AJS & Matchless Owners Club

Hi, yes, wiring and gaskets...a few questions..
Went to start the bike recently and became aware of the smell of burning with accompanying smoke issuing from beneath the fuel tank. Removing the tank disclosed a fried lead to the horn. Do you think it best to rewire completely or is this overkill? Why didn't the fuse work?!
I've decided while I'm at it to sort a leaking base gasket and a smokey cylinder. Is a copper gasket a better seal than composite (and doesn't need retorquing?)? And should I go for a thick or thin base gasket?
Cheers,
Harvey.

I would rewire. If the wiring has decayed enough to short out then patching it up wouldn't be best. It's not too tricky a job.

Harveykynaston wrote: ↑Thu Nov 02, 2023 3:41 pm Why didn't the fuse work?!

Where is the fuse fitted and what is its current rating? With the factory loom the hooter and the stop light are wired unfused direct to the battery.
(As far as I'm aware the factory never fitted fuses at all to any of the bikes).

See the wiring dia. on page 86 in the Owners Manual here:

http://archives.jampot.dk/book/Owners_m ... Models.pdf

I go for the thicker barrell base gaskets myself but its personal choice. Is it a magneto (Deluxe) or an alternator model (standard)? The magneto/dynamo models are easy to re-wire but the alternator models are a bit more complicated. I would definately fit a fuse. Is it 6 or 12 volt?
I would first investigate thoroughly the reason for the wire burning out.
Dave.

SPRIDDLER wrote: ↑Thu Nov 02, 2023 6:21 pm

Harveykynaston wrote: ↑Thu Nov 02, 2023 3:41 pm Why didn't the fuse work?!

Where is the fuse fitted and what is its current rating? With the factory loom the hooter and the stop light are wired unfused direct to the battery.
(As far as I'm aware the factory never fitted fuses at all to any of the bikes).

The slow blow fuse did work, it is called the wiring loom. We don't call Mr Lucas the Prince of Darkness for nothing.

I would replace it, as you can either buy a new loom or do what I did and make a new one. I upgraded the wire size to get extra oomph out of the woeful 6V electrics. You could have an issue with the horn but I suspect the wiring in general is well past its best-before date. I know with mine that just applying the rear brake acted as a kill switch, wires near the light were shorting out on stuff.

Many thanks for your help all. In answer to a few queries raised: the machine is a coil/alternator model and converted to 12v with two of those small sealed (lithium?) batteries connected to each other. May be they are part of the reason why everything got very hot very quickly, I've heard they discharge much quicker than lead acid but I'm a dunce so that might be rubbish. I can't remember what fuse it had, it was fried too and I threw it away.
I've decided to have it rewired. I note what was said about it being more complex than a mag model but it's plainly the right course of action although beyond my capability, as I've mentioned in previous missives, electrical matters are witchcraft to me.
RE the gaskets, I'm leaning towards a thick one (should say "ones", I'll do both), in the possibly mistaken belief that it may provide a better seal but I'm still undecided about a copper or composite head gasket.
Oh, just an aside, just in case you read my woes about my dead M20 earlier this summer where I had electronic ignition fitted...twice because 16+ volts were coursing through its veins, so replaced the rectifier/regulator but still without success until the fuel starvation issue was sorted....it FINALLY starts and runs like a watch. So It back in love with it again and won't have a word said against it!
Anyway, I've gone on too long. Thank you again for replying, I think it's great that people not only take the trouble to read but also help fellow club members. And up here in woolyback land (aka NW Shropshire) I don't get to meet many so if anyone is ever around Oswestry/Welshpool, the kettle is always on....and I have a workshop with spanners! Cheers, Harvey Kynaston.

The alternator wiring diagram can be made much simpler on 12 volts using a reg/rec. I can't think why a sealed battery would make any difference. I've been using them for years with my own simplified diagram, electronic ignition, reg/rec and LED lights etc. Nice part of the country you live in. We (NW section) have had several 5 day trips to Welshpool and Rhayader. Some great rides.
Dave.

As far as head gaskets go, I have composite ones on my M31 and they've worked well, but I was very careful with the torqueing and re-torqueing down sequence. If you go for copper, anneal them well, and don't forget the 4 viton O rings for the oilways.
My bike is fitted with indicators, and I have separate fuses for them and for the main wiring loom, using mini blade type fuses. I have bought, but not yet fitted, a small fuse box so I can tidy it up a bit and also fit a couple more fuses for the rear brake light and the horn. It's a dynamo model fitted with a DVR2 voltage regulator.

Malc