Inexpensive engines?

[stoogippeme]

Hello everyone this is my first post but I have been lurking and learning alot from everyone here, the reason I finally decided to signup and get an account is
so that I can find out if anyone anyone tell me where I can find some inexpensive engines I am about to do my first bike build and need some guidance in where
to find parts.

[Bikerpunk]

Depends on the kind of bike, doesn't it?
You can get a surplus XS650 from a lot of salvage yards for about $100, mostly complete. Grind off the Yamaha logo, jig up the frame and extend it, and you have a damn nice looking bike that's VERY close looking to a 70s era Triumph bobber for little coin.

[Head Wreck]

and a little more reliability i dare say