Good question, riding at a race pace.

[yellow400ex05]

Well i really want to ride doen my trails with a couple of friends at a racing type pace revved out in 4th down straights and whoops just riding fast half throttle maybe a little more, not like rev limiter stuff just riding fast ripping around winding out the gears and on the gas. Would it be really hard on the engine and wear it down badly, or would it just mainly waste gas?

[JOEX]

Originally posted by yellow400ex05
Well i really want to ride doen my trails with a couple of friends at a racing type pace revved out in 4th down straights and whoops just riding fast half throttle maybe a little more, not like rev limiter stuff just riding fast ripping around winding out the gears and on the gas. Would it be really hard on the engine and wear it down badly, or would it just mainly waste gas?
It's not wasting gas if you're having fun!:D

As long as you're maintaining the quad properly don't worry about wearing things out prematurely. Clean the air filter regulary. Change the oil and oil filter regularly. Inspect the chassis for loose bolts and the electrical system for loose connections. The chain and sprockets along with break pads are probably the most common wear points on a stock machine.

The 400ex is pretty durable but like any motorized vehicle it needs some attention to general maintenance.

[H_W]

Originally posted by yellow400ex05
Well i really want to ride doen my trails with a couple of friends at a racing type pace revved out in 4th down straights and whoops just riding fast half throttle maybe a little more, not like rev limiter stuff just riding fast ripping around winding out the gears and on the gas. Would it be really hard on the engine and wear it down badly, or would it just mainly waste gas?

That would be typical riding on a sport quad. That is what it is made for. Like Joex said, just do routine maintenance and you will be fine. The 400ex is really reliable.