LM IV starter wiring

[capstan1]

Hi All,

I'm having a problem with my starter motor. I went to start it a couple of days ago and it wouldn't crank so I jumped it and it went fine.

Tested battery - all good
Replaced relay
Checked starter wire and there's juice going to the starter motor when I press the starter switch
Bench tested the starter and it whirs away fine
Removed plugs and rotated wheel in fifth gear and it spins fine by hand

Am scratching my head a bit on this.

I checked the wiring diagram and could not find the loose little sucker that's sticking out in attached image and there's no apparent male attachment. This piggybacks on the lead from the neutral switch. Does it usually go somewhere?

 

[Rafael]

Wouldn't crank, but did the relay click? Solenoid get activated(thunk) ?

It doesn't look like the pig tail is connected to the neutral switch but looks, to me, that the PO added this wire as a jump starter. Hard to be sure from the pic. Actually that's a great idea, I used to use a quarter ($.25).

If it is an extra pig tail on the wire from the starter button, slide back insulator and touch it the the positive terminal on the solenoid connected to the battery. If that works, then the starter button circuit wiring has corroded and developed enough resistance to reduce the amperage enough to not allow the solenoid to do it's job.

My cure for this kind of problem is to shelf the Bosch and buy a Valeo. It's cheaper than having the Bosch rebuilt.

good luck.

 

[OldJock]

Hi Capstan

As Rafael states listening for the appropriate noises can help to diagnose the fault.

First and easiest way to check is to see if the problem lies with either wiring/button/relay or motor/solenoid. To eliminate the relay side touch a screwdriver or the like from heavy connection from the battery to the small spade connection going into the motor. BE SURE NOT TO LET THE DRIVER TOUCH ANYTHING ELSE. Be prepared for a few sparks and the motor springing to life (make sure its in neutral and is secure on a stand or whatever). If the motor turns it over then the fault is probably button/relay related. If nothing or it doesn't turn then its motor/solenoid related.

Most folk send the motor/solenoid off to a shop for repair. Depending on how mean you are it may be a good time to replace the Bosch with a Valeo (lighter uses less current and spins faster). I think John Zibell had another recommendation on a starter that he reckoned was even better, I'm sure he will chime in.

If you get out the wiring diagram you should be able to check the relay by earthing the black wire on terminal 85 or 86 to earth, that's the wire from the start button and that's what pressing it does.

I also agree with Rafael that the spare looks like some sort of POs mod. If its piggybacked off the lead to the Neutral switch then its a pos feed going through the neutral bulb. If you used it as a short to the solenoid I don't think it would work as you would drop voltage through the Neutral bulb. If it was me I'd get rid of it, I don't like live wires floating around ready to blow fuses or worse burn out bits of your loom, not clever but that's just me.

I've attached a diagram made by Kiwi Roy (I hope he doesn't mind, but its so dammed good I'll take a chance). Its not quite identical to your system but pretty dammed close and explains the circuit super clearly IMHO.

John

 

[capstan1]

Thank you gentlemen, much appreciated advice.
I'll check the wiring as per your suggestions tomorrow then buy a Valeo if it's the motor. The Bosch has always struggled on the MK IV. I put a Valeo on my old V50 and was really impressed with it.
Cheers,

 

[capstan1]

Actually just found this diagram when checking out Valeo starters which looks like it could explain that terminal.
Would this act as a way to circumvent the neutral switch?

 

[OldJock]

Hi Capstan

Not quite sure what you're getting at. The Neutral switch on the LM IV does nothing but indicate a green light at the panel to tell you the gearbox is in neutral (or somewhere near neutral). The circuit is a pos wire to the neutral indicator, then goes from the bulb to the gearbox neutral switch. The circuit is held open until in neutral, when a dimple on the selector drum in the gearbox contacts the switch, which is really just a strip of metal. This then completes the circuit to ground current flows and the lamp lights. The neutral switch doesn't hold out the starter like more modern bikes.

The mod you posted up is just using a heavier gauge of wire from relay to solenoid, that would reduce voltage losses and increase the power available to activate the solenoid. Its a good thing to do and has no adverse effects.

If that second wire is piggy backed from the neutral switch I don't think it would do anything. If it was connected to the solenoid it may give you a ground path for the neutral light and it would stay lit. I don't think it would do anything to enhance the power available to the solenoid.

John

 

[Rafael]

Capstan1

The first picture in your last post failed. Is that another picture of the wiring?

Agreed, the Neutral switch is totally unrelated. If the two circuits were connected by the PO then get them back to stock. If that was the case, then the neutral light would have been on all the time.

If your relay has two #87 terminals (not all do) then that could explain the extra terminal but only if it's on the solenoid terminal, as I suspected in my earlier post, not the neutral switch terminal.

The solution put forward on various posts on GT, is to connect a wire directly to the battery to #30 or from another relay powered by a fuse controlled by the key, as I did. This reduces the amperage loss to a minimum compared to having the current flow through the ign. switch. That's where most of the loss usually occurs, not in the wire from the relay to the solenoid, but an extra wire there doesn't hurt as John said.

 

[capstan1]

Hi All,

Many thanks for the feedback. It turns out the starter was a dud. It would spin when off the bike but just didn't have the grunt to spin the motor. I bought a valeo and hey presto.

The little piggyback wire is just an extra lead to the starter spade. Don't know why it's there.

Thanks again for input.

 

[Rafael]

The little piggyback wire is just an extra lead to the starter spade. Don't know why it's there.

This is a first for me- I get to quote myself.

If it is an extra pig tail on the wire from the starter button, slide back insulator and touch it the the positive terminal on the solenoid connected to the battery. If that works, then the starter button circuit wiring has corroded and developed enough resistance to reduce the amperage enough to not allow the solenoid to do it's job.

It's an emergency jumper. Better than a quarter ($.25). When the starter circuit fails this becomes your starter button - assuming the battery is charged and has not failed. Turn bike on - pull back insulator - tough it to the big positive post on the solenoid and bam! you have ignition.

 

[capstan1]

Now that's handy! Thanks mate.