KTM HAS only tweaked both the two-stroke 250SX and four-stroke 450SX for 2006, for both bikes were competative and fun and sometimes it simply isn’t worth messing with a good formula – and some of the tweaks have made the bikes much better to ride, too.

Both look great with their radical new styling and graphics. If you are a pro racer you might feel you have to be on a 450 to be competitive, but if you are a social racer or don’t race at all you might find the simplicity and rush of the 250SX to be the better option overall.

With serious bottom and mid range as well as an awesome top end, KTM’s 250SX is sure to excite. You can roll the power on early in a corner and then bring the power on hard on the exit and the SX seems to warp you down the track. It is surprisingly predictable, easy to control and a hell of a lot of fun. For ’06 KTM designers updated the powervalve with a new flap, main spring and modified cylinder, which has helped beef up the bottom end and smooth out the rest of the power delivery. The piston is lighter, the carby has shrunk from a 38mm to 36mm and the CDI has been updated to get the best results. The gearbox has also had some tweaks, with a taller second gear that gives a smaller gap between second and third for better acceleration. The motor is crisp and clean and gives the rider some serious options depending on ability or track conditions. The 250 also gets a new Brembo clutch master cylinder, which is similar to what the factory teams have used in the past.

KTM’s trusty single cam 450 has made many friends over the years. It might not have the arm dislocating hit that some 450s used to have, but it has always been a bike which is easy to control. Power is strong down low and builds nice and steady for maximum traction. The top end is strong but not overpowering and there is plenty of over rev for the times you need to hold a gear. The motor started well most of the time but when it didn’t it was a hassle having to access the hot start from the side of the carby. It is surprising that KTM haven’t got it on the handlebar where it should be. The motor is very smooth and easy to dial on, and isn’t likely to stall just because the revs get a little low.

The four speed box is nice – it takes some of those extra shifts out and makes the ride a little less hectic when you are getting tired. The motor seems to suit the four speed tranny well, and the Magura hydraulic clutch unit gives a nice light and consistent feel.

For 2006 the motor hasn’t had many updates. Possibly because it was pretty good before hand and also possibly due to the fact that rumours are pointing to an all-new motor for 2007. The crank shaft has been updated, it is now stiffer for improved durability. Getting fuel to the combustion chamber is taken care of by a 41mm FCR carby which has new settings for improved performance.

The alloy skinned muffler looks the biz and keeps the noise down to a sensible level. Together with the stainless header it seems well matched to the motor and there doesn’t seem the need to spend mega bucks bolting on an aftermarket system unless you are searching for every bit of power or gram of weight saved.

The new KTMs look tough. Partly because of the new black highlighting (rims, frame, forks etc), and partly because of the chassis design. They are light, narrow and very adjustable in the handlebar area, which is great for a personalised set up. The new frame has a slightly steeper head angle for good steering, and steer she does. Picking lines, ruts and general control is excellent. As has been said in the past, the front can get twitchy on rough, choppy surfaces at speed, but with nice smooth power pushing the back wheel it seems to alleviate the problem. Lighter riders might find the suspension a bit on the firm side in these conditions but we tweaked the compression damping slightly and found we were able to find a good balance of front wheel stability and big impact absorption.

Apart from the new colouring (black forks, orange PDS shock spring) the suspension has some new settings and new coatings to reduce friction. The shock also benefits from a new bump rubber to improve control when bottoming out. A new cast alloy swingarm is stiffer and stronger.

The Brembo brakes are great with plenty power and feel. Some people find the rear a bit touchy, and a nice light touch will give best results. Maybe different pads could give them a slightly less responsive feel.

The 250 weighs in at just under 98kg (ready to ride, but with an empty tank), while the 450 has an extra 7kg to push around at a shade over 105kg. At times the extra weight is noticeable, but other times the 450 seems easier to deal with, because of the power characteristics of the four-stroke.

Both bikes have a fresh new look, just like they have been prepped for racing. And both bikes are solid, the only question mark would be the nervousness at high speed and the forks for lighter riders. We got more of a buzz from the 250SX – it is fast, tough and fun - but it is also very satisfying to ride. Most people have their minds set on four-strokes, but others are looking at getting back onto a two-stroke after spending some time on fours.

We did find the front end was better on the 250, it seemed easier to tighten up in turns under power and skip through the rough sections much better. But if the conditions were more slick the 450 would probably shine. Either way they are both nicely finished machines that are basically ready to roll on the track.