Bone stock, with RTR components, you can expect 32-40mph from the Hyper 7 buggies.

You can of course find a smaller spur gear and a larger clutch bell to go faster, but that may well overtax the engine.

The other option is to buy a kit, and get a big block .26 or .28, even a .30 engine, if all you want is speed.

Buggies are heavy. Very heavy. It takes alot of power to get them going, and even more to keep them there. 50mph is about max for a single speed transmission 1/8 scale. I've seen it done with a .30 engine and 35% nitro. But the engine lasted only 4 tanks before blowing the connecting rod.