1973 T140 Troubleshooting Advice

You've said there's no spark and it wont turn over. Are you saying you can't kick it over? Or do you mean it doesn't fire when you kick it over?
Have you taken the sparkplugs out and checked for a spark when you kick it over?
There's a fuse in the picture by the left hand coil, have you checked that?
I doubt it's a flooding problem. It sounds like a simple electrical grounding/connection issue.
Talk us through what you've done, we'll get it sorted between us. It'll be fine.

 

Oh, and by the way, welcome in. Experts in here @speedrattle @darkman will be along shortly to help. Once we get your starting issue sorted you'll need to go say hello in the 'newbies' section.

 

Electrics have never been my strong point :-(

 

i are not an xpert

good advicr here already

but if you dont have a spark but do have the idiot light on the headlamp shell then your ignition switch and fuse appear to be working.

your kill switch works by means of a couple of springs holding the button up. is the kill switch button loose?

does this bike have points or an electronic ignition? the points could be burned.

i suggest you take a wire and jump from thr negative post on tje battery to the negative lead on each coil to hot wire the bike by bypassing the key, kill switch, fusr and all connectors in the harness. see if it sparks then

if you have a loose connector in a white wire circuit in the wiring harness feeding the ignition it will jiggle around and cause misfires and then kill the motor when it finally pulls out far enough. it can do this while appearing to be plugged in. so check all connectors

 

Not mine either which is why I asked for help

 

sounds quite 'experty' to me,

 

I can see a Boyer ignition box so assume it has EI fitted

 

so it has. id been driving for 22 hours snd was not observant

anyway the boyer makes it easier to check. power goes into the boyer transistor box through the white wire. unplug that wire from the harness and run a jumper from battery negative to the white wire. everything upstream from the boyer box will be disconnected, so if you still dont have spark it will be tje boyer box, the coils, the secondary plug wires, or the spark plugs.

check the boyers connection- black, white, and red wires. check tje two wires leading to the stator in the old points cavity.

i once had a boyer stator melt its epoxy in the points cavity and stop working. take a look.


if you still dont get a spark after hotwiring the boyer box, do the scratch test. leave the boyer box hot wired and unplug the black white and black yellow wires from tbe stator in the points box, or finds their ends somehow. scratch the bare ends together. if tbe plugs suddenly spark the box is good and tbe problem is the stator or downstream wires connections, plug wires or plugs.

if there is no spark, be double sure by briefly unplugging power to the boyer box and plugit back in. within thirty seconds do the sctratch test again. if it still wont spark the problem is probsbly in the boyer box. you have to double check this way because a boyer box will turn itself off if it gets power but the engine isnt kicked within 30 seconds. they did this to keep the coils from overheating if you forget to turn the key off. its why you often must kick s boyer bike twice to start it if youve left the key on at tbe petrol station. unless you have gods own foot and kick hard enough to make the motor go round teice


do this stuff and tell us ehat you discover

 

Very good considering you ain't an expert. Lol

 

Robert N
Welcome to the family. Hope you get it sorted. I have an 80 ex and it blacks the plugs up after a few miles no mater what i try. Waiting for new carbs to see if it sorts things out. The Amal's on there have been sonically cleaned reset a million times chokes replaced for cable chokes and it goes on. But i will get it eventually one little bit at a time.
Joe.

 

i forgot. are those the original 12volt ignition coils? because boyers work best with nominal 4 or 6-volt coils.

boyer recommends coils having a total resistance of 3 to 4.5 ohms. two twelve volt coils can run up to 8 ohms wired in series like the boyer requires, but others can be found with lower resistance.

i have a machine running two dynatek coils and a boyer. each coil runs 2.2 ohms, so th ecombined resistance is 4.4. within their recommendations.

you running your boyer with the original coils might be part of the problem. if it is, you could solve the problem bu buying a single dual-outlet coil with an internal; resistance of 3 to 4.5 ohms, or two sngle outlet coils of around 1.5-plus each.

you need at least 3.5 ohms combined or the transistor box will overheat.

your motorcycle looks like its in very good condition, btw

 

Robert, did you fix it? Have you fallen over?

 

Hi to all! really hope that somone like @speedrattle @Iron can help me too! I bought also a Bonnie 1973 and I can ride it for a while, yesterday I could not start it. The electrics keep blowing the fues. The engine was rebuilt, spark plugs are ok and battery too.. Maybe there is a wire broken and touching the frame or something metal and blowing the fues?

 

Its a good chance that a wire or connector in the headlight shell is shorting out or like you say a bare wire touching the frame, if you get stuck i'm in Bournemouth and could have a look.

 

That'd be great! Thank you so much

 

Yep, sounds like a grounding wire somewhere.
Do the fuses blow when you use something like indicators or lights or handlebar switches? Put in a new fuse, switch on and try all the switches, one at a time. The culprit wiring will blow the fuse.
Visually check where wires are exposed or could rub. Check under the tank.
Look under the seat, make sure no wires are getting flattened or that the seat base touching the battery terminals when you sit on it.
Inspect the wiring around the headstock for rubbing/wearing and check the switchgear wiring on the handlebars just unscrew and check the wires are not squashed.
I'd expect the bad one to be fairly obvious when you find it. It could have melted insulation near it. After that you'll be into checking the individual circuits with a testmeter. Elimination, one by one from the wiring diagram checking if each wire is making a circuit with the frame.
Put your thinkling cap on and take your time, best of luck, and let us know how you get on.....

 

Thank you, I will let you know!

 

Now that is a new word @Iron