I haven't ridden either yet (I will get a -02 520 SX in less than three weeks, can't wait), but the bikes are the same size and virtually the same weight (within a few pounds or so), so the difference will be the motor.
From what I've heard, the 400 is a bit less tiresome and due to the power delivery, a bit easier to ride. If you're not huge(I'm 92 kg), the 400 will pull you around VERY fast(I've seen people win races on it), and at anything less than pro level, the engine will not be a hindrance.
It depends on what you plan on doing with it. For just motocross I would consider riding a 520 but I also do alot of off-road racing and the 520 is just to much for me to handle in the woods. I'm not a very big guy (5'-9", 170lbs) and it was just to much for me to handle.
I have a '01 400 SX that works great. It will out run 250 2-strokes on the starts and on straights but has a very seamless powerband that will never wear you out.
Hey Knobbiethrower, I regularly beat guys on 520's (even on straightaways)
because they think that because their bikes pull easy wheelies and have massive power that they will be able to win races or beat me to the next turn. NOT TRUE!!! My 400
is much easier to ride and race and find traction too. The only guys that can
really put the 520 to REAL use are top experts and pros. Fact is, it is the rider, not the bike. Just remember, John Dowd still gets beat regularly by guys on 250's too. J.D., For tighter tracks and woods, the 400 really is superior. For hill climbs, open desert, or roosting your buddies, or just to brag that you have the bike with the most power(which I highly doubt that you will ever have the thing WIDE OPEN and in total control except in a straightline drag race) then the 520 is for you. Insane, ... seriously consider your riding ability, and be honest with yourself. Then consider what type of riding you will be doing. Then make an educated choice. Erik
KTM400Man, All those comments about riding ability are true and I agree 100%.It is more demanding to RACE a 520 vs 400, however it is more fun to ride the 520 in my opinion.One thing puzzles me, I believe late last year and early this year you were looking to sell/trade your 400 for a 520?:p
Knobbie, I was going to go that route, but decided to stick with the 400. I got the chance to ride my friends 520sx a couple of times this year at different mx races (due to flat tires during two different motos) and even though the power would be advantageous on certain sections at higher speed tracks such as Mammoth's big uphill, or the long start at G.H., I prefer the smooth power delivery of the 400sx for racing most. It is far less tiresome to race. If I felt like I couldn't win any more races because my bike was underpowered then I would get the 520. As of yet, that's not the case. I would like to have a 520 as a spare bike for playriding (and I will agree with you that the 520 is a BLAST to playride on) and the ocasional high speed track, but until I can afford one as a spare, I'll stick with what I have. I have actually been thinking about getting a 125sx or yz125 for a spare/play bike. Erik
I like POWER and the 520 feels smooth compared to the Blue thumper I had before! If you are going to ride desert as well as MX on an "SX" you may want to stick with the 400 to get the 6 speed gear box. You can convert a 520SX to 6 speed ( I know one guy in Las Vegas that did...about $500) or just do what I did and buy a 520 MXC. I'd guess my 520 has a bit less hit than the SX do to the BIG MUFFLER on it...but I sure like the quiet! ;)
All things considered, the best choice for me was the 520. I ride MX,hare scrambles and turkey runs here in the northeast.I had a chance to ride both before making my decision and chose the 520 because it was simply more fun to ride and that is why I ride for Fun.If I could have another bike it would be a 400exc!;)