Square 4 wiring problems

[PHILLIP LAWTON]

can anyone offer advice on a wiring problem on my first post?
The bikes a 1958 MK11 Square 4, rewired by Draganfly two years ago ( still 6v) and has a Boyer Mk 111 Ignition system.Unfortunately they didn't fit an inline fuse and while riding it suddenly lost power and the plastic covering on the Negative lead from the battery to the loom and one of the wires on the Negative side of the Ammeter melted, as did the Ammeter .(photo's are available if it helps)

I've fitted a new loom from Draganfly (with a 10A inline fuse ) and a new Ammeter, with the Boyer unit wired as before.

All lights inc brake light and horn work but turning on the ignition 'results in a blown fuse.

The wiring connections have been checked several times. individual test cables have been run from the battery to the ignition switch and from the switch to the Boyer unit but the problem persists.

I have no idea what caused the original meltdown ,but was wondering if the regulator might be at fault.

Any help appreciated.

Phil ..in snowy.Finland

[simon.holyfield]

Do you have a wiring diagram? There is one here:

http://ariel-square-four.blogspot.co.uk ... iring.html

[Bob.Murphy]

Is a 10A fuse high enough ??

That's only 60 Watts. An ignition coil will draw a higher current when static than it will when the engine is running and the Control Unit will also draw something. Does the Boyer instruction book give any clues as to the static load??

Did you find the cause of the original melt-down ??

My first step would be to test the resistance of your ignition coil and then do a continuity check on the rest of the harness.

Let us know what you find.

Welcome to the site by the way .

Bob.

[nevhunter]

Your horn normally doesn't go through the fuse or the ammeter. You must have something somewhere earthing out. (10 A is not enough) . Earthing out suspects are stop switch, horn, Headlamp switch. then sockets for various bulbs. Isolate sections of the services and ride it and by a process of elimination exclude each section of the wiring. Have fuses handy or cheaper, some strands of thin wire till you get it sorted. Check current drain for each unit and have about 50% above for fuse or weak link wire used as protection of you wiring. Nev

[jerry.mortimore]

If you have a nacelle with instrument panel, make sure the light switch connections are not shorting to the top yoke. That happened to me many years ago and it exploded the switch and melted the insulation on several wires.

[PHILLIP LAWTON]

Thanks for the replies,will attempt to sort it this weekend
Rgds

[PHILLIP LAWTON]

hello Gents,
Increased the fuse size to 25A ,isolated problem to the ignition side of the wiring loom and finally traced the problem to the ignition switch which had shorted out internally.

rgds

[greg.geonetta]

Simes

I'm planning on using your wiring diagram for my bike ('51 SQ4) and had a few questions.

Is your diagram negative ground? I'd like to have neg ground for my bike.

You show unswitched power going directly through the ammeter, would this not result in a draw on the battery when the bike is not running?

Lastly, the headlight mounted switch on my bike is apparently different than the one you show, mine has 7 contacts total but 3 are not used. The switch has only 3 positions, OFF, L (low), and H (high). The switch you show looks like it must have 5 positions?

Thanks

Greg in Arizona

[nevhunter]

The ammeter is an in series instrument with no ground. The horn circuit is usually excluded from the ammeter but all other users are sensed when the switch connects them to the supply. Nev

[iansoady]

Stop light is usually on the same side as the horn so doesn't show a discharge when operated.