Need a smal, 4-stroke, water cooled engine...

As above - a motorbike engine would be a good starting point. No dizzy as such, but older ones just use some form of sensor (optical/etc) to trigger an amplifier, and fire a wasted-spark setup.

Arguably... more reliable than points and dizzy

Nice and light, fairly easy to get hold of on ebay once you know which model suits you best. FD is (AFAIK) simply made by the output sprocket ratios - so if you fit a 1:1 sprocket ratio, it's direct drive


What's it needed for? Might give a few more options - or rule some out

Yes, constant RPM. Most smal bike engines seem to be air-cooled, though. And a scooter engine is too smal again...

I think, a smal diesel (Kubota for example) is much easyer to obtain. I've read a bit into it and a dual-fuel engine is probably going to be the best solution, but will require some experimenting, though. Methane will work well in a diesel-engine (with a squirt of diesel or SVO to ignite it), from what I've read so far. As a bonus it will be able to run on SVO or other stuff, if gas should run out...

I'm still in favour of a petrol engine, as it seems easyer and needs only a single fuel... What about outbord boat engines? Are the usually water-cooled or air cooled? There seems to be a lot of them available on ebay. But I know next to nothing about them...

My experience is limited to knowing someone who wanted to use one for a little go-cart and it was underpowered.
I think the smaller, cheaper, air-cooled ones will be underpowered.

Would there be any way you could add fans to the case or frame?[/quote]


I've read about guys putting small diesels into motorbikes and they seem to come without cooling in the original application, so they run well enough with no cooling by design and run better when they're in bikes because of the airflow.

I'm enjoying imagining what you're up to...

No need to be sarcastic, I've asked a question that was specific enough, without needing to explain any detail. I know many people try to come up with new ideas rather than awnsering a very specific question in 'the interweb'. And despite 10 years of using interweb forums I still make the misstake of not revealing the whole story of my life, instead of asking a simple question ;D

I you realy like to know; a micro-power station. And all the info I'm missing is; which engine could I use for that? A engine that's a) petrol b) smal c) cheap and d) water cooled.

Does the new info help in any way awnsering the same specific question? I think not It'll only get me suggestion like 'how to convert from air cooled to water cooled', 'build a nuclear reactor', 'why???', 'it's useless, try horse poop in an oven' etc. etc. Concentrate on the main subject! That's why I didn't write down every little detail.... You don't need to know it, to awnser my question. If you can't, I'm not interested. Sounds harsh, but it's the truth...



That's a good idea! I didn't think about these...

You might be better with something like a 500+cc supermoto engine. They'll make the power/torque you require at a much lower rpm than a smaller bike engine. Might be best trying to find dyno sheets for the engines, I assume its no good making 30hp at 9000rpm cos it'll be mega noisy.

Howabout a Reliant engine from the Robin? aren't they around 750cc ?? With the added advantage of being Aluminium as well,so light weight.?

A lot of boat engines including outboards are watercooled, silly not to be really what with an essentially infinite supply of cold water surrounding them in use. Outboards tend to take in water in-front of the prop and chuck it back out above it, no radiator or anything as obviously the hot water's just dis-guarded so doesn't need cooling. It's fairly clear which are water-cooled just from their external appearance, being fully-enclosed with no concern for air-flow around the engine.

I'd be guessing a boat engine would actually be very suited to what you're after. They're speed range and times spent at fixed speeds will probably be closer to a generator than a car engine would be, and they're less worried about getting the coolant hot because it's continually renewed, so may well heat the water better.

Edit: Also what he said ^ about a heat exchanger on the exhaust.