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Thread: Fusing a /5

  1. #1
    --Tony AnnapolisAirhead's Avatar
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    Fusing a /5

    Any pointers to how or articles on doing this?. I just got new toy but want to do the typical upgrades.
    '83 R100RT'd
    '71 R75/5 SWB
    '06 KLR 650

  2. #2
    Administrator 20774's Avatar
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    Snowbum has wiring diagrams of before and after fusing...might be a good thing to copy:

    http://bmwmotorcycletech.info/SchemSlash5.htm
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    --Tony AnnapolisAirhead's Avatar
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    Thanks Kurt. I only see a single fuse on Snowbums post. For some reason, I thought there were two like my '83 R100, no?

    The reason I ask is because when I bought the bike the PO had installed the very cool looking but nearly useless (no, completely useless) mirrors in the headlight bolts. These mirros do not have a nut on the inside of the light, but should. He had inadvertently trheaded the right side into the metal bracket the has the flasher mounted to it and pinches the left turn signals positive wire. So imagine my horror when I got it over to a friends place, still on my trailer and we ran through where-the-heck-are-the turn-signals routine and I noticed the left barely working, then not at all ...and saw smoke coming from the headlight bucket! D'oh! Can't imagine why he wouldn't have removed the headlight to check things first, but he didn't and must not have used turn signals on his next ride. I've since cut down the threaded length of the mirror stem and put a rubber washer with a nut on the inside of the headlight as well as the chromed external nut.

    Anyway, smoldered the ignition harness which doubles are the turn signal and brake light harness. So, $100 and 6 hours later, I was enjoying the bike. I'm thinking fusing would prevent the fire which surely would have happened in a rather unsavory, middle of nowhere location, had we not run through the switch locations. Yes?

    I thought about PMming you or Mr. Strickland, but figured for the long haul, it might be better to have a searchable post. My searches turned up with a lot of false positives. So this will help.

    Cheers.
    '83 R100RT'd
    '71 R75/5 SWB
    '06 KLR 650

  4. #4
    rocketman
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    plug it in to a high tension line, that will "fuse" the entire harness in no time!


    (Please accept my apologies, but in my current mood, resistance was futile so I just went with the flow, not intentionally meaning to appear negative. Normally I am very well grounded but I was overcome by the electromotive forces at work in a moment of weakness; however I should recover in short order).

    RM

  5. #5
    Administrator 20774's Avatar
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    Quote Originally Posted by AnnapolisAirhead View Post
    Thanks Kurt. I only see a single fuse on Snowbums post. For some reason, I thought there were two like my '83 R100, no?
    Hmmm...I only looked at it quickly, but I thought I saw two "blocks" with wires going in and out...figured thosed were the fuses.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
    --Tony AnnapolisAirhead's Avatar
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    Quote Originally Posted by rocketman View Post
    plug it in to a high tension line, that will "fuse" the entire harness in no time!


    (Please accept my apologies, but in my current mood, resistance was futile so I just went with the flow, not intentionally meaning to appear negative. Normally I am very well grounded but I was overcome by the electromotive forces at work in a moment of weakness; however I should recover in short order).

    RM
    Thanks for the tip, but er...
    Me thinketh you've been stand too close to the high tension power lines Jeff. Stop pushing when you feel resistance on the que tip.
    '83 R100RT'd
    '71 R75/5 SWB
    '06 KLR 650

  7. #7
    --Tony AnnapolisAirhead's Avatar
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    Quote Originally Posted by 20774 View Post
    Hmmm...I only looked at it quickly, but I thought I saw two "blocks" with wires going in and out...figured thosed were the fuses.
    Hmm, I think the turn signals, brake light and headlight(?) should be fused, but I'm just going from memory and not sure if that's right. I'll do some more digging.
    '83 R100RT'd
    '71 R75/5 SWB
    '06 KLR 650

  8. #8
    James.A
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    A good general fusing for an early, unfused /5 would be to splice in an inline fuse on the wire that supplies battery voltage to the main switch in the head light shell. That is the trip point for all current distributed throught the electrical system.

    Both of my /5's, being '73's, have 2 fuses incorporated in the original wiring scheme, in holders attached inside the headlight bucket. If you have access to a later /5 wiring diagram, it should be easy to trace down the points where they terminate and retro-fit accordingly.
    Last edited by woodnsteel; 11-02-2010 at 03:31 PM. Reason: spelling

  9. #9
    --Tony AnnapolisAirhead's Avatar
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    Thanks Jim. What sized fuse do you recommend?
    '83 R100RT'd
    '71 R75/5 SWB
    '06 KLR 650

  10. #10
    James.A
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    I just checked the fuses in my white 750. They are rated 25amps. The main thing to consider would be that the fuse needs to be capable of holding up the lights without popping. You might be able to splice in a fuse holder on the small wire on the battery positive. The large positive cable delivers current, un-fused to the starter motor only.

  11. #11
    Rally Rat
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    Quote Originally Posted by rocketman View Post
    plug it in to a high tension line, that will "fuse" the entire harness in no time!


    (Please accept my apologies, but in my current mood, resistance was futile so I just went with the flow, not intentionally meaning to appear negative. Normally I am very well grounded but I was overcome by the electromotive forces at work in a moment of weakness; however I should recover in short order).

    RM

    You get extra points for using the words "electromotive force". I really got a charge out of that. Generated several chuckles.

  12. #12
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    Fuses

    Quote Originally Posted by woodnsteel View Post
    I just checked the fuses in my white 750. They are rated 25 amps.
    Wow, 25 amps!. My '78 R100/7 can't be that different and it still has the original 8 amp fuses in it, as per the wiring diagram. I know they're original as I've had the bike since new and have never changed a fuse

  13. #13
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    best place for fuses is after the on/off switch in headlight bucket
    not between battery and on/off switch

    I would not fuse the headlight itself - I agree with older automotive
    thinking - that is - when driving at night the headlight should never
    suddenly fail because of a fuse - I would rather smoke the harness
    and gradually go dim than suddenly go black and into the ditch

    In the era of shunt dc generators no fuse was necessary because
    if there was a short in the system the field would collapse and
    the output decline - thus protecting the generator and wiring if
    wiring was sized large enough

    Early /5 had no fuses like the prior /2 models had no fuses

  14. #14
    rocketman
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    Quote Originally Posted by krpreston View Post
    Wow, 25 amps!. My '78 R100/7 can't be that different and it still has the original 8 amp fuses in it, as per the wiring diagram. I know they're original as I've had the bike since new and have never changed a fuse
    That’s what mine has as well. Or did till I wired up some in-line holders and now use 10 amp. I did that because I have a barn door on mine and replacing the bullet nosed fuses by feel was just too damn hard. As for wiring, the headlight is not fused on mine. turn signals, running lights (also Parking lights including rear tail light with key in the normal running position), brake light and instrument lighting are all that's fused on mine. Bike will start and run fine without any fuses and headlight will remain on (not sure about high beam but I'd bet it does work).

    RM

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