There's not much to tune up on a 5 horse. change the plug. If it's still running bad, remove the coil and use sandpaper to clean the flywheel contacts. If it's a very old model, they had points under the flywheel. Not many of those left. there's an adjustment on the card. That can be tricky. make sure the air filter is clean and the fuel is flowing freely. You can also drain the carb with a screw on the bottom and get any water out. that's about all you can do.
10-28-08 - You could deck the head for a little more oomph, but the engine WILL eventually grenade itself. A carb from a larger engine (significantly larger!) would get more air in, but it would be extremely finicky to get it to run smooth. I did this on an old 8 horse, using a manifold adapter home made out of wood. It eventually burned up, but it was sure fun!
0.030" for a champion or 0.020" for NGK and others.
the best would be to use 10w-30 synthetic oil all year long
around 200 cc's on a briggs&straton. or tecumse 5hp utility motor aka "the good ol gocart motor" but specific size and displacment is often casted into the cylinder wall on the side of the motor in qwestion, on bouth forigen and domestic engins :)
There is no such thing as a Briggs and Stratton Go Kart motor. Yes, you may be using it in a kart, but it wasn't designed for it. So we need Model number to give you a proper answer, though I will give you a clue you can follow. In all the B and S engines I ever worked on, there was a small dipstick that screwed into the oil pan from the top. Most of the ones I remember took about 3 pints of oil and this could be accurately measured by this dipstick.
.030
2000 mph
1ml
SAE 30
30wt oil of any brand will work
The easiest way is to use a standard business card between the coil and the magnet part of the flywheel.
Because a 5hp motor does not have enough power to turn a 10hp load.
Run the car good