Abandon Starter Relay! (?)

[TrueAce]

Thanks, Martin, good tip. I'm headed to the Autozone store this afternoon to see what they got.

[escodsm]

Hey Robert & all - (Robert I have an ongoing thread over at K100-Forums that you have helped me with)

I am still unable to get my K75 running with the start button.  The starter works great if I slap 12v to it right from the battery.

So, in reading this thread which I found very interesting - - I could essentially start the bike by merely juicing the starter itself?  NOT to ride - as the bike is unfinished - I just want to start the ol' girl!  The methods you guys are talking about is basically to skip the starter relay altogether, and go direct to the starter with a bounce switch like they have in race cars....so why couldn't I just hook up 12v to the starter nut and fire the bike up this way?  Once it starts, I just let go of the jumper to the starter nut and thats it.

I also read online about splicing a ground to the frame, from the "starter relay control side ground" - - anyone know what terminal that is on the stock relay?  Thanks everyone!

[Martin]

I've had my relay stick twice but never had the contacts weld them selves closed. Maybe I was just lucky, but it annoyed me enough to fit a battery isolator switch in the earth cable.
Regards Martin

[rbm]

So, in reading this thread which I found very interesting - - I could essentially start the bike by merely juicing the starter itself? 

Yes, you could.  This thread talked more about finding a way to bypass the starter relay to eliminate a known weakness in the K-bike electrics.

NOT to ride - as the bike is unfinished - I just want to start the ol' girl!  The methods you guys are talking about is basically to skip the starter relay altogether, and go direct to the starter with a bounce switch like they have in race cars....so why couldn't I just hook up 12v to the starter nut and fire the bike up this way?  Once it starts, I just let go of the jumper to the starter nut and thats it.

That is possible.  I'd use a battery isolation switch to do the switching rather than freehanding a bare wire, just because of the current that will get drawn as the start motor runs under load.

I also read online about splicing a ground to the frame, from the "starter relay control side ground" - - anyone know what terminal that is on the stock relay?  Thanks everyone!

You'd be looking for the Brown/Green wire on the two-pole white AMP connector that attaches to the relay coil.  I'm not sure if this splice would hurt the ICU or not so, if you actually carry it out, I'd isolate the Brown/Green wire first and insert your own wire to ground.  Remember that you'll not have any safety mechanism to prevent you from engaging the start relay even with the engine running whenever you hit the start switch.

[escodsm]

Robert, sorry but I do not have a brown/green wire anywhere near the starter relay. 

http://www.motobrick.com/ducktech/kwiring/Early%20K75%20K100/K100_Early_Wiring_Diagram.jpeg

Perhaps you mean on a K100? Mine's a K75.  If you could isolate the exact wire on the above diagram, that would be chipper!!!

Happy holidays to all.

[rbm]

Sorry, I was writing from memory; obviously my memory is quite fallible. Should have referenced a schematic.   It's Brown/Red.

[escodsm]

 :clap:
Successfully grounded out the HES brown/red wire at the starter relay.

Bike is turning like a champ, but won't start. Plugs sparking, exhaust (no muffler yet) is getting fuel in it.


New strange behaviors....Will turn with bike in gear, or at least try to. Pulling in the clutch doesn't make a difference. 

Thoughts...bad gas is a definite.  I need to get fresh gas in there.
Plugs look okay but could be old, also couldn't hurt.

[TimTyler]

Here is an idea, replace the BMW relay with a real starter solenoid.
http://www.autozone.com/batteries-starting-and-charging/solenoid/duralast-solenoid/82182_0_0/?checkfit=true

I'd like to try this.

Looking at this one http://www.colehersee.com/home/item/cat/187/24047/  They make a "marine" version of that too, maybe for mounting outside the relay box?

[Scott_]

Bike is turning like a champ, but won't start. Plugs sparking, exhaust (no muffler yet) is getting fuel in it.

Re the no start, I'd double check that the plug wires are correctly installed. This has tripped up more than one in a 'no start' condition after some repair work

[The Mighty Gryphon]

Tim,

Looking at the schematic of the bike, it looks like the starter relay is powered from the ignition control unit.  I don't know what the current capacity of the ICU is, but I believe there are schematics of it's inner workings that may give an indication of what it can deliver.  This current from the ICU is probably the determining factor on what relay can be used. 

One option might be to use a heavier Bosch relay.  I have stumbled across a 100 amp(vs the K bike 75A) that is a direct replacement.  The price also looks pretty good at $29.97 from this place:

http://theelectricaldepot.com/relays/high-power-relays/power-relay-12v-spst-100-amps-br-1-each

Another option is to use a starter relay from a big v-twin rice burner.  I have seen a number of relays on Amazon in the $10-12 range for bikes like the 1700cc Suzuki Boulevard that might work in our bikes with a few mounting modifications. 

I'm thinking the key thing about a starter relay for our bikes is that with all the electronics this relay should have good suppression across the coil.  For this reason, I think I am revising my suggestion for an automotive or marine solenoid.  I don't feel comfortable with the suppression you would get with these devices, especially since seeing how the coil is connected to the ICU.

[TimTyler]

One option might be to use a heavier Bosch relay.  I have stumbled across a 100 amp(vs the K bike 75A) that is a direct replacement.

