I've also washed the GPX off of all the grease leaked from the petrol engine. That includes crud accumulated by the chain over the years which I won't be unfortunately getting rid of. That's because I've decided on the ME1003 motor along with Alltrax AXE7245 controller from evdrives.com. The MHM602 from Enertrac was tempting, but just too expensive as a whole.
I will initially use 18 pcs of small 12 V AGM batteries with are used in UPSes. The should give me a 72 V pack of about 15 Ah or 1 kWh at a weight of 45 kg. Also looking into A123 cells from the EVTV store.
Update! I have now ordered the motor and controller mentioned above. Happy happy joy joy!