath in contact cleaner?


The next thing I would eliminate is the solenoid. Verify that "juice"
is getting to the solenoid when warm.
You could attach an additional 18ga wire to the "start" lead of the
solenoid long enough to reach the + post on the battery. The next time
the problem occurs again, touch the wire to the + post of the battery.
If the starter works; it is not the starter or the solenoid. If it does
not work, then it is either the solenoid or the starter.
Either way it sounds like a cold solder joint somewhere in the circuit.

Couldn't be de diode board because then the battery would be dead and that's
not the problem.
When there's no click or so it must be the solenoid but why does it have a
problem with heat? I should say lift of the cover of the starter engine and
try short cutting the solenoid (direct plus on starter engine, thick cable)
with a warm engine and see what happens. If it starts the solenoid must be
the problem. or you can measure the voltage on the start relais, in en out
poles when starting with a hot engine.

thanks Braddog!

[rocketman]

As someone else mentioned, check the socket that the relay plugs into, I had problems with some of the relays on my /7 and all it turned out to be was the socket it plugged into, NOT the relay itself, spray contact cleaner in the socket and try a fine metal file as well to clean the contacts inside the socket.

Also check that the contacts on the relay are not loose if they are this could be an indication of a short inside the relay. I have used aftermarket relays on some on mine on the /7. They should have a wiring diagram stamped on them, then just match that with something from any car parts store that has the same arrangement of tabs to fit in the socket. Those generally run around 5-10 bux, if I remember right, or used to anyway.

RM

[cjack]

As someone else mentioned, check the socket that the relay plugs into, I had problems with some of the relays on my /7 and all it turned out to be was the socket it plugged into, NOT the relay itself, spray contact cleaner in the socket and try a fine metal file as well to clean the contacts inside the socket.

Also check that the contacts on the relay are not loose if they are this could be an indication of a short inside the relay. I have used aftermarket relays on some on mine on the /7. They should have a wiring diagram stamped on them, then just match that with something from any car parts store that has the same arrangement of tabs to fit in the socket. Those generally run around 5-10 bux, if I remember right, or used to anyway.

RM

Ahhh...I was thinking of the /7 relay too. The /6 relay is a screw on the frame one that looks like the /5 relay but I don't remember if it had the low voltage dropout feature that the /5 relay had. Anyway the /6 relay has spade connectors on the ends of the wires that plug into the relay. While that is still something that has to be clean, it is not the issue that the relay socket on the /7 is.
I don't know what the starter problem is on this bike at this point. The original suggestion about trying to energize the solenoid with a jumper from the battery may be a good way to start the diagnosis...that is to bypass the relay. And go from there.

[nhlkats]

im ready to try the bypass, but am unsure about a couple things.

do i need to remove front cover and diode board? clymers manual says to in order to remove starter. i am not removing starter, but want to know if same still applies for this bypass test?

i picked up some 10 gauge wire. attach one end to starter power lead, then make contact with battery positive (in that order)? anything need to be done with the grounds on the starter or battery?

sure would be nice to have a techy walk me through this. i dont want to screw anything or myself up.

[cjack]

im ready to try the bypass, but am unsure about a couple things.

do i need to remove front cover and diode board? clymers manual says to in order to remove starter. i am not removing starter, but want to know if same still applies for this bypass test?

i picked up some 10 gauge wire. attach one end to starter power lead, then make contact with battery positive (in that order)? anything need to be done with the grounds on the starter or battery?

sure would be nice to have a techy walk me through this. i dont want to screw anything or myself up.

You don't have to remove the front cover...just find the wire on the starter relay that goes to the starter solenoid (it will be black and will have been on terminal #87 on the relay if you can read it), remove it and plug your #10 into it some how. Then touch the other end of the #10 to the battery plus terminal. You will be bypassing the starter relay by doing this. Before you do this you might just try the starter button on the bike and feel if the starter relay is clicking. Then do the test...you can leave the ignition off for the test though.
You are not providing power to the starter motor in this test, but are providing power to the starter solenoid which itself provides the power to the starter motor (instead of the relay doing this job). The current draw in this test will be something like 10 amps or so which is safe to do. There will be a spark at the battery terminal though. Maybe protect your fingers from the contact area at the battery post. The current draw to the starter itself (which the solenoid on the starter provides when it is actuated by this test) will draw as much as 100 amps.

[nhlkats]

You don't have to remove the front cover...just find the wire on the starter relay that goes to the starter solenoid (it will be black and will have been on terminal #87 on the relay if you can read it), remove it and plug your #10 into it some how. Then touch the other end of the #10 to the battery plus terminal. You will be bypassing the starter relay by doing this. Before you do this you might just try the starter button on the bike and feel if the starter relay is clicking. Then do the test...you can leave the ignition off for the test though.
You are not providing power to the starter motor in this test, but are providing power to the starter solenoid which itself provides the power to the starter motor (instead of the relay doing this job). The current draw in this test will be something like 10 amps or so which is safe to do. There will be a spark at the battery terminal though. Maybe protect your fingers from the contact area at the battery post. The current draw to the starter itself (which the solenoid on the starter provides when it is actuated by this test) will draw as much as 100 amps.

