BSA ROCKET 3 starter motor

[iansoady]

I tried that in one of my earlier experiments. Unfortunately they don't output a fixed voltage but only one proportionate to the input voltage. Or at least the one I tried was like that.

[limeyrob]

Thanks for letting me know, I was looking at them for another project.  I think you've just saved me some time and frustration!
Actually it may be relevant to the starter.  I have an old Land Rover converted to a camper and it has a Webasto diesel heater.  These are set to lock out at 10.5 V but for years I've been having lock out problems.  I got the software and ran live voltages and it was dropping to 9.5V when the battery terminal was at 11 V.  I then did volts at every connection  and while there was no obvious culprit there were a lot of small drops.  The problem was that the heaters switch between drawing 2 amps and about 10 amps and the voltage only has to drop for milliseconds for a lock out.
I doubled the size of every cable and soldered every connection.  I gained 2 volts and its never locked out since.  I think the biggest gains came from removing  any screwed terminals and the fuse.

[Vince Newman]

I've got a made in coventry starter on my R3 with boyer ignition using a yeasu ytx14 12.6Ah 200cca battery no problem starting,
I've rerouted ALL earth's to the engine, so the only earth comes from engine/starter to the battery, this means boyer get max voltage, also i have state of the art regulator rectifier for max battery charging stand alone 40amp relay worked from tha ignition key,
This battery is the biggest that I could fit it the battery tray

[iansoady]

Interesting Vince. Have you ever measured the voltage at the BB box when cranking? Mine was between 10.1 and 10.4 which I don't believe is enough....

[limeyrob]

+ 1 to earths to the engine.  The paint on the frame and the ally case to steel frame can cause high resistance.

[iansoady]

Yes, I always run a dedicated earth to a convenient engine stud. I also add an earth cable to the headlamp / handlebars.

[iansoady]

I'm not familiar with the BBunit as fitted to the triples. On parallel twins like A10s, Norton Electras etc there is a spark every engine revolution hence a wasted spart in the cylinder not at compression. How is the triple arranged?

[Lancashire steve]

Hello All
I owned a T160 in my youth for 19 years & took interest in all technical articles written about these machines/engines.
The few British bikes that had electric starters all seem to
be compromised due to component efficiency with available battery output.
I don't claim authorship of the following as I came across it in an article decades ago.
Sadly I cannot remember where but in essence the idea was to take a cable from the starter post that becomes live when the start button is pressed to the coils.
Therefore the coils will access the same voltage as the start system when it is cranking.
It is essential to include a diode in the cable so the current can only flow towards the coils & not back to the starter.
The same result could be obtained by using a relay activated from the start button to feed the coils direct from the battery but we then add another component to the system that's not really needed.
With a decent battery & charging system this eliminates the need for auxiliary battery's & other components that appear to offer a solution but add more weight to an already heavy bike.
In my macho youth I removed the starter system as my right leg was sufficient & it shed a good deal of weight so I never tried this idea but 40 years later I'd be giving this a go if I still had the bike.
Hope this helps
Regards to all
Steve

[iansoady]

H.... in essence the idea was to take a cable from the starter post that becomes live when the start button is pressed to the coils.
Therefore the coils will access the same voltage as the start system when it is cranking.

You're still going to get a low voltage as the starter motor is sucking all the power from the battery. When I measured the voltage at the battery on my Electra it dropped to less than 10.4 volts (varying slightly as the motor turned) which in my view just wasn't enough to operate the BB system effectively.

I accept my auxiliary battery solution adds (slight) weight and some added complexity but I can live with that if it gives me reliable electric starting. Which is why I bought the bike in the first place.

[Lancashire steve]

Hello All
First of all I would say that Ian's auxiliary battery solution is a well thought out & practical solution.
The main culprit seems to be starter efficiency & aftermarket starters (madigan) for example seem to have proven this.
If a big enough modern battery could be squeezed in then possibly the simpler idea mentioned in my previous contribution may be effective.
Of course it could be expanded/modified to take a supply back to the BB unit as well as the coils.
I just thought it was an idea not to be lost for those more electrically savvy than myself to possibly consider/make use of.
Regards everyone
Steve

[DMadigan]

Some electronic ignitions do not work at low voltages,particularly the Boyer analog system. The T160 has a dual contact relay that bypasses the coil ballast resistor when the starter is engaged. It uses 6 volt coils, not 12 volt.
On a Boyer analog ignition a voltage booster is needed to keep the voltage above the lower limit. One type is an oscillator charge pump, a lm555 timer putting pulses into a charge capacitor which is supplying power to  the Boyer box. I do not know of any off the shelf charge pumps available.
There are DC/DC converters such as this one:
https://recom-power.com/pdf/Econoline/R1M.pdf
That have a 4.5V-18V input and provides 12V output at 90ma which would supply enough power for a Boyer analog.

[iansoady]

I tried a cheap version of that dc/dc converter but found it wasn't properly regulated and its output was merely a variable related to the input voltage. And 90 mA is far too low - a Boyer will pull up to 4 or 5 amps at peak.

[DMadigan]

No, the DC/DC converter is only supplying power to the timing circuit, not the coils. I have not tried that one but people have used the LM555 timer charge pump with success.

[iansoady]

I'm not sure how you can do that with the Boyer as there's only one live feed which supplies (indirectly) the coils. Although I don't know how the triple version works as I only have experience of the twins.

[DMadigan]

Maybe talking different Boyers. The analog Boyer has a power wire for the timing circuit. The coils are provided power directly from the ignition switch. The Boyer replaces the points providing the ground path for the coils.