Finished the wiring on the 1940 M20. Just have to let in a stop light switch when I get it. Battery coming early in the week. As all know there are no fuses in the system so if something shorts out then the lot goes up in smoke including the seemingly unobtainable head light bulb with dip filament. Is it right and safer to fit some in line fuses. If so where is it suggested these be added?
I did the timing again, runs better but still backfiring on the overrun, when throttle is released. I am getting the hang of it but confirm that there is no margin for error and that it must be set correctly or it will not run right.

email (option): araine11@hotmail.com

Hi Arthur,

I fitted only 1 fuse, on the battery positive side,
And it did burn few times, maybe saving the system.

(Last Saturday I went for some 90km ride with the classic bike club,
mainly Hondas from the 70, A Triumph Thunderbird 6T and my WM20..)

I took the sidecar off for the ride, and did not isolate the lead to the sidecar lamp.

It touched the body and the fuse burnt.
I use 10 Amp fuse for 12V system.
For 6V, I would use 15 Amp, as theoretically 10 Amp is the max charge,
and with full headlights, break light and horn,
you would be around 11 Amp.

Noam.

email (option): noam10@gmail.com

A fuse on the battery +ve is a must. This can be hidden inside the dummy battery box if you're using one. I have mine outside as I like to have everything electrical easy to disconnect when the machine is unattended.

Backfiring on the over-run sounds to me like an air leak on the inlet side.

I agree Rik,

Mine is under the fuel tank, next and behind to the left fuel tap.

It is not visible, unless you look at the area from the tap height,
And it is easy to access without any tools.

Noam.

email (option): noam10@gmail.com

thanks for that. I will get one on Monday

email (option): araine11@hotmail.com

Only girls use fuses Be a man and don't use one.

My Norton single kept blowing its fuse. I traced the dead short to the bulb holder in the illuminated chrono speedo. Without the 15 amp fuse that Id fitted things could have ended badly.
Fit a fuse

I have 10 amp fuse in the battery box. Never burned.

Backfiring on the over run with an M20 is more likely to be an air leak around the exhaust pipe where it fits to the barrel...Unburnt fuel then ignites in the exhaust..Pretty common with the M20 as the barrels and pipes get worn/distorted...
Fit a fuse...It can be expensive not to...You won't look very 'Manly' with your bike on fire at the side of the road.. ....Ian

email (option): ian@wright52.plus.com