I am looking into building a custom quad with a twin or 4 cylinder 4-stroke motor from a streetbike. However, a heavyweight quad is out of the question, so I need to know the weight of various twin & 4 cylinder motors from around 500cc to 1100cc. I guess it would be a tradeoff between power and weight. I'm looking for around 70 minimum rear wheel HP, but not with too much weight, so I can give banshee's a run for their money in sand drags, but still have a lightweight quad that handles good.

Also, do any of the aftermarket chassis companies such as leager, roll design, etc. have engine mounts for any streetbike motors?

 

I think that you will have to make your own engine mounts. I would go with a after market chassis from like lone Star,one of there drag chassis so it might have more room to stick a bigger engine in it and able to support it's extra weight.I might just be talking out my *** but im only 14. So don't laugh. But when you start a big project like that it's goin to cost'ya. Ever seen that guy with that Quadzilla with the Suzuki 1100GSX or what ever its called. Im sure you have seen it cause its been in dirt wheels before and Houvos Grandes, how ever you spell that. Well that would be an awesome quad to have built. I'm sure it cost around $20,000 for it. Why don't you just buy a Banshee and buy One of those Turbos for it from Alba when it comes out....And improve on the chassis and but all aftermarket parts for it?????.......Well later,Kenny.....(I bet you could find millions of bad things wrong with a banshee )

 

I don't think you are going to get a good handling quad with any 4-stroke street bike motor. 70HP is easily attainable through mods to a Banshee motor. David Allen Racing is selling a 670cc drag Banshee. It uses a Rotax 670 top end on a modified bottom end. The cylinders are mounted backwards. It uses crankcase induction on the front of the motor. The exhaust exits to the rear and heads straight back. There is plenty of room for the pipes because of the long swingarm.

 

I have converted several quads to 4 cylinder Twin cam multi valve engines and can say that you need to get your hands on a Yamaha EXUP motor. The 400,600 and 1000cc motors are very compact and lite and put on the bench side by side there is suprisingly little difference in physical size between the 400 and 1000cc motors. Dont forget to get the down pipes with your engine as they are fitted with a small power valve, and this will help with obtaining max HP.. I agree with the other guy that you can get 70+ horse from a banshee with mods but how reliable it is compared to a stock 4 cylinder motor is a nother story.. If you want some more help then e-Mail me back.
You will also need to cut a hole in the top of your crash helmet before riding one of these conversions so that you can take your brain out each time you ride your quad.. Beleave me it helps.....