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Author Topic: Carb problem on yamaha xs750  (Read 572 times)

Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #10 on: Sep 04, 2018, 08:49:42 »
Fantastic I will have a go at that today and post an update. Thanks!

Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #11 on: Sep 05, 2018, 08:48:21 »
UPDATE

10mm spanner magnetizes to the right side engine cover no problem.

3 white wires from stator harness all have 0.6-0.7 Ohm between them in all combinations. Manual says 0.48 Ohms +/-10% at 20dge if I remember right from what I read yesterday. So it would appear I am  a bit on the high side, how bad is that?
As well none of the 3 white wires are grounding.

Everything I found online says that that harness should plug into the REG/REC which I assumed was the one square-ish unit mounted to the frontside of the battery box that has what looks like cooling fins on it. However the plug from the stator with the three white wires (and a yellow wire) plug into a small gold relay looking unit mounted behind the battery box on the left side.

What is this called? I cannot seem to find anything out about it... is plug even plugged into the right spot...?


Offline datadavid

  • Posts: 1371
Re: Carb problem on yamaha xs750
« Reply #12 on: Sep 05, 2018, 08:58:27 »
UPDATE

10mm spanner magnetizes to the right side engine cover no problem.

3 white wires from stator harness all have 0.6-0.7 Ohm between them in all combinations. Manual says 0.48 Ohms +/-10% at 20dge if I remember right from what I read yesterday. So it would appear I am  a bit on the high side, how bad is that?
As well none of the 3 white wires are grounding.

Everything I found online says that that harness should plug into the REG/REC which I assumed was the one square-ish unit mounted to the frontside of the battery box that has what looks like cooling fins on it. However the plug from the stator with the three white wires (and a yellow wire) plug into a small gold relay looking unit mounted behind the battery box on the left side.

What is this called? I cannot seem to find anything out about it... is plug even plugged into the right spot...?

Those .2-3 ohms may well be error margin from the multimeter, as long as they are even and not grounding out it should be good. Three white wires can be disconnected and measure output with running engine between wires. Should be 60-70v AC iirc. Gold relay looking box sounds wrong, might be that rectifier part fried and some p.o installed something else, unclear what..
Sounds a lot more like the mechanical regulator part from earlier xs750's..
 should have cooling fins if its a rectifier unit. From there it should send positive and negative dc to battery. Does it have two wires coming out of it besides the three white ones?

Skickat frŚn min Pixel via Tapatalk
« Last Edit: Sep 05, 2018, 09:04:55 by datadavid »

Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #13 on: Sep 05, 2018, 12:06:36 »
It has three whites and a yellow wire all from the same harness going into that gold relay looking unit, which has a rubber holder and everything and fits into the battery box. Looks stock to me. Iíll get a photo today and post it. No wires come out of this unit and head anywhere else which seems wrong... unless itís sending back to the right side cover area via the yellow wire? I also have a cooling fin unit on the other side of the battery box that looks exactly like what a reg/rec unit on google. Could something just be plugged in wrong?
 Iíd have to double check but I believe the black and green wires from the generator head to the rectifier unit and in the wiring diagram from the manual it makes it look like two different units...

It seems to be wired up as per the first diagram but has a unit that looks like that in the second diagram (which is the 2D)


I will take some photos this afternoon and post them 


Offline datadavid

  • Posts: 1371
Re: Carb problem on yamaha xs750
« Reply #14 on: Sep 05, 2018, 12:18:53 »
Something sounds very off! The black and green Should go to the regulator component, which looks just like a relay box..
It has three whites and a yellow wire all from the same harness going into that gold relay looking unit, which has a rubber holder and everything and fits into the battery box. Looks stock to me. Iíll get a photo today and post it. No wires come out of this unit and head anywhere else which seems wrong... unless itís sending back to the right side cover area via the yellow wire? I also have a cooling fin unit on the other side of the battery box that looks exactly like what a reg/rec unit on google. Could something just be plugged in wrong?
 Iíd have to double check but I believe the black and green wires from the generator head to the rectifier unit and in the wiring diagram from the manual it makes it look like two different units...

It seems to be wired up as per the first diagram but has a unit that looks like that in the second diagram (which is the 2D)


I will take some photos this afternoon and post them

Skickat frŚn min Pixel via Tapatalk


Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #15 on: Sep 05, 2018, 12:27:45 »
Just was doing some more looking online at what that gold unit could be and stumbled across this... which is a blurry photo but Iím 99% sure that is exactly what the plug coming from the stator with the three white wires is plugged into...

Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #16 on: Sep 05, 2018, 22:57:45 »
UPDATE

alrighty, so it was plugged in wrong... stupid.

The photo below is the gold relay that the stator harness was plugged into. I found the plug with 3 white wires coming off the Reg/rec unit and swapped the plugs around...

Now it seems to be charging great so thatís a plus. On the downside the gold relay has a good rattle to it when I shake it so Iím assuming itís trash. Also now the headlight doesnít work or blows the 10A fuse almost instantly when the key is turned on, which is new. I took the gold relay to a shop and asked whatís what and they told me it comes up as the flasher relay.

BUT the signals work just fine. Always have. So Iím guessing that itís a relay for the headlight and cause itís broke the fuse is blowing...? Does that make sense?

I attached some photos of the relay and in the background is the holder for it. The second photo is of the plug that was swapped with the stator plug so is now plugging into the relay. I canít find anything in either wiring diagrams I have that match or look like this plug at all, any ideas?

Offline datadavid

  • Posts: 1371
Re: Carb problem on yamaha xs750
« Reply #17 on: Sep 06, 2018, 00:57:57 »
Maybe someone stuck a flasher relay in place of the headlight relay, seen worse!
UPDATE

alrighty, so it was plugged in wrong... stupid.

The photo below is the gold relay that the stator harness was plugged into. I found the plug with 3 white wires coming off the Reg/rec unit and swapped the plugs around...

Now it seems to be charging great so thatís a plus. On the downside the gold relay has a good rattle to it when I shake it so Iím assuming itís trash. Also now the headlight doesnít work or blows the 10A fuse almost instantly when the key is turned on, which is new. I took the gold relay to a shop and asked whatís what and they told me it comes up as the flasher relay.

BUT the signals work just fine. Always have. So Iím guessing that itís a relay for the headlight and cause itís broke the fuse is blowing...? Does that make sense?

I attached some photos of the relay and in the background is the holder for it. The second photo is of the plug that was swapped with the stator plug so is now plugging into the relay. I canít find anything in either wiring diagrams I have that match or look like this plug at all, any ideas?

Skickat frŚn min Pixel via Tapatalk


Offline clem

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Re: Carb problem on yamaha xs750
« Reply #18 on: Sep 06, 2018, 10:05:23 »
That is the correct headlight relay. This keeps the headlight off until the bike is running.

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Offline matt.k

  • Posts: 13
Re: Carb problem on yamaha xs750
« Reply #19 on: Sep 06, 2018, 12:08:47 »
Okay awesome thank you! Would the faulty relay be the reason the headlight fuse blows when the key is turned on? Or do I have some other electrical mystery to solve?

Also I am guessing I will need to replace that relay with a duplicate, not just any relay?