I'm new to this forum, but I've read several threads discussing potential low budget aircraft builds. One of these threads that caught my attention went over the biggest problem (in my opinion) with a low budget aircraft. The engine. If you plan on buying a purpose built aircraft engine, you might as well kiss affordability goodbye. The thread I mentioned above (I'm unable to find it, I read it about a year ago and I'm also posting with a low quality smart phone) discussed alternative aircraft engines. Several people had the idea to use industrial engines, like Briggs and Stratton V twins. Another idea that came up was to use a motorcycle engine. Yet another idea was to use a Go Kart racing motor, like a Vegas Carts 460. These are all great ideas, but there were a lot of naysayers and armchair experts as always, so I don't think anyone came up to a conclusion or found a solution. I'd like to offer proof that you can successfully use something besides a purpose built $2500+ aircraft engine. I hope my thread helps the low budget cause. I am looking to design and build a low budget ultralight aircraft, and I always run into the problem of finding a suitable low budget engine. Here's a person that uses what looks to be a Honda gx390 with a belt reduction on a SkyPup ultralight. It flies. It takes off under it's own power. Sorry, but I couldn't find any specs. https://m.youtube.com/watch?v=ztJE0-NbKAo Here's a person that uses two performance modified 6.5 hp Honda clones on a Lazair ultralight. You got it right. A twin engine ultralight. https://m.youtube.com/watch?v=rehhYT-g9Mk Here's the thread where the twin Honda clone Lazair guy goes over some specifics. I'm assuming it's the same guy from the video above. Apparently each motor produces 75 lbs of static thrust at 4400 rpm. http://www.lazair.com/forum/viewtopic.php?p=8194 Here's a person that put a Honda gl500 engine on his CGS Hawk ultralight. Apparently it climbs at 8-900 fpm and cruises at 70 mph while using 1.5 gph of fuel. I highly encourage you to read the description of his video for specifics, and please watch his other videos if you doubt the airworthiness of his concept. This is my favorite idea. Honda gl500 engines are notorious for their reliability. https://m.youtube.com/watch?v=NnGXUKz1Wpg As a disclaimer, I am not an expert aeronautical engineer. I have never built an aircraft. I am a **** good mechanic, and I have a pretty good understanding of physics and engineering. I would like to build an Ultralight aircraft of my own design very soon. I've been working on the design for awhile, but haven't really gotten too far because I can't decide on a motor.