www.out2win.com. They sell used and new briggs flathead racing engines as well as kt100's a briggs animal motors so on and so on. They also any stock or aftermarket parts and very good customer service complete with lots of free advice. I've gone down this road myself. Built my first briggs racing motor, locked it up during break in, tore it down for a rebuild, filed the rings a bit more and honed the cylinder for a bit more cylinder wall to piston clearance, and now she's running 60+ mph on a fun kart with a really crappy gear ratio. If I could do it all over again, I would buy the **** motor already complete though. I have done alot more machine work and porting than wka allows though so that is the only reason I opted to build my own rather than buying one built and tearing into it to get what I wanted. Here's the specs: Medium Comp Mr. Velocity cam, SINGLE COIL higher tention valve springs, polished valves, briggs raptor .020 piston and rings .065 ring gap, briggs raptor billet rod, .020 milled head with .043 copper head gasket, 3 degree advanced flywheel keyway, 3.5 horse flywheel w/ coil adapter, raptor carb, ported exhaust and intake ports, removed and polished block eyebrow, 3 stage 14" header, denso spark plug. Bought the carb, block, head, flywheel, header and gas tank used on ebay, bought everything else from the cam to the rod bolts from out2win.com. Total spent: $508 including block and head machining
