Batteryless norton commando 750 cafe racer

S

Shadowcat

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Aug 1, 2021
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Hi there,Currently have just purchased a 73 norton Commando complete with period cafe racer goodies.Previous owner has converted it to batteryless spec.Bike I believe has never run.My question is what would I need to do to it at a bare minimum to get the bike running.
It currently has boyer ignition in addition to a boyer power box.Putting a battery in now is a no go,as battery space is now filled with the horn and a one position ignition switch.Certainly don't mind spending what ever it takes to get the bike running smoothly and reliable.Need to get the thing started so I can move on to whatever works on the electrics.
 
Does it have the 2MC emergency starting capacitor (blue can below) as that should allow the bike to run without a battery however that may only work with original points ignition but might not work with electronic ignition.
Batteryless norton commando 750 cafe racer
 
I don't think a Boyer will run off the alternator (I could be wrong) so I think you'd need to fit a battery.
 

​

Power Box​

Power Box and Dynamo Regulator
"The power box is a self regulating rectifier with an internal current and voltage storing capacitor."
 
The Boyer powerbox has an internal capacitor to allow batteryless running, but the capacitor is the weak link and fails with age but the rest of the box should still function with a battery.

Boyer Power Box

Alternator Regulator Single Phase 12 Volt.

When building a Desert Racer, this is what we use when replacing the battery. Tried, tested and recommended by us!

  • Controls charge rate
  • Rectifies from AC to DC
  • Can be used without a battery due to capacitor
  • Easy to fit with only 4 wires
Best suited to use for a bike with no lights.

These Power boxes can be used on a bike with lights, but please be aware the lights will dim on tick over. To maintain a constant light we recommenced fitting a battery alongside the Power Box.

Warning: When the Power Box is fitted with no battery, the lights must be on a switch and the switch turned off when starting.
 
kommando said:
The Boyer powerbox has an internal capacitor to allow batteryless running, but the capacitor is the weak link and fails with age but the rest of the box should still function with a battery.

Boyer Power Box

Alternator Regulator Single Phase 12 Volt.

When building a Desert Racer, this is what we use when replacing the battery. Tried, tested and recommended by us!

  • Controls charge rate
  • Rectifies from AC to DC
  • Can be used without a battery due to capacitor
  • Easy to fit with only 4 wires
Best suited to use for a bike with no lights.

These Power boxes can be used on a bike with lights, but please be aware the lights will dim on tick over. To maintain a constant light we recommenced fitting a battery alongside the Power Box.

Warning: When the Power Box is fitted with no battery, the lights must be on a switch and the switch turned off when starting.
Click to expand...
The ignition switch has been resited to the front of the battery box(no battery fitted),along with the horn.The ignition switch is a single position on/off.From what I can see there appears to be no seperate light switch.Unless the handlebar switches are serving this purpose perhaps.But until I get the beast running I cannot check the lighting.BTW no indicators.
 
Can you get any sparks with the plugs out?
You can disconnect the headlamp and tail lamp easily enough just by removing the bulbs temporarily or just unplug the headlamp assembly.
 
My commando would run on a Boyer MK3 with a 2mc capacitor if you started it with a battery connected first
My t140e would run without a battery from memory but it was a pig to start
 
My experience of the powerbox and Boyer ignition on a norton twin without a battery is that the output is marginal for *easy* starting and idle. An order of magnitude harder if you have lights on!

On my 650 and 750 I ended up putting a small (screwfix, house alarm) battery on both.

Just enough to help starting and a slow idle with lights on etc.

My advice would be to go to first principles without lights or switchgear. Wire the alternator to the powerbox and thence to the Boyer. With plugs out, ensure you have sparks.

Then check the timing of the Boyer.

If all good, with fuel, in this state, it should run.

Good luck!
Andy
 
If you want to go fully batteryless then spend the money and install a Joe Hunt magneto and problem solved and run your lights straight off the ALT using a battery eliminator regulator, might even work with a Boyer, I went straight from a Boyer EI to the Joe Hunt and was the best thing I ever done to my Norton going to a JH magneto.
 
ashman said:
If you want to go fully batteryless then spend the money and install a Joe Hunt magneto and problem solved and run your lights straight off the ALT using a battery eliminator regulator, might even work with a Boyer, I went straight from a Boyer EI to the Joe Hunt and was the best thing I ever done to my Norton going to a JH magneto.
Click to expand...
Ash is feeling better! 👍
 

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