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Post by Mr Stabby on Apr 13, 2019 13:58:09 GMT
If you don't ride it at night, just cover the lights and switches with masking tape before you take it for MOT.
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Post by Gone on Apr 13, 2019 16:03:18 GMT
I would measure the voltage at the headlamp with the engine running at idle, then increase the revs to a cruising speed and note the voltage. Assuming it is a 6volt system I would expect the voltage to be about 7volts at high rpm or 14 to 14.4 on a 12v system. Much higher than this would explain short life bulbs. If the voltage is too high then check the regulator.
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Post by deadly on Apr 13, 2019 19:30:53 GMT
I concur with Mr Stabby, it's your battery. This is a fault I've experienced on dozens of different bikes over the years (I buy and sell motorbikes), all older ones, the reg/rec won't regulate without a good working battery and it's the smallest bulb filaments that suffer first from over-voltage, the neutral light, high beam warning, and the tail light. Doesn't take out unified indicator warning lamps due to the way they're wired but will take out individual left or right ones.
Currently got a DT175MX doing exactly the same thing, need to get it a new battery and a new neutral lamp before I can hang a price ticket on it.
Only time I've seen this fault not be fixed by a new battery was on an early 1970s Honda C90, selenium rectifier, had done at least 10K miles with no battery at all, toasted the rectifier.
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Post by Clinton Cool on Apr 13, 2019 20:36:19 GMT
I concur with Mr Stabby, it's your battery. This is a fault I've experienced on dozens of different bikes over the years (I buy and sell motorbikes), all older ones, the reg/rec won't regulate without a good working battery and it's the smallest bulb filaments that suffer first from over-voltage, the neutral light, high beam warning, and the tail light. Doesn't take out unified indicator warning lamps due to the way they're wired but will take out individual left or right ones. Currently got a DT175MX doing exactly the same thing, need to get it a new battery and a new neutral lamp before I can hang a price ticket on it. Only time I've seen this fault not be fixed by a new battery was on an early 1970s Honda C90, selenium rectifier, had done at least 10K miles with no battery at all, toasted the rectifier. That's really interesting. The rear light, indicators, headlight sidelight, oil level warning light, neutral light are all on bulbs that were in the bike when I bought it, 2 years and 4000 miles ago. The backlight for the speedo and rev counter were blown when I bought it. I replaced them, they both blew again shortly afterwards. I haven't bothered replacing them. The headlight bulb that was in the bike lasted for 6 months before it blew, none of the replacements have last for more than 100 miles, sometimes they blow within a mile. I replaced the battery with a brand new one when I bought the bike. It's a Yamaha RS125DX 1982, 6v electrics. There's no voltage regulator, just a rectifier. My understanding is this just converts the AC current generated into DC. Does this throw any more light on it? Incidentally, as you mention the DT175MX the 125 version of this bike saved me a lot of bother. The needle in the carb and its housing were worn on my bike. It was sticking. Sometimes open, sometimes closed. Hell of a job to find a replacement. Eventually found one in America but it was £££s. Someone told me the DT125MX shared the same carb, ordered the rebuild kit for a tenner, sorted! By the way I have a small crack at the top of the left hand bottom fork leg. It's held together by a jubilee clip, weeps a tiny bit of oil. No problem at last MOT but I'd like to fix it really. Can't find a replacement anywhere, any ideas? Or might it be possible for it to be repaired, welding of some type?
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Post by Telemachus on Apr 13, 2019 21:36:25 GMT
Not sure about your specific bike but some early jap bikes didn’t have a regulator. They did have 2 tappings on the alternator such that when the headlight was off, the tapping for low alternator output was connected. When the headlight was put on, the switch also brought into circuit the higher output tapping in order to supply the load for the headlight. The battery took any excess charge.
So maybe your battery connections (to the electrical distribution circuits) are poor, high resistance. Maybe the high alternator output tapping is permanently in circuit due to a switch or wiring issue. Maybe you have the headlight on with bulb blown or wrong wattage.
But anyway, as a first step and as said already, you need to measure the system voltage (not the battery voltage) with the engine running at mid-range revs and with the headlight on and off.
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Post by Clinton Cool on Apr 13, 2019 22:58:27 GMT
Cheers for that Nick, a project for the next couple of days. That's if I can somehow hold the probes from the meter on the tiny contacts in the headlight locator, whilst my third hand gives it a few revs. I can feel a proper Heath Robinson affair coming up, could involve a length of string or maybe an improvised clamp around the throttle, maybe attached to a broom pole or similar, with onlookers walking past with bemused looks, due to my strange leg movements.
