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Discussion Starter · #21 ·
Update:

Since I'm waiting for a new switch which is on backorder from the manufacturer I reassembled mine, did the continuity test and everything tested fine. And in the process I lost the springs that caused the switch to return to the run position which was causing the engine to die so I put it back together and started it and was able to have it run as the switch was not returning. But if I attempted to drive it that way, letting the clutch out while in gear killed it. I'm assuming because the starter motor was running continuously. But I did notice another symptom, there's a high pitch whine, an electrical type of whine, coming from under the tank. Is that off the actual starter solenoid do you think? This starts as soon as I turn the ignition to the on position and continues regardless of the position of the starter / kill switch...

Any help in this matter would be greatly appreciated thanks!

Also I have a video but can't figure out how to post it..
Let's see if this works...
 

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Since I'm waiting for a new switch which is on backorder from the manufacturer I reassembled mine, did the continuity test and everything tested fine.
You get continuity across the red/white and red/black wires when the switch is in the Run position?
If you're confident you did the tests right, then the switch is okay and there's no sense in getting a replacement.

The only other thing I can think of is something happened inside the main relay (#21 on the schematic). You said you had the bike on a tender and the battery got smoked - I guess it's possible this could have fried something in the relay to cause the bike to run only when the starter's engaged, I just can't figure out what exactly. Maybe Psyco can.
Anyway, this relay is used on a whole bunch of different Yamahas so if you can pull one from another bike you can test it that way.


But if I attempted to drive it that way, letting the clutch out while in gear killed it. I'm assuming because the starter motor was running continuously.
Yeah don't ride the bike with the starter constantly running, lol.

But I did notice another symptom, there's a high pitch whine, an electrical type of whine, coming from under the tank. Is that off the actual starter solenoid do you think? This starts as soon as I turn the ignition to the on position and continues regardless of the position of the starter / kill switch...
I saw the vid, that whine is normal, it's the throttle servo.
 

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Discussion Starter · #23 ·
You get continuity across the red/white and red/black wires when the switch is in the Run position?
If you're confident you did the tests right, then the switch is okay and there's no sense in getting a replacement.

The only other thing I can think of is something happened inside the main relay (#21 on the schematic). You said you had the bike on a tender and the battery got smoked - I guess it's possible this could have fried something in the relay to cause the bike to run only when the starter's engaged, I just can't figure out what exactly. Maybe Psyco can.
Anyway, this relay is used on a whole bunch of different Yamahas so if you can pull one from another bike you can test it that way.




Yeah don't ride the bike with the starter constantly running, lol.



I saw the vid, that whine is normal, it's the throttle servo.
That being said the wine increases when I do things like all the passing indicator brights etc
 

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Discussion Starter · #24 ·
You get continuity across the red/white and red/black wires when the switch is in the Run position?
If you're confident you did the tests right, then the switch is okay and there's no sense in getting a replacement.
Yes continuity was just fine in the off position there is no audible indicator but it was on in the run and start positions
 

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Discussion Starter · #25 ·
The only other thing I can think of is something happened inside the main relay (#21 on the schematic). You said you had the bike on a tender and the battery got smoked - I guess it's possible this could have fried something in the relay to cause the bike to run only when the starter's engaged
Well will I have the whole harness basically taken apart again I was testing some continuity in different parts of the harness and I noticed when I took the micro relay apart I couldn't get continuity across some of the connections and there was a two prong relay that also had no continuity acrossed it I don't know if you can test relays in that way if I was even doing it correctly but yeah I imagine getting some of those multifunction relays and replacing them might be the next step but yeah I had already ordered the switch I'm currently in Phoenix kind of stranded I was driving out here in the work truck to resolve the issue with the bike was possibly going to sell it now my truck's broke down the bike won't run and my mother insisted on ordering a switch for me LOL you know I was trying to get her to hold off it just happened to be the part I was diagnosing at the time she took it upon herself to pay for it hahaha
 

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Well will I have the whole harness basically taken apart again I was testing some continuity in different parts of the harness and I noticed when I took the micro relay apart I couldn't get continuity across some of the connections and there was a two prong relay that also had no continuity acrossed it I don't know if you can test relays in that way if I was even doing it correctly but yeah I imagine getting some of those multifunction relays and replacing them might be the next step but yeah I had already ordered the switch I'm currently in Phoenix kind of stranded I was driving out here in the work truck to resolve the issue with the bike was possibly going to sell it now my truck's broke down the bike won't run and my mother insisted on ordering a switch for me LOL you know I was trying to get her to hold off it just happened to be the part I was diagnosing at the time she took it upon herself to pay for it hahaha
There are a bunch of relays in the tail section, just focus on the main relay (Yamaha calls this the 'relay unit' in the service manual) at least for now since that's the one that controls the bike's running and starting logic.
The relay if I remember correctly is labeled with the part number in yellow - 5VK-81950-40 (maybe -41). Disconnect it and do the continuity tests described on page 8-99 of the service manual. These are testing the diodes inside, so make sure you insert the red and black leads of your meter into the relay exactly the way the SM says. Notice you'll be testing each connection for continuity one way, then reversing the leads and testing in the other direction.

Any of the tests fail, replace the relay.
 

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Discussion Starter · #27 ·
There are a bunch of relays in the tail section, just focus on the main relay (Yamaha calls this the 'relay unit' in the service manual) at least for now since that's the one that controls the bike's running and starting logic.
The relay if I remember correctly is labeled with the part number in yellow - 5VK-81950-40 (maybe -41). Disconnect it and do the continuity tests described on page 8-99 of the service manual. These are testing the diodes inside, so make sure you insert the red and black leads of your meter into the relay exactly the way the SM says. You'll be testing each connection for continuity one way, then reversing the leads and testing n the other direction, because diodes are only supposed to pass current in one direction only.

