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#713228 - 10/30/17 4:51 pm Wiring harness for 1969 t120r and tr6c  
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jchildr Offline
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jchildr  Offline
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Nashville TN
Can anyone tell me the difference between wiring harnesses 54955719 (for the 1969 tr6c) and 54955257 (for the 1969 t120r)? Can they be interchanged without modifications? Also, can you tell me what gage wire is used in these harnesses. Thanks.

Last edited by jchildr; 10/30/17 5:36 pm.
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#713237 - 10/30/17 6:49 pm Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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BrettF Online content
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Geneva, Switzerland
hello, my understanding is that originally the wires were similar to this 14xSTRANDS, RATED 8.75 AMPS, OD 1MM SQ (.040") while I was recommended to use this : 32xSTRANDS,RATED 16.5 AMPS, OD 1MM SQ(.040").

As for the difference between the two harnesses I do not know. Two horns vs. one are the only difference I can think of though. a look at the schematic should clarify this.


3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
#713241 - 10/30/17 8:21 pm Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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koan58 Online content
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Hi jc,
A quick look at the TMS Nottingham site lists all models as being the same for any year in the late 60's. I don't know if there were any differences, electrically, between the T120 and TR6C, but I am sure they would be trivial (eg maybe indicators or not) and I'd expect the harness to have provision for all the various models.
For any more detailed reassurance, wait for Stuart to come along, if he's not on holiday again! He knows the ins and outs of a wiring loom's arse! Dave

#713263 - 10/30/17 11:35 pm Re: Wiring harness for 1969 t120r and tr6c [Re: koan58]  
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russrudolph Online content
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I have a 1969 tr6c that I received in pieces. I bought a new Lucas harness for the bike. Harness was not equipped with the kill switch wires. I also have a 1969 tr6c that I have owned for 40 years and it has wires for the kill switch. I purchased a new Lucas 719 harness but have not installed harness yet. Just left 2 wires from kill switch loose inside tank and frame. New 719 harness in a drawer too lazy to change.

I also think wiring for ammeter is different bur not sure.

#713291 - 10/31/17 1:47 am Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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KC in S.B. Online content
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Santa Barbara, California
So,...... Which one are you working on? I have an original NOS cloth covered harness for the '69 TR6C bought years ago and did not use. P/N on the old tag is 54955719. Wired the bike myself, and did so as Negative Ground/earth/minus/ whatever you care to call the low. I happen to see this post today as I was picking through things to sell.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#713293 - 10/31/17 2:12 am Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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tiger_cub Offline
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australia
TMS actually list 3 harnesses for 1969 - MC127 for T120R, MC133 & MC134 for TR6C (main differences are no ammeter on TR6C plus options for front brake switch & kill switch as noted above).


1970 TR6C
1972 TR6C
#713295 - 10/31/17 2:21 am Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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KC in S.B. Online content
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KC in S.B.  Online Content

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Santa Barbara, California
How about the dangling Blue Capacitor Can?

Last edited by KC in S.B.; 10/31/17 2:22 am.

Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#713327 - 10/31/17 10:30 am Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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Stuart Online content
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Hi,

Originally Posted by jchildr
wiring harnesses 54955719 (for the 1969 tr6c) and 54955257 (for the 1969 t120r)? Can they be interchanged without modifications?

How long is a piece of string? Are the ones you're looking at original? If so, they're fifty years old.

If they aren't original, who were they made by? In theory at least, it should be possible to fit a T120R harness to a TR6C and simply join the Brown/Blue and Brown/White in the headlamp (that attach to the ammeter on a T120R or TR6R). In practice, some modern harness makers' interpretations of 'original' vary ... somewhat ... cool

Also bear in mind that certainly originally, a single harness didn't always make all the connections between everything; there were small harnesses to connect, say, the main harness and the ignition switch. Modern harness makers don't always supply these, or do so at extra cost ... frown

Originally Posted by jchildr
what gage wire is used in these harnesses.

Original wire gauges vary. Ime, original wires were based on 32SWG (No.32 (British) Standard Wire Gauge) strands; wires to individual components were 14-strand, rated for 7.5 Amps, the wire between ignition switch and the junction of individual components' White wires was 28-strand, rated for 15A, the Brown/Blue, Brown/White and main Red were 42- (-ish) strand, rated for 22.5A.

Lucas did supply original harnesses with all-14-strand 32SWG wire but ime only '71-on. Note that the rating of either 14-strand Imperial or metric wire (that Brett posted) used to link rectifier and Zener is exceeded by the alternator output above about 2,000 rpm. In a '69 harness, if you find 14-strand used for main Red (to battery), Brown/Blue, Brown/White and either White or White/Blue from the ignition switch, the harness is poor-quality. frown

The problem of modern wire gauges is vexing but worth taking the time to understand, if only because it'll inform your choice of harness and also you will need to make changes and/or repairs at some time in the future:-

. The vast majority of connections in Britbike harnesses, including '69, are 3/16" o.d. (4.7 mm. equivalent, be wary of any supplier that quotes "5 mm.") 'bullet' terminals joined by tubular black-insulated 'snap connectors'. The most important criterion certainly of original-looking bullets is they stay on the conductor by friction, having been squeezed by a hex. crimping tool - Lucas stopped soldering years before '69.

