We race the clone engines on our karts at 6,000 rpms, with only a 600 rpm drop through the turns on a dirt oval... with a 30 dollar cam, a muffled AKRA race exhaust header, a set of 10.8 pound springs and a k&n style filter we can equal the power that a $1500 race prepared flathead engine makes all for around 350 bucks if you are skilled. In 4 years now of running this platform, the only problem I have had related to the engine was I wore a top ring out in one of them having 18 months of racing, and that top ring was a softer ring, not a stock chromed ring. Of course, I would recommend starting out with a clone engine that was purchased from a race shop, usually they can be had for around 100-120 bucks. Doing this will give you better tolernaces that say the hit or miss on the harbor frieght stuff.. sometimes the HF engines will have the piston .030 in the hole, whereas a engine from a kart shop made by ducar or dupor should be closer too .005 in the hole. These engines do not include an exhaust or air filter, or a fuel tank, but if you are planning on some upgrades, you are going to throw those stock pieces away anyway...
Many places, like ARC Racing, sell a U-Build-It Kit for around 250 dollars, maybe less, haven't checked in a while. This will give you a solid engine with AKRA rule race tolerances, and probably make atleast 2 to 2.5 HP right off the bat if not more..., all for around $250 bucks if you can swing it... Also note, the engines from Harbor Freight are not 212cc, and some of the internal and external measures have been changed between the HF 212 Predator and many of the 196cc clones. For example, many readily available clone cams will not fit in the predator.