– 2 stroke Motorcycle/dirt bike engines – are they an option? If so, what have people been using? I assume not as they don’t use liquid cooling, but karts use radiators.
Karts have primarily used 2-stroke motorcycle engines. The most popular are the 1999 CR125 w/ a 1997 CR125 6-speed gearbox. The 2001 is probably the 2nd most popular engine.
Most shifter karts use the same frame-rail spacing for the engine – get the mount that goes with your engine matched to your frame-rail diameter.
I think mounts exist for YZ engines, KZ (kawasaki), and other motorcycle-based engines.
– Are there such things as direct injected 2-stroke shifter engines?
Maybe. None that are legal in anything but some sort of “unlimited” class. Do you have $10k?
– What are the top 3 go kart specific shifter engines people use? What are the reasons for using them?
These are often referred to as KZ, KZ2, and ICC engines (used somewhat interchangeably)
TM (historically strong motor throughout global competition) K9, K9b, K9c, KZ10, KZ10b, KZ10C
– What engines have the most aftermarket support and spare parts? This is very important as I don’t want to run into an issue where I can’t easily obtain a part.
Honda CR engines.
Basically, pick your engine based on what club/group you plan to run with locally. Or, if you don’t care about placing, put whatever is cheapest, and reliable.
I am sort of in the same boat as you – I do a few races a year at most. I have a 2008 kart with an early TM K9 engine (it’s what I found first). I would like a CR engine, but the initial buy in was twice what I’ve got in my TM even after a full rebuild.