Author Topic: Spare plug under tank  (Read 959 times)

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Offline Sketch

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Spare plug under tank
« on: January 19, 2018, 05:10:30 PM »
Hi ,I have a 1973 TX500,underneath the tank by the coils is a electrical connector with nothing going to it does anyone know what this was for?,cheers,dave.

Offline guylr

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Re: Spare plug under tank
« Reply #1 on: January 20, 2018, 12:11:04 AM »
If the wire colors are black, yellow and green/white then it is for the lamp checker unit that checks to see if the stop light is burned out and flashes the warning light on the light panel.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline Sketch

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Re: Spare plug under tank
« Reply #2 on: January 20, 2018, 09:12:35 AM »
Hi guy,itís not that,it is a female plug with five wires going to it,the colours are green/red,brown,white/red,orange and black,I canít seem to to find a male plug to fit it,cheers,dave.

Offline CrouchyUK

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Re: Spare plug under tank
« Reply #3 on: January 22, 2018, 12:42:16 PM »
Ah- the mysterious extra connector surfaces again!  This connector has been reported by a couple of TX500 owners over the years and we never got to the bottom of it.  Here's my theory.....

If you look at the underside of your TX500, TX500A or XS500B meter bracket you will notice that there is an extra warning light hole in between the LH and RH indicator lamps.  And in fact if you remove the rubber housing you will see that there is a large hole in the casting to suit- the fascia plate blanks it off on all USA and European models.  Another "lost in history" TX500 modification. This warning light was for the Japanese market speed warning light required by law then.  It looked like this- and the speedo was also marked up with a 80kph warning, which was when the light came on.  This bike is a low number TX500 imported into the USA from Japan.




If you look on the TX500/TX500A harness routing guide in the FSM- they still show a relay guess what- under the tank!  The relay appears on the parts list as 371-83581-00, but was never fitted to our bikes as far as I can see.  I did try and search this part out one time- all I found was reference to the Japanese market SR400 which appears to have had the same arrangement.




Both the main wiring harness and the instrument cluster harness part numbers changed from the TX500 to the TX500A, which is when I believe this connector was discontinued- we just never noticed because we expected the part numbers to change anyway- with the addition of the brake lining checker system on the TX500A.  I have never heard of this connector on a TX500A.

I did read that some other Yamaha bikes of the period also had this speed checker relay- SR400 and others- and that it was a bit of a cludge as it operated off engine speed in some way- rather than bike speed.  So what did always bother me about the wiring colours that members have reported is the pink wire- which has always been the LH coil to points wire.  So maybe this relay operated off the ignition pulses to get a "speed" input.  Brown of course is ignition live, black is earth to frame.  That leaves green/red and white/red which do not appear on any wiring diagram at all.

What would be great- is if someone with this connector tested that pink wire to see if it is connected to the LH points circuit.  This would be internal inside the harness like the condensor feeds- but a simple continuity test would get it.

Also- if someone had access to a wiring diagram of an early SR400- it may show those other wire colours and explain how it all worked!


1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2

Offline Sketch

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Re: Spare plug under tank
« Reply #4 on: January 23, 2018, 09:20:47 AM »
Hi crouchy,thanks for your reply it is very interesting,later on in the week I will check the pink wire to see if it is connected to the points and let you know,cheers,dave

Offline Sketch

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Re: Spare plug under tank
« Reply #5 on: January 23, 2018, 03:46:37 PM »
Hi crouchy,checked the wiring out today and the orange wire from the plug is connected to the points,cheers,dave

Offline CrouchyUK

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Re: Spare plug under tank
« Reply #6 on: January 24, 2018, 01:32:00 PM »
Thatís great thanks- another mystery nearly solved!
1975 Honda CB200T (2) - 1975 Yamaha XS500B (2) - 1976 Yamaha XS500C
1977 Yamaha RD400D - 1977 Yamaha XS500D - 1978 Honda CB550K - 1980 Honda CB400N
1980 Honda CB900FA - 2000 Kawasaki ZX6-RG2 - 2002 Suzuki GSX-R1000K2

Offline dailydose1

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Re: Spare plug under tank
« Reply #7 on: February 16, 2018, 11:54:21 PM »
I too have this same connector, and have been studying the damn wiring diagram for many of hours trying to figure out how i could be missing where this went too. lol