. Brett mentioned the modern metric equivalent of one of the original Lucas wire gauges - "14xSTRANDS, RATED 8.75 AMPS, OD 1MM SQ". Original-looking crimp-on bullet terminals are only available as standard for this wire gauge, plus the metric 28-strand and 44-strand equivalents. None are available for any other wire gauges, including original Lucas, AWG (American Wire Gauge), the one Brett says he was "recommended to use" or any of the weird ones some pattern harness makers seem to be able to find. Modern bullet terminals vary a little by how much they can be squeezed when crimping; in certain circumstances, certain bullets can likely be make to 'work' on conductor they aren't sized for but it's a minefield. frown

Finally, bear in mind that almost any off-the-shelf harness will be a good or bad copy of an original, so it'll have connections to separate rectifier 'n' Zener, points, condensers, etc.; if you're considering modern reg./rec. (modern Zeners are particularly poor-quality eek) and/or e.i., as you're in the US, I'd strongly recommend at least talking to British Wiring; I know they use the aforementioned modern metric equivalent wire, terminals and connectors; aiui they can supply a harness without rectifier/Zener/points/condensers connections you then otherwise have to tape up ...

Hth.

Regards,

#713338 - 10/31/17 12:42 pm Re: Wiring harness for 1969 t120r and tr6c [Re: russrudolph]  
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Stuart Online content
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Hi Russ,

Originally Posted by russrudolph
I have a 1969 tr6c that I received in pieces. I bought a new lucas harness for the bike. Harness was not equipped with the kill switch wires. I also have a 1969 tr6c that I have owned for 40 years and it has wires for the kill switch.

I'd be interested if you could clarify? The contemporary harnesses and (push-to-break button) kill switches I've seen, the White supply wire to the coils has a bullet terminal:-

. either into a big snap connector with other components' White wires and the (usually) White/Blue wire from the ignition switch;

. or into a single snap connector into a short White wire into a more-permanent crimped insulated connector with the other aforementioned wires;

. inside or around the headlamp area.

A kill switch then has two wires with bullet terminals, one's connected into the aforementioned snap connector in place of the coils' White wire, the other's connected just to the coils' wire with another snap connector?

Regards,

#713351 - 10/31/17 2:20 pm Re: Wiring harness for 1969 t120r and tr6c [Re: Stuart]  
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russrudolph Online content
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russrudolph  Online Content
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USA, WA state
The original harness that cam with the 1969 tr6c I bought in 1975 has bullet connector to the white coil wires.
The new cloth wire harness for the 1969 tr6c I bought in pieces. Cloth Harness purchased from forum advertiser did not have bullet connectors for the kill switch. Only noticed this after installation. I have not fixed the kill switch. Again very lazy. I have only ridden bike a few miles since the rebuild.
I purchased a new Lucas harness 54955719 but have not opened the package. Will look at harness to see if it has bullet connectors for kill switch. Just thought it would be nice to have original 54955719 harness in reserve for my 3 1969 tr6c's

I have seen the on eBay a wiring harness to add the blue capacitor to a 120 harness.

#713368 - 10/31/17 4:45 pm Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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jchildr Offline
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Nashville TN
Thanks everyone. The reason for this post is as follows: I have a 1969 T120R. My builder wrote down all the part numbers used to restore the bike. The part number he wrote down for the wiring harness was 54955719. I could not reach him at that time to verify. I finally was able to reach him after I made the post. He wrote down the wrong part number. He should have written down 54955257.

#713726 - 11/03/17 4:00 pm Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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C.B.S Online content
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I'm pretty sure the TR6C has the 2MC capacitor. Also keep in mind that the headlight shell has different switches and indicators then a STD T120R

#713835 - 11/04/17 3:45 pm Re: Wiring harness for 1969 t120r and tr6c [Re: C.B.S]  
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Stuart Online content
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Stuart  Online Content
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Scotland
Hi,

Originally Posted by C.B.S
I'm pretty sure the TR6C has the 2MC capacitor.

2MC capacitor can be fitted to anything; if the wiring harness doesn't have the connections in the Brown/Blue wire and a Red wire, just connect the cap.'s -ve and +ve terminals to battery terminals.

Originally Posted by C.B.S
Also keep in mind that the headlight shell has different switches and indicators then a STD T120R

Depends which year; the o.p. specifically said '69. All '69 have a headlamp hi/low switch and horn button; only difference on a C is only the horn button's on the handlebar, the hi/lo switch is in the headlamp shell; assuming by "indicators", you mean the o.p. warning and high beam warning, all '69 have 'em both in the headlamp shell.

Hth,

Regards,

#715408 - 11/16/17 7:35 pm Re: Wiring harness for 1969 t120r and tr6c [Re: jchildr]  
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jchildr Offline
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jchildr  Offline
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Nashville TN
Hello Stuart. I called British Wiring to ask about their wiring harness for my 1969 T120R. The part number is MC27PB. They said this harness is built totally with 14 strand British (SWG) wire rated at 8 amps. Do you think this harness is poor quality? They also said this wire is comparable to 18 (AWG) wire. 18 (AWG) is rated at 13 amps. This does not seem comparable to me. What am I missing here? I know you can't believe everything you here and read, but there are lots of charts comparing British (SWG) to American (AWG). The chart I saw says 14 strand SWG is rated at 13 amps. There is also a Wire Gauge Comparison Chart in my 1969 Triumph Workshop manual. In the first column it has the number for the wire gauge. In the next two columns, it has the Imperial (SWG) diameter size in inches and millimeters. In the next two columns, it has the American (AWG) diameter size in inches and millimeters. In this chart, 18 gauge is .048 in (Imperial SWG) and .040 in (American AWG). I actually measured the bare wire from both 14 strand SWG and 18 gauge AWG and I got the same measurement as the chart in my 1969 Triumph Workshop manual. I understand amperage is determined by the diameter size of the bare metal of the wire. If this is true, then these two wires should have approx. the same amperage or current carrying capacity. Am I correct in this assumption? Any thoughts would greatly appreciated. The following website has a good article explaining British (SWG) wiring. https://books.google.com/books?id=9...%20stranded%20wire%20numbers&f=false


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