Re: Racing Go-Kart Project
The acceleration at 2 secs is a bit optimistic but you are looking at a shifter kart. If it's not a racing kart frame, built by pros don't bother. You'll fold up a yard kart with an engine that big. Don't use a cage or belts in a vehicle that small. If something happens you want to be thrown clear and not taking the brunt of a 200# plus machine strapped to you. The kart will weigh around 200# or so. The pros race at 365#, semi pro/am at 385# and the masters, or old fat guy class races at 400-415#. All including the driver and all the safety gear.
Shifters started using motocross engines, two strokes. Don't bother with a 4/, they don't have the right power band, are heavy and don't fit well on a racing kart. Honda has a program for kart racers but over the years the sanctions have gone back to a stock CR125 to reduce costs. A ready to race stock CR125 fitted to a kart with carb to exhaust is about 4 grand new. They keep the resale value well. The mod moto engines after significant mods are quite a bit more expensive. My first in 2001 cost about $6500 to build and about $3500 a year to maintain. The stock CR125 costs a couple hundred a year to maintain. Since then they have built kart designed 125cc shifter engines but they are still up there in price and cost to run, about 4500-5000 new and a grand a year or so to run. They're called KZ right now but in the past were called ICC. Reine Piersen at Swedetech Racing Engines in Elk Grove CA are the ass slappin' daddies of small, high hp 2/ racing engines in the US. They do GP bikes as well.
To get close to that kind of performance it will cost at least around 10 grand for something safe once all is said and done. Might be able to do it for a bit cheap but if you aren't familiar with racing karts I doubt it. You'll need a 32mm shifter chassis with front brakes. You'll cook rears alone and won't be able to stop.
Price/performance wise you get more bang for the buck by building a low end bracket drag car. I'll look at some old data tonight from when I was running the shifter nationally. The shifter was faster than the Miata I'm building now and the stock car I raced the last couple of seasons. The top speed for me was around 107 mph but I was always 70-100# heavy for the class. I'm too damn big to kart. With the little racer size guys you can hit 115 mph or so.
Opps, stock CR125 about 34 rear wheel horsepower, mod CR 125 45ish rwhp and purpose built kart engine, 125cc 2/ 48ish rwhp.
Forgot I had some data with me now, 2008 SKUSA Supernationals running Spec Honda S4 (stock engine, old guy, 405# class) with a scale weight of about 470# I was doing 0-75 in about 7.5 secs. We weren't geared for acceleration, we were geared for a 1200' straight. The pros with the mod engines were doing that same leg in under 4 sec.
