Neutral light switch

[tmworks]

Ok, before I tear into it hopefully someone can give me a heads up.
To get my 79 SF to run I had to take the wire that goes to the neutral light switch in the engine and ground it to the frame.
Any advice would be appreciated.

[erithanis]

Have you taken a look at the wiring diagram for that bike? I had to do some trouble shooting before and it helped a lot, I can probably give a tutorial on how to read it if one doesn't exist.

Don't know about your particular problem though.

[oseaghdha]

The neutral switch shares a circuit with the pickup coils. You got some funky connectors to clean. Probably lost a ground. Does it run in neutral?

[tmworks]

Well, the scenario happen a few times. After washing the bike it would start up in neutral, but when I put it into gear, 2 of the cylinders would drop out ( something was grounding out). After the bike fully dried out, all was well.
Then after one washing, the same 2 cylinders would drop out and they never fired after that. I tinkered with it awhile and by coincidence took the neutral position wire( I think that’s what it was because the light is on all the time now) that goes into the engine and grounded it to the frame and the bike ran fine. Been that way ever since. It would be nice to have that light only come on when in neutral.

[TopCatGr58]

Hey TMWorks,

The Clymer's wiring diagrams in the LINKS forum have a known error regarding the neutral light switch. The Neutral light grounding wire is light blue, but when you follow it to the PickUp Coil plug, you'll see the neutral switch is drawn to the red/black power wire=wrong! IT should be drawn to the light blue wire, cause it's just a switch that completes the circuit to ground so the bulb will light!

The bike will start whether in neutral or not with the clutch pulled in/disengaged. The neutral light doesn't turn OFF the TCI! But providing the ENGINE with a separate GROUND before it would fire sounds like you may have some grounding issues. There's a separate grounding strap on the back of the engine to the frame, may be very badly corrroded?

I would check your connections, grounds first!
T.C.

[oseaghdha]

That happens on my 79SF also. Seems to be an issue with these bikes. No one has cured it yet.

[oseaghdha]

Originally posted by TopCatGr58
Hey TMWorks,

The Clymer's wiring diagrams in the LINKS forum have a known error regarding the neutral light switch. The Neutral light grounding wire is light blue, but when you follow it to the PickUp Coil plug, you'll see the neutral switch is drawn to the red/black power wire=wrong! IT should be drawn to the light blue wire, cause it's just a switch that completes the circuit to ground so the bulb will light!

The bike will start whether in neutral or not with the clutch pulled in/disengaged. The neutral light doesn't turn OFF the TCI! But providing the ENGINE with a separate GROUND before it would fire sounds like you may have some grounding issues. There's a separate grounding strap on the back of the engine to the frame, may be very badly corrroded?

I would check your connections, grounds first!
T.C.

My Yamaha diagram shows the Neutral switch coming off one leg of the pickup coil.

[tmworks]

thanks for the info. I'll check the ground strap.

[TopCatGr58]

Hey Dan,

Are you saying your OEM Yamaha Official wiring diagram from the USER's Manual?? IF so, then Yamaha made a mistake!

IF you look at the wiring diagram for the 81H/SH in the LINKS or on the XS-XJ Cdrom, you'll see that they corrected the error, and have the neutral light connected to the light blue wire like it's supposed to be, the one coming from the neutral LIGHT! It's just using the PU coil connector to house the wire!
T.C.

[D. P. Larmee]

I've had the exact same thing happen to me on more than one occasion. Either I wash the bike or I get stuck in a good rain storm and it runs fine in neutral but as soon as I put her in gear, blammo drops two cylinders. It usually only lasts a few blocks. It seems that as the engine warms up and the moisture burns off, they come back on line. I posted about this years ago and consensus was either bad plug caps or wires, but these have all been replaced and the problem still persists, so I'm thinking that there must be more to it. It never really lasts long enough to diagnose, but the fact that yours did it permanently is not real reassuring. It sounds like it almost has to be a short somewhere in the connector that is shared with the pickup coil. I will have to take a look at that connector and see if there is something visibly wrong. If you figure it out, please let us know what the problm was, as it sounds like there may be a few of us out here with similar issues.

[tmworks]

Will do D.P

Keith

[oseaghdha]

First: I was looking at the schematic wrong. The convention they used does not show the individual wires after the plug. They have only a generic two line connection representing many wires, so the neutral switch was only shown to be in that bundle.

Second: This has happened to me three times. First was at the car wash, second I washed it at home. Both times, after having sat overnight, it worked fine.

Last time it happened, the bike was at work during a nasty thunderstorm. It did the neutral good/ in gear bad thing. had no choice but to head for the house. If I put it in neutral at the stop light, I had a couple of beats to get rolling before it crapped out again. In a moment of frustration, I flicked the kill switch off and on. It brought back the two cylinders, again for about a second and a half. I repeated this several times until it stayed up. This was over a period of 4 or 5 miles, in which time the engine may have warmed up enough to dry out whatever was causing the fault.

This had the appearance of a charge/discharge scenario. It was not a sudden on/off, more like it had to build up for a brief time before failing. Just another clue.
The neutral switch is obviously providing a ground path for something in the igniton circuit. Likewise, it seemed the kill switch was unloading the circuit enough to allow a brief moment of normal operation. I did not have the opportunity to determine which set of cylinders was affected.

[randy]

Inside the pickup coil harness the pickup wires are spliced (crimped) between the flexible wire and regular wire. You may have water getting in there, frayed wires and loose crimps. I would unwrap the harness and re-do the connections, waterproof 'em with some liquid rubber insulation goop ( I think that's the technical term). I've seen the goop at large electrical supply houses, or if you're lucky, maybe the depot will have it.

Then re-wrap the harness nice and tight.