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Post by Telemachus on Apr 13, 2019 23:11:52 GMT
Cheers for that Nick, a project for the next couple of days. That's if I can somehow hold the probes from the meter on the tiny contacts in the headlight locator, whilst my third hand gives it a few revs. I can feel a proper Heath Robinson affair coming up, could involve a length of string or maybe an improvised clamp around the throttle, maybe attached to a broom pole or similar, with onlookers walking past with bemused looks, due to my strange leg movements. You can usually poke the probes into the back of an appropriate multipin connector thus freeing up your hands.
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Post by Deleted on Apr 14, 2019 7:51:37 GMT
Cheers for that Nick, a project for the next couple of days. That's if I can somehow hold the probes from the meter on the tiny contacts in the headlight locator, whilst my third hand gives it a few revs. I can feel a proper Heath Robinson affair coming up, could involve a length of string or maybe an improvised clamp around the throttle, maybe attached to a broom pole or similar, with onlookers walking past with bemused looks, due to my strange leg movements. ^ Too much information Ricco, but I like it . . 'I have a small crack at the top of the left hand bottom fork leg.' . . There is stuff called JDWELD or some such. [for your cutlery]
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Post by Jim on Apr 14, 2019 9:06:11 GMT
Cheers for that Nick, a project for the next couple of days. That's if I can somehow hold the probes from the meter on the tiny contacts in the headlight locator, whilst my third hand gives it a few revs. I can feel a proper Heath Robinson affair coming up, could involve a length of string or maybe an improvised clamp around the throttle, maybe attached to a broom pole or similar, with onlookers walking past with bemused looks, due to my strange leg movements. ^ Too much information Ricco, but I like it . . 'I have a small crack at the top of the left hand bottom fork leg.' . . There is stuff called JDWELD or some such. [for your cutlery] I've used that, to glue new exhaust pipe studs into the cylinder head of a suzy 400. It's a high strength slow setting epoxy resin. possibly JBweld.
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Post by Clinton Cool on Apr 14, 2019 9:27:44 GMT
I've used it (JD, JB, can't remember) to plug a hole in the crankcase cover I stupidly caused by kicking the bike over with the footrests removed. The footrests stop the kickstart lever hitting the crankcase cover. This, along with a small phillips head screw sized to fit the hole, with the screw bit chopped off, has served well, and is oil tight. Can't see this working with the fork though, it's a precision job. Might give it a go though.
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Post by Jim on Apr 14, 2019 11:01:18 GMT
If its a hairline crack, then if you could clean it out with carburettor cleaner or similar, superglue would work. I bought a kit, superglue and powdered glass, for open holes, fill with powder and flood with superglue.
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Post by Clinton Cool on Apr 14, 2019 11:07:04 GMT
Cheers Jim I'll look into this.
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Post by Clinton Cool on Apr 16, 2019 17:01:17 GMT
I've been playing around with my multimeter. The battery voltage rested for 24 hours, was 6.35. Seems OK?
I checked all the light fittings with the engine running. At 2000 rpm the reading was around 7.5v. At 5000 rpm it was closer to 8v. Would I be right in thinking this is a bit high? The voltage readings were very similar at all the light fittings. Might this suggest that the headlight bulbs are indeed crap? none of the others have blown. Otherwise, if the voltage is too high how might I reduce it? The rectifier is described as exactly this, rather than a rectifier/ regulator.
Any thoughts?
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Post by Telemachus on Apr 16, 2019 18:44:50 GMT
Yes 8v is too high and will cause bulbs to have very short life. But you don’t mention whether this was with a functioning headlight bulb switched on, or with the headlight switched on but not working due to filament blown, or headlight switched off.
If the first then probably the wattage of the bulb is too low (it is not loading the electrical system enough). Have you checked that you are using the bulb wattage as specified in the manual / bike specifications, as opposed to replacing the bulb with a bulb of the wattage that happened to be fitted to the bike when you bought it?
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Post by Clinton Cool on Apr 16, 2019 20:19:23 GMT
Yes 8v is too high and will cause bulbs to have very short life. But you don’t mention whether this was with a functioning headlight bulb switched on, or with the headlight switched on but not working due to filament blown, or headlight switched off. If the first then probably the wattage of the bulb is too low (it is not loading the electrical system enough). Have you checked that you are using the bulb wattage as specified in the manual / bike specifications, as opposed to replacing the bulb with a bulb of the wattage that happened to be fitted to the bike when you bought it? I took the voltage readings at all the bulb fittings by removing the bulbs, putting the positive probe on the fitting, and the negative to the frame. Bulb when I bought is was 25w/25w. Replaced a few of these then after reading the manual more carefully realised the spec was 35w/35w. Bought a box of 10 of these, only 3 left now!
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