Cams and power.

[ollieboy]

I was thinking more about price

[strx7]

where abouts are you? I think you'd be suprised freight costs

[RS13]

Just get a Rotax engine. They're designed for high altitude and low density air.

Seconded. Trust me, this may end up being the easiest option. Adapting any automotive gear to aviation involves a lengthly and costly certification process, I'm not 100% sure about regulations for microlights but I'd imagine them to be similar for light aircraft.

Rotax engines are reliable, small and lightweight, however everything in aviation costs considerably more due to the safety factor inbuilt into parts.. and you won't have to mess around with reduction gearing or anything to get the rpm you want.

A VW H engine is where you want to head. They have been used in aircraft applications for years and have aviation kits available for them.

Yup, I would look into these as well, I've seen these around for years, we rebuild them at course (I'm a trainee aircraft engineer).

[RedMist]

I'd be tempted to go TRS Microturbo... but you probably want to keep it away from anything flamable!

[ChaosAD]

ransack a hyabusa SP? for its engine

[fangsport]

Ollie, this better not be your handy work???

http://nz.news.yahoo.com/071025/3/264z.html

[ollieboy]

Haha Nah, mines still just some pieces of metal spot welded on a shed floor.

I have found, building a microlight is exactly the same as building the model glider's I used to build only on a much larger scale. It's not really surprising they crash a lot. Theres not much regulations on single seaters and they are very lightweight and flimsy.