A few years ago I bought a Kawasaki Mule (a bit like this but in worse condition) from a scrap yard with the intention of getting it going again.
Main problem was that a rear drive shaft was missing and the cabin floor had rotted away and there were no brakes – it was also unkown if the 19hp petrol engine ran.

The floor is now fixed and the driveshaft replaced and the brakes shouldn't be too tricky to fix but the engine only runs on one of the two cylinders (they are rather liable to do this).

I was going to strip it down and replace some rings as the compression seems low, but now I'm thinking that maybe I could get hold of an electric motor from somewhere and use that instead of the petrol engine.
Drive would be pretty simple as the original engine drives a separate gearbox via a belt, so should be a fairly simple task to hook the two together and there's foom to fit a battery tray for a few batteries.

But I have no idea what sort of motor I should be looking out for. anybody experienced with this sort of electric motor?

You've got two choices.

1) get a motor, batteries and drive electronics from something with a similar application and use that – a milk float or a golf cart for example.

2) do a lot of research and learn all about the subject.

Option 1 is probably easier in this case and would most likely be ok. 2 would be fun though 🙂 There are loads of types of motor for every application, and they need various control strategies…

i looked at upgrading the kids toy electric quad and the robotics sites have lots of stuff on motors and gearing including some bigger stuff

The design and suitability of the motors and electronics to run it need a decent amount of time and effort to think about unless you just want a hacked together solution for the fun of it. Many of the ideal solutions will require high voltages (500v+) and controllers but a rough and ready system could be done using odds and sods or re-purposed parts. Easier to fix the petrol engine, by far, but not as much fun I suspect.

CK that's why I suggested gutting an already existing EV.

If you want an even funner challenge, how about a gas turbine powered one?

Given the kind of use that kind of machine is designed for, I suspect raiding a milkfloat for all its lead acid batteries would lead to massive ruts left all over the shop and traction problems.

Few things that are going to be problematic:
Lead acid batteries will weigh a lot more than the existing engine.
Motors tend to run at far higher RPMs than engines.
All torque is available from zero revs, so if you put the batteries in the right place you could do some fantastic wheelies.

Good points Tron. I can pretty easily carry the engine around – batteries may make it too heavy for the proposed use of big/cool/fun wheelbarrow/gokart. Road registered as well which would be fun!

Some people reckon a elec motor can cost £2000 for the conversion???

A man in Melbourne, Australia did it with his Talbot sunbeam-light as **** and with a washing machine motor and a boot full of car batteries on the Discovery channel.

He had a 30 mile range and a top speed of 55mph, mental but he was a retired engineer.