S4 generator

[BrianReynolds]

Hello All,
I am in the process of assembling my ‘57 Mk2 S4 engine, about to assemble and install the generator so I can install the cam chain and set the valve timing. I would like to convert to 12v, there appears to be conflicting information relating to using the original generator for 12v, some say it can be used as is, others say to replace the coils etc. The alternative is to purchase and install the alternator conversion. I thought I would ask the experts, anyone have experience with this? Alternatively I can leave it at 6V but I would prefer to use an electronic voltage regulator if available. I still have nightmares relating to the old mechanical regulators. Also, I have a new “Ultra Spark” electronic ignition kit that came with the bike, I have not been able to find any reference to this, presumably obsolete?

[simon.holyfield]

I think a lot of us are using DVR2 or V-Reg2 regulators with the standard C35SD generator. The secret is to have a big enough battery - mine currently has 19 Ah of battery capacity; I ran it with 12 Ah for a while and had many more problems with misfires or poor starting. They don't like towns!

[Roger Gwynn]

Most electronic regs cannot cope with the massive output of the C35SD, the A-O one can, more info in general here https://draganfly.co.uk/product-categor ... ng-system/
Basically you can convert to 12 volt but the results will not be very satisfactory unless you change the armature and field coils to 12 volt ones that would have different windings, if they existed, which they don't. Unless you intend to do a lot of night time riding there is little point in changing. Modern LED bulbs are great even on 6 volts it just requires all the connections to be in good condition.

[Chris Sealy]

The best solution, in my opinion, is to remove the lead plates from the battery and replace them with LiFePO4; Lithium cells. You get a lighter, longer lived, higher capacity, faster charging, and maintenance free battery.
The only problem is that no one makes a LiFePo4 to fit the square four; so you have to make your own or get someone who knows what they are doing to make one for you.

[Roger Gwynn]

I use 4 of these with the back cut out of the battery box. https://draganfly.co.uk/shop/81928/luca ... x70/#BAT2A they will give an 18 amp hour at 6 volts or 9 amp hour @ 12 volts