Jack,
thanks for the easy to follow instructions.
I tried the relay just before, still clicks.
located #87, plugged in my rigged wire and touched the other end to the battery positive and.... nothing. no sparks, no solenoid action, nothing.
so i double checked that both the battery was functioning and grounded, and that my rigged wire was adequate. they are, and i tried again, nothing.

[cjack]

Jack,
thanks for the easy to follow instructions.
I tried the relay just before, still clicks.
located #87, plugged in my rigged wire and touched the other end to the battery positive and.... nothing. no sparks, no solenoid action, nothing.
so i double checked that both the battery was functioning and grounded, and that my rigged wire was adequate. they are, and i tried again, nothing.

That points to the starter motor. Time to take off the top cover of the engine and have a look. I think there is a big fat red wire going directly to the battery, and a smaller red wire going to the diode board. Also the black wire you just tested goes to the solenoid terminal. You can check the integrity of those connections. Be aware that the red wires are always hot being connected to the battery. You might remove the ground from the battery before you remove the cover, etc. Remove it at the battery rather than the transmission because the less stress on the transmission ground screw threads, the better. If all seems ok, then the next step is to remove the starter motor and you will probably need someone who is familiar with them to figure out what is wrong with it. I'm wondering if the bendix is dry and needs grease, if the solenoid will function. Like the dry parts are not letting the solenoid relax all the way, which may be required to allow the contacts to close and the starter relay to be able to energize it...something like that. Or maybe just dirty contacts. Need for someone who knows the Bosch starter motor to step in here.

[James.A]

I am going to make an observation and a suggestion that I learned my self. There is a nub on the Bosch starter where the solenoid attaches to the motor casing on the terminal end of the solenoid. If you jumper battery+ to this nub, you will have bypassed the solenoid, and a good starter motor will spin during this test. The connection on this nub supplies voltage directly to the brushes of the starter motor. The bike in question starts cold so the tests should be done when the bike is in the failure mode. I would (and in fact have done this) pull the starter cover when the bike is cold and then run it until it is hot enough to reach failure status. You will have to lift the tank to pull the cover and then replace the tank. I'm thinking a short loop to reach full operating temperature and then return home. Then lift the tank while the motor is still hot and try the various by-pass/jumper tests until the problem is isolated. I had to resort to this several years ago when one of my /5's was giving me trouble. On that bike, the problem was that the alternator rotor would go open when heated up and the anti-restart logic loop in the starter relay would disable the starter circuit. Eventualy, the rotor failed completely and the problem became obvious. The /6 starter relay is a different part number from the /5, and I am not sure if it also has the anti-restart function.

Anyway, you must get the bike to mis-behave in order to analyze why it is doing so.

[cjack]

On that bike, the problem was that the alternator rotor would go open when heated up and the anti-restart logic loop in the starter relay would disable the starter circuit. Eventualy, the rotor failed completely and the problem became obvious. The /6 starter relay is a different part number from the /5, and I am not sure if it also has the anti-restart function.

Anyway, you must get the bike to mis-behave in order to analyze why it is doing so.
I think the /6 starter relay while looking the same as a /5 from the outside doesn't have that lockout feature. The schematic indicates that it does not as well.

[pmdave]

Note that the actual starter solenoid is on the starter. The relay under the front left side of the gas tank is the starter protection relay. The protection relays are known to fail, and the relay plug-in sockets are facing up where the contacts collect dirt and corrosion. Simply changing the relay can scrape the contacts clean enough to function, but it's better to use a small screwdriver to scrape the contacts, then grease with Vasoline or other dialectric grease--to keep the metal better protected from corrosion.

Both starter solenoids and starters have been known to fail. Nothing to do with the charging system--assuming the battery is being kept up to voltage.
Testing on the bike by zapping a hot wire from the battery can be harmful--say if you manage to allow the end of the hot wire to contact the engine block. If you're not familiar with such things, I'd suggest removing the starter and sending it off to a rebuilder--either one of the BMW rebuilders, or a local foreign car electrical shop.

If there appears to be a solenoid or starter problem on an old airhead, I'd suggest replacing with a better starter. (see Motorrad Elektric)

pmdave

[tuber1]

geez, I had my /6 hot plenty of times and never failed, but I would have a mechanic check it over. very nice color, that's what mine was...bol d'or red, you don't see many like that; the side stand is factory, if you don't lube it , it will stick and not pop up on you, some ppl like that so they don't fall over, lol

[nhlkats]

it was the starter relay