help with rectifier/ electrickery

Justin350 · Post by **Justin350** » Fri Jun 24, 2011 5:08 pm

Can any one give me some pointers as to what may be the problem with my '61 8M?

I have recently replaced the rectifier and battery BUT. . . recently the electrics short circuted due to improper insulation there was much smoke.
any how, i replaced the cable wich was melted and since then the charging has been poor at best until yesturday i was coming home, much spluttering and eventually it packed up completely (1 mile from home and one big hill)

there is a weak spark and some blistering on the rectifier (from the aformentioned mis-hap), could this be the issue? i would have thought that it would run irrespective of battery state.

also, can any one tell me whether the solid state rectifier on the jampot website will be a viable replacement as i have a plate rectifier presently.

many thanks.Edited by - Justin350 on 24 Jun 2011 4:51:41 PM

Tolly · Post by **Tolly** » Fri Jun 24, 2011 10:06 pm

If it's not giving a charge and the battery goes flat it will splutter and eventually cut out.
If I were you I would contact Colin Farrington, Tel: 01603 737702, who is on this forum at times and advertises in the Jampot mag, and ask him to make up a new wiring loom,it's not worth trying to repair yours if you've had a wire burnt. While you're at it convert to 12 volts, it's well worth the effort. You will need a solid state rectifier if you go down the 12v route, I'm sure Colin will be able to advise you.

Hope this helps.

Justin350 · Post by **Justin350** » Sun Jun 26, 2011 10:13 pm

nice one, thanks . . . the 12 volt conversion is certainly on the cards but being a student i'm a tad skint. i think a new rectifier will do the job for the forseeable future. many thanks.

SPRIDDLER · Post by **SPRIDDLER** » Sun Jun 26, 2011 11:44 pm

If one wire has melted chances are it's not the only one so fit a fuse in the main battery feed of a size (ampere rating) that will blow before the wiring melts again!
Not sure about G5/Model 8 electrics but try a 10 amp to start with - it may be enough. If it blows, go up to a 15 amp max.
Some may say higher, fine if they do, but a 10 amp fuse will support a 60 watt demand on a 6 volts system and a 15 amp, 90 watts. Surely enough?
To check, add up the power (wattage) of your headlight main beam, tail light and stop light, plus your speedo light plus the ignition circuit (don't know what that is as I'm a mag ignition user), then divide the total by 6 (your system voltage) and that will tell you the minimum size of fuse needed.

en7jos · Post by **en7jos** » Mon Jun 27, 2011 1:00 am

As per Spriddler's remarks - FIT A FUSE!!!!

To decide on an appropriate amp rating, add up the various electrical components as per Spriddler's list, but you will also need to add on a bit of a safety margin. The resistance of the filaments in bulbs are initially low (for a second or so) when they're first turned on, and hence the current has an initially rush before it settles down to the rating stamped on the bulb. I'd start with about a 50% safety margin (i.e. multiply your total bulb etc wattages by 1.5), but this will obviously depend upon fuse rating availability and probably some trial and error.

Either way, start with a lower rating and go up if you find it blows in normal operation.

If one wire has fried, chances are others are damaged too. Same goes if one was susceptible to short-circuiting as you described. A new loom seems a very sensible place to start!

James

Justin350 · Post by **Justin350** » Tue Jun 28, 2011 9:50 pm

thanks fellas, i have a few 10 amp fuses left over from my ahem*yamaha so one of those should fit the bill. i'm taking the oppertunity to fit some rather nifty bar end indicators too.

thanks again a fuse is going in in about 5 mins.

wilko · Post by **wilko** » Wed Jun 29, 2011 12:55 am

Those little square rectifiers from radioshack do the job for 2 bob!

SPRIDDLER · Post by **SPRIDDLER** » Wed Jun 29, 2011 10:40 am

Good move, but I believe the indicator lamps could be about 20 watts each, so when winking fore and aft there'll be an extra 40 watt (6.5 amps) surge. They may wink very slowly or not at all.
You may find the 10amp fuse blows when you indicate when running with lights on, and it'll test the battery condition, especially if you've been toddling around at urban speeds which would not be fast enough to keep the battery charged.

Later
Ah, just realised you're fitting new-fangled 'bar-end' indicators in which case I assume you have fore and aft ones already which are working so you may be o.k.
Don't try fitting heated grips though Edited by - SPRIDDLER on 29 Jun 2011 1:25:07 PM

Justin350 · Post by **Justin350** » Mon Jul 04, 2011 10:14 pm

hmm, new rectifier has gone in and, you'll never guess what . . . still no charging. not only that but now it seems that i have developed an intermittent fault so there no ignition at all now.

a new loom is certainly in order.

jimbob · Post by **jimbob** » Tue Jul 05, 2011 5:11 pm

Might be an obvious point but I would try checking the earth on the rectifier.