An attempt to weigh one of the four packs on the bathroom scales says they're 10kg on their own. Then , weighing myself first holding the pack in my arms and then subtracting my weight, the scales read just under 10kg. (bathroom scales aren't too accurate at the bottom end of the range usually, but this doesn't seem too far off....I suppose it depends if yoiu worry about half-pounds or not !)
The weight of a single cell is about 45g to 47g.
I have 210 cells, so 10000g / 210 cells = about 47.5g per cell inclusive of solder, tabbing strip and plastic spacers.
My 18650 pack weight should finish up at about 43kg, including enclosures, mounting hardware and electronics.
The dry weight of the engine which I removed is accepted to be 140-150lbs (min 65kg) , (there was also a 1000cc engined version weighing in at 180lbs !) Add to that 65kg the engine fluids (3L oil + 3L water) , the very heavy exhaust (11kg) and a tank full of fuel (21.5L at 0.737 kg/L) the total weight of the original engine and support system was about 97kg. Considering the starter battery and frame mounted electronics (ignition coils, rectifier, ignition controller) and I reckon that I have about 100kg to play with in order to stay within the limits of a standard bike
The electric motor I'll be using, (unweighed so far....or perhaps I already did that but forgot !) must be in the region of about 20kg, so that's about 40kg less than stock so far. I need to add in 24 headway cells, the motor controllerand possibly an onboard charger too....I think even then I still have plenty of headroom to install the supercapcitor and still run lighter than stock
The Headways would add another 740Wh, so 4.5kWh total, and if I replace the volume and weight of the supercapacitor with more Headway's, or even more 18650's I could potentially get to over 6kWh which I think would give me a very nice range.
Matt, for a 12V 14Ah system I guess you would need to go with 4 series cells, for 12V - 16.8V. Just plucking figures out the air here for convenience, if you used 1400mAh cells you would need 40 (4 series, 10 parallel, '4s10p'), at 47.5g/cell to get a pack at the high end of your requirements weighing just under 2 kg. with cells of 2100mAh capacity it would weigh 33% less.
All I would say for your application is that some sort of low voltage cutoff device would definitely be required for unattended operation !