Any of the tests fail, replace the relay.
Thank You, good direction to point me in this morning. I appreciate all the help, I'm sure you guys know I do. I'll post if I finally hunt down my issue... I'm hoping I have the correct SM or I'll be hunting that down too 🤣
 

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P.S. One thing I hadn't thought of until just now - if the relay fails every single one of the diode continuity tests (failing meaning there's continuity when there shouldn't be, and no continuity when there should be), then the relay is good. This just means that your multimeter is providing the source voltage for resistance/continuity opposite to the way the Yamaha meter (yeah, they assume you're using the tools they make lol) does.

So:
all tests pass = good relay
all tests fail = good relay
some tests pass/fail = bad relay
 

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Discussion Starter · #30 ·
No prob. PM me if you need a copy of the service manual.
Oh Ive got it, and now my brain hurts from reading the whole section on testing and how to read their diagrams .. I can wire anything in a residential home from the service entrance back, hell I even do service entrance, some commercial and 3 phase electrical... But this 12v stuff overwhelms me everytime and then I don't do it enough so by the next time, I can't remember a continuity test from a resistance, something about Ohms Law and Diodes and Relays that aren't switches and switches that are relays... I normally pay my billbilly motorcycle savant mechanic in Beer and aqcuisitioned Pot to handle anything electrical but again, stranded 2k miles from home and ya.... Wish me luck, here I go...
 

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In those pictures in post #8, are the nice clean copper contacts sitting slightly proud of the plastic backing?
What do the parts that slide over them look like? I assume they are kind of like a flat copper shoe??
 

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The whine is the fuel pump. It's high pressure being an injected engine.
But if it's also saying it feels humiliated and/or violated you may have a millenial squirrel stuck under there.
 

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Discussion Starter · #33 ·
In those pictures in post #8, are the nice clean copper contacts sitting slightly proud of the plastic backing?
What do the parts that slide over them look like? I assume they are kind of like a flat copper shoe??
They arent proud, but i did disassemble the entire rthing, the other side of the switch the "Shoes" as yuou put it are spring loaded, definitely proud of their plastic housing, and they have raised bumps where they contact the other side, spings cleaned, checked for extension, and confirmed continuity after reassembly.
 

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I'm no sort of electrical engineer, I don't even play one on TV (or the internet). Based on what I see on the diagram I can't see a failure mode of the 'relay unit' that would cause the bike to run only when in the start position. That said if the cut off switch is testing good then I also don't see a way that the wiring between the switch and the rest of the bike could be 'broken' in such a way that the bike only runs when in the start position. Bascially I've got no freak'n clue.

The relay unit's whole job is to make sure that the starter can only be engaged when the bike is in neutral, or when the side stand is up and the clutch is pulled in.
The engine cut off switch works by cutting power to the ignition coils.

Red/white into the switch is +12V. Red/Black into the switch connects to the + terminal on the ignition coils, supplying them with power and providing spark to the engine.
The same red/black is connected to the 'relay unit' but it is providing +12V for the relay coil. The only possible way I could see it working is if you've got +12V back-feeding the circuit, however if that were the case you wouldn't be able to start the bike because you've have no difference in current on the oposite sides of the relay coil.
This is the 'blown up' version of the circuit inside the 'relay unit' from the manual:
Parallel Slope Rectangle Font Diagram

Font Screenshot Number



Next steps - aka shots in the dark - aka WAG
1. If you've got a code reader (or can borrow one) I'd clear the codes, attempt to start the bike, then read the codes and see if there is anything sensible listed. The manual hints that a bad relay unit could throw a code.
2. Plug your wiring all back together, key on, cut off switch in 'run' position. Put your meter in DC volts. Probe the back of the plug for the cutt off switch and confirm you've got +12V on the red/black wire.
3. Do an idiot test - make sure you're firmly holding the brakes in case the starter does engage when you don't expect it to - otherwise you'll drop your bike
3.a - with the bike in gear and the side stand down see if you can start the bike
3.b - with the bike in gear and the side stand down and the clutch lever squeezed see if you can start the bike.
3.c - with the bike in gear and the side stand up see if you can start the bike.
3.d - with the bike in gear and the side stand up adn teh clutch lever squeezed see if you can start the bike.
3.e - with the bike in neutral and the side stand down see if you can start the bike.
4. Unplug the 'relay unit'. Key on, cut off switch in 'run' position see if you've got +12V on the red/black wire in the plug. Move the cut off switch to 'start' - you should still have +12V on the red/black wire. Key on, cut off switch in the 'off' position, check for +12V on the red/black wire in the plug.

If you need more detail on how to test for the +12V with your meter let me know and I'll give you detailed instructions.
 

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I'm no sort of electrical engineer, I don't even play one on TV (or the internet). Based on what I see on the diagram I can't see a failure mode of the 'relay unit' that would cause the bike to run only when in the start position.
My thinking was that if one of the diodes in the relay fails in a way that causes current to flow in an unintended direction and weird problems follow. I just don't have the patience to figure out exactly how LOL
 

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I was reading on another forum about a guy with a similar problem, except his bike cut out when the fuel pump stopped priming. Turned out he had been playing with things and installed the tip over switch upside down.
Don't think you have done that, but perhaps one of the safety relays (Clutch, Sidestand, Tip over etc) has suddenly flaked out. I've noticed that relays on bikes are not water or dust proof, so...
P.S. Batteries fail fast in Phoenix - it's the heat
 
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