YS.

Very cool engines. You'll have to look for one though as they only produce 4c engines now. You'd want a 61 FS for a Curare. Another nice choice would be an OS 61 SF-PABC. A little louder than the FX but a nicer engine overall. About $50 more than an FX on auction. OSSF-P and YS FS would be around the same price ~$200.

Oh, you wanted something cheaper. The Webra's should be a little less. Of course you could also buy a Chinese engine (Tower or GMS) but Ihave no experience with those so it's hard to recommend them.

David.