QT50 wiring newbie - lights and kill switch

Dear All,

I am a brand new owner of a 1980 QT50 - It is mechanically running fine, but has some electrical problems I am trying to address. Problem is that I am a complete newbie to wiring u a vehicle. I can follow instructions, but have very limited experience figuring out what am I actually looking at.

The things I am looking to address are:

1) the left brake lever is not connected to the brake light cables. The brake operates but the light does not light up. It seems I need a clip at the end of one of the wires and plug it in. Correct?


2) the engine kill switch is missing. I have the wire in there, but no switch. Any advice what switch I need to get? Can I get a switch or do I need the whole assembly?


3) The turn signals are not blinking. The proper light light up, but stay lit. I have t turn it on and off to simulate blinking. Is this a common problem? Is this a relay? wire The manual provides shorthand for checks, but that did not quite get e anywhere.

Thanks .. and I know I am duping a lot of problems at once and have no experience. I am hoping I can earn how to work on my bike independently.

Re: QT50 wiring newbie - lights and kill switch

you can use any switch for a kill switch, looks like all it needs to do is ground that wire there to kill the bike.

the brake thing is pretty simple, it's an on/off setup. Basically you just need to wire that switch in series with the brake light wires

if the winker lights stay on, most likely its the thermal flasher unit. you'll need a new one but make sure it's 6v. also sometimes if the wires get dirty or corroded it doesnt get enough power to trigger the switch to blink.

in all honesty, non of these are problems i'd even worry about at all. I figure as long as the headlight and taillight work and the bike runs good, it's all good to go.

Re: QT50 wiring newbie - lights and kill switch

^in most states you need a brake light, you can hand signal for stop, but no one knows what it means! There is a flasher unit for the blinkers, it lives up front under the horn cover. If there is not enough power though it will not flash. Or it it is fried it will not flash. I know how you feel man, I have an '80qt, runs very well, but no tail/brake light, previous owner had them working, but when I got the bike bulb was blown out, replaced it and nothing...my wireing is janky as hell in and around the battery area, so I assume a short has developed. Directional signals have never worked, I replaced my flasher unit to no avail. Hand signaling is leagal for turns, but I like blinkers, especially at night. My headlamp is bright as hell though. My Batt is fried and disconected, many run these bikes without a batt, so don't think that is an issue, but over the winter I' am going to replace it, 20.00 at batteries plus! I see lots of corossion on the exposed contacts, so will be cleaning that all up, these bikes produce low levels of current so I' am thinking any corroision is draining away voltage. I downloaded the service manual, but wire diagrams give me a headache! I want my blinkers, but would be happy with just a tail lamp and a brake lamp. The guy I got the machine from is an excelent moped mechanic, the bike I traded him for this one had sat dead in my living room for years and in one season he has it modded and blasting, I think the fault lies with Yamaha's wireing, especially after years of exposure to the elements. I know he would have not ridden it with no rear lighting, so it had to have developed a short, otherwise the bulb in it when I got it would not have had blown filiments. There are tons of postings regarding qt-50 lighting issues. One thing I have heard is if the key switch has been messed with it can affect the distribution of the meager current available. My key switch does not kill the engine, but my kill switch does. Look on the buy sell forum for parts, people are always parting out these bikes. Best of luck!

Re: QT50 wiring newbie - lights and kill switch

Thanks for the responses

1) The kill switch really is as simple as grounding it - I had a small piece of it exposed and it touched the chassis - et voila - engine killed. Took me a minute to figure that one out :)

2) I am watching an auction for the relay - I suspected that could be a reason, and if i can get that part for $20 or so - I will buy it.

I have to ass inspection soon, so I want to make sure I do - hence the worry about the electrical gremlins.

Today, I bought a new battery (just in case, $20 at Battery Plus), and a new spark plug - just to find out I do not have a plug socket (fail).

Then took the bike out for a joy ride and it started running rough and then stalled solid. I cleaned it and messed with some part of it = but apparently messed something up .... just another day in getting it solid :)

Thanks for the advice . with the pointers, even the wiring diagrams are making a little bit more sense :)

Re: QT50 wiring newbie - lights and kill switch

Make sure it has oil and that the injector is working.

Re: QT50 wiring newbie - lights and kill switch

Ugh .. cannot get the oil cap off :( dangit ... .. ah well. off to the shop .. it needs brakes anyways :)

Re: QT50 wiring newbie - lights and kill switch

anyone has used this flasher relay?


Does the explanation make sense? for $11 it cannot hurt as long as it works for this model ...

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