For the money I would go with the 400ex Its a great trail quad

 

great in trails, but slow

 

i have an 03 and its the best trial quad out there i think.

 

Are they good for riding big rocky hills and some mud I'm 157lbs.

 

If you plan on going through mud look at something thats not chain driven and possibly 4x4 and a 4x4 will also help on climbing big hills as well.If you want something thats the best of both worlds look at a sport utility like the scramblers, renegades, or wolverines. But at 157lbs a 300ex would be fine for you but you may get bored of it soon and wanna upgrade
so if you still wanna a sport then i say go with a 400ex if its not too much for you if your a beginner

 

If you have a 300ex, you should be on a trail every time you ride it. There is nothing better than a 1993 300ex. Go tear it up. If you get the opportunity to buy a 300ex, go for it, you won't regret it

 

I have been riding a 2000 300ex for about 4 years now the only mods are fmf exhaust,rejetted carb and air filter.it has never let me down once i can putt putt around in tight trails and it has enough power that i dont have to hunt for gears just gas it and it pulls hard.i have owned a lot of quads over the years but for the tight trails i dont have any problems pulling away from my friends on their bigger quads.the only thing i dont like about it is you have to be a damn contortionist to put it in reverse.

 

I need help my chain tensioner spins but doesn't tighten the chain? Any ideas would really help