Re: reliability is a must!
On some kits there are problems with main crankshaft bearings that are substandard (missing bearings). I've had mine fail prematurely, causing a huge crankcase vacuum leak. Moisture getting inside the magneto cover causes magneto (coil) failure. If it's worth it for you to disassemble the entire engine to look at these bearings, you might have a 50/50 chance at best to discover if your bearings may be bad straight from the factory. Trust me, you will know when the bearing fails as the metal shielding disintegrates and sounds like the entire engine is coming apart. If you find metal shavings inside the magneto cover, that is what it is caused from. Other things not mentioned are sealing intake leaks with either an O-ring or RTV sealant between the carb and intake. Use one wrap of teflon tape around the throttle cup retaining nut and even RTV around where the throttle cable end inserts into the adjustment barrel. All the crankcase and cover hardware should be removed and treated with sealer or loc-tite to prevent loosening due to vibration.