The amp ratings for both those relays looks the same to me: Resistive load Switching current/no. of operations   A/Thousand      75 /≥ 125
0 332 002 150  vs  0 332 002 161

150 has "twin contacts" and 161 has "single contact"

[rbm]

I'm thinking the key thing about a starter relay for our bikes is that with all the electronics this relay should have good suppression across the coil.  For this reason, I think I am revising my suggestion for an automotive or marine solenoid.  I don't feel comfortable with the suppression you would get with these devices, especially since seeing how the coil is connected to the ICU.

The starter relay draws 350 mA from the ICU to engage.  This small current draw is not much and is easily handled by the ICU's transistor output stage.

The key factor in reliable operation of the starter relay is not so much suppression of back-EMF in the coil, rather it's having good hysteresis (i.e. a marked difference between the pull-in voltage and the drop-out voltage).  The relay will oscillate around its pull-in/drop-out voltage if the two are too close together in value, causing the contact welding we see.  Bosch designed a 12V starter relay that uses a 6V coil and electronics that introduce hysteresis. This starter relay will pull-in close to 12V but hold even if the battery terminal voltage drops to 10V (typical for a worn battery) once the engine starts cranking.

[TimTyler]

....  Bosch designed a 12V starter relay that uses a 6V coil and electronics that introduce hysteresis.

Thanks, Robert. Is that the 0 332 002 161 OEM relay?

[F14CRAZY]

Here is an idea, replace the BMW relay with a real starter solenoid.
http://www.autozone.com/batteries-starting-and-charging/solenoid/duralast-solenoid/82182_0_0/?checkfit=true

I'd like to try this.

Looking at this one http://www.colehersee.com/home/item/cat/187/24047/  They make a "marine" version of that too, maybe for mounting outside the relay box?

yeah I was thinking of just like a generic old Ford starter solenoid. Least if it went bad on the road you could get one at any auto parts store or salvage yard. Hell with those Fords you can just put a screwdriver across them

[The Mighty Gryphon]

F14, The problem with automotive relays is that their coils draw about 3 amps.  As Rob points out, the Bosch relay coils only draw 0.35 amps. 

It might be possible to drive an automotive relay with a small relay which is driven from the ICU.  This would allow higher current handling contacts to be driven by the low power output of the ICU. 

Rob, Hold-in on the automotive starter relays is usually somewhere in the range of 5-6 volts, so drop out shouldn't be an issue.  As far as the rating of the 161 relay, the model designation is for 100 amps vs. the designation of 75 amps for the K relays.  I would have to think that the difference would relate to an ability to handle higher currents that may not show in the specs. 

I haven't researched them, but there are a few Suzuki and Yamaha relays that look like they may be good replacements for the Bosch units.  What has caught my eye with them is their price which is in the $10 range.  Perhaps the coil current is low enough on these relays that they could be wired directly to the start button avoiding the ICU.  Unfortunately, there are no readily available specs for any of these relays, and I don't have the time right now to look for them.

[F14CRAZY]

F14, The problem with automotive relays is that their coils draw about 3 amps.  As Rob points out, the Bosch relay coils only draw 0.35 amps. 

It might be possible to drive an automotive relay with a small relay which is driven from the ICU.  This would allow higher current handling contacts to be driven by the low power output of the ICU. 

It may seem counterproductive but can you drive an automotive relay with the stock relay? The stock relay should last forever in that case

[TimTyler]

It may seem counterproductive but can you drive an automotive relay with the stock relay? The stock relay should last forever in that case

I was thinking this too. Although since my stock relay has been arc'd and welded a couple of times, it might make more sense to swap it out with a cheap, low amp relay.

I was also thinking, regarding the original post, that if one did just hardwire a switch to the starter (bypassing the starter circuit and relay) wouldn't the rider need to depress the handlebar starter switch AND the new starter switch to get the bike going? The old starter circuit still needs to activate the fuel pump and other stuff, right?

[The Mighty Gryphon]

You're right, it looks like the start button signal is routed through the ICU to energize the start relay.  I like the idea of having the original relay energize the external one.  Saves the contacts and isolates the inductive kick from the external relay.

[F14CRAZY]

Do the factory style relays go bad often enough? I have at least 30k worth of starts on mine and no issues yet

[rbm]

Thanks, Robert. Is that the 0 332 002 161 OEM relay?

I can't say for sure.  I remember picking up this tidbit of info during my forum reading.  The info came from BMW Service Bulletin 12 001 01 (023).

[TimTyler]

I had two relays in 60k miles and they have stuck maybe 20 times, probably more. I've tried everything I could except new starter motor bearings, and i just ordered those.

[F14CRAZY]

I had two relays in 60k miles and they have stuck maybe 20 times, probably more. I've tried everything I could except new starter motor bearings, and i just ordered those.

Haven't had one stick yet. My previous battery was weak for a while and it ran out of juice and stopped turning the starter but no stuck relay  :dunno

I should check on my relay though. Knowing that this was owned by Drake I have little doubt that it's not OEM

[TimTyler]

This Honda PDF has a lot of info on relays and relay terminology.

[Inge K.]

You're right, it looks like the start button signal is routed through the ICU to energize the start relay.

The power from the start button goes directly to the relay coil, and the relay coil is grounded by the ignition
ECU as long the rpm is lower than 711.
About the starter relay reliability......my oldest K have past 200K km, never had any problem with the relay.

[TimTyler]

Do you guys have ground wires connected to your starter motor mounting screws? I don't.