DT 125 MX 1979 will not spark

[Dorset Flyer]

I am restoring a 1979 Yamaha DT 125 MX, with 6v electrics and points ignition. I have replaced everything in the ignition system but cant get a spark. I can see volts going to the ignition coil, but no spark coming out!. I've now tried 3 ignition coils, 2 sets of points 3 condensers, and 2 ignition generator coils all with the same result.

Any advice gratefully received I am at my wits end!!!

[Nick the wanderer]

Hi,

I'm pretty sure someone on here knows a bit about these bikes and will help you out. 

 

[Simon Davey]

Hi @Dorset Flyer I had one back in the day, bought it new, never had to touch it, so I know nothing.

But..... have you replaced the HT lead? Or maybe just cut the end and re-attach to the plug cap, as it could be corroded.

What about a spark at the points? Get a jacket over your head and crouch at the side of the bike to check there's a spark at the points for sure.

[Tinkicker]

1. Have you cleaned the protective coating off the point contacts?.

 

2. Connect the black wire from your stator directly to the ignition coil.  This will bypass any faulty switches.

Edited November 17, 2024 by Tinkicker

[Dorset Flyer]

Thanks for the responses, I have run a connectivity test on the low tension lead to the coil and can see the points opening and closing, have now tried 3 coils 3 HT leads and 2 plug caps.

The black wire from the magneto runs directly to the ignition coil.

Very very confused!!!!

[Tinkicker]

Disconnect the black and white wire from the coil and try again.

 

Ensure that you are not using a resistor type plug in a resistor type cap.  It will not work.

 

As mentioned previously.. You did sandpaper the points contacts before fitting them?

Edited November 20, 2024 by Tinkicker

[Dorset Flyer]

Thanks, problem solved, the generating coil that Wemoto supply is incorrect for the Bike, a local mechanic noticed this and had an old original coil that when fitted worked a treat.

 

Happy days.

[Simon Davey]

1 hour ago, Dorset Flyer said:

Thanks, problem solved, the generating coil that Wemoto supply is incorrect for the Bike, a local mechanic noticed this and had an old original coil that when fitted worked a treat.

 

Happy days.

 

You should either marry, or kidnap that mechanic.....