bypassing black relay pre 01 model
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Thread: bypassing black relay pre 01 model

  1. #1
    Senior Member supachip1's Avatar
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    bypassing black relay pre 01 model

    hi guys

    does anyone know how the black relay works?

    i have just re-built a 98 for a friend and remember it had a wire spliced in just before the connector block allowing the relay to somehow work or complete the circuit..or what ever it does, i can't remember where this wire went to but now have another bike with the same issue….i removed the wire on my friends, re-taped and replaced the relay so can't check it now
    I have spend hours rewiring previous hash ups due to lack of replacement parts and don't really like to bodge stuff, but i would rather splice a wire in than buy a new relay each time as i have to order from US and pay shipping,customs etc and it gets quite pricey….i have the wiring diagram to go through but just wondered if anyone had come across this before.

    thanks in advance

  2. #2
    Senior Member supachip1's Avatar
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    answered my own question and just saved $120!!!


    i have seen many posts asking for help when a tw won't start for various reasons….well, a couple of times now on drum brake models i have had all electrics working.. lights, indicators, power everywhere but nothing happens when pressing the start button….both times after checking everything and disconnecting all safety switches it had come down to a faulty black relay…..for me this is expensive and time consuming because i have to order and have the part shipped over…..not any more…for future reference to anyone thats interested or has this issue…you can by-pass the relay easily.

    remove the relay and with a small length of wire bridge the brown and blue/white wires together…the start button will work again bike will start up and won't affect the safety switches.

    thanks

  3. #3
    Senior Member Devils Advocate's Avatar
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    Just so you know what you're doing when you bypass a relay; the relay is a switch, usually a heavy duty switch that needs to have contacts that can handle high current. The relay is engaged by a (usually) magnetic coil that takes less current. What you are doing with the relay bypassed is putting the switch that is designed for a lower current into the circuit that is carrying higher current. It may work fine, for a while, but the switch that is starting the starting motor is not rated for that high a current.
    goldenhtr, Fred and Vishwa Kau like this.

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  5. #4
    Senior Member supachip1's Avatar
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    i understand what you're saying..ish, i don't usually like to bodge things up and have spent hours rewiring, soldering, re-looming the wiring on the TWs i have to put everything back to how it should be and working properly….from what you said how i understand it is…bypassing the relay = higher current going into the start relay= possibly burning out start relay?

    i didnt know how the relays work hence my initial post..i was happy with my fix..now not so!..but at least its working and i can move the bike around and know its something to check next time on a none starting bike….i will add a black relay to the next order i make. thanks for the info

  6. #5
    Senior Member sponge's Avatar
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    Quote Originally Posted by supachip1 View Post
    i understand what you're saying..ish, i don't usually like to bodge things up and have spent hours rewiring, soldering, re-looming the wiring on the TWs i have to put everything back to how it should be and working properly….from what you said how i understand it is…bypassing the relay = higher current going into the start relay= possibly burning out start relay?

    i didnt know how the relays work hence my initial post..i was happy with my fix..now not so!..but at least its working and i can move the bike around and know its something to check next time on a none starting bike….i will add a black relay to the next order i make. thanks for the info
    Post a pic of the relay, often there are a number of cheaper replacements out there. The main issue is that you get one that is rated for the correct currents.
    Running full starter current through the start button will toast it or possibly melt insulation off wires in the harness, leading to all kinds of electrical shorts. Somebody more familiar with TW electrics can chime in about if they all use the same relay.

  7. #6
    Junior Member Dustin's Avatar
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    Bypassing the safety relays ( black relay ) will not run "starter current" through the starter switch. The starter motor is wired to the battery and has its own relay triggered by the starter switch. When the small current runs from the switch it closes the relay on the starter motor and the motor then pulls the power it needs directly from the battery, NOT through the switch from the battery.

    Edit: wait, need to check my bike sober. I may be wrong.
    Last edited by Dustin; 06-26-2015 at 10:41 PM.

  8. #7
    Senior Member sponge's Avatar
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    Ok a quick check of the service manual shows
    tw starting diagram.JPG
    Dustin is correct, unless you are doing a crazy rewire you wont run the starter through the switch. More likely you are bypassing relay #6 whos basic function is to stop you from engaging the starter when you shouldn't. There are two circuits that close this relay and allow you to start the motor.
    1. clutch in + kick stand up. (transmission doesn't matter)
    2. transmission in neutral. (kick stand and clutch don't matter)
    grounding out ether circuit will just remove those requirements and allow the starter to go. This is a safety relay not a high current relay, your wiring and start switch is safe. Bypassing the relay removes both safety circuits but not #7 start switch or #8 engine run switch.
    Last edited by sponge; 06-27-2015 at 01:26 AM.

  9. #8
    Senior Member Dell's Avatar
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    What i did with mine was to get an inexpensive ignition relay and wire it in. They will be in discount auto stores near with electric stuff. I found one i liked tonight that had pigtails and a switch for 8$ at AutoZone. If it has 4 prongs, fine, if 5 the extra one is a ground. I don't think you want a heavy duty one, such as is used for pumps, just a little one that looks like a flasher relay (but I am sure you don't want it to blink!) Flashers will have a rating as to how many lamps they can carry, and relays won't. Likely it will not fit in the holder anymore.
    The colored wiring diagrams pinned show this a bit more clearly as part 16, switching the blue/yellow wire by the brown and red ones. This unit is the one that clicks under your right thigh when you when you the key to the first detent. You can test it off the bike with a volt meter from the low side: only the black and red should have continuity. If it is on the bike, listen for the click when you turn the key, and clean your connections.

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