KTM 125 SX/ 150 SX
By TMX Archives on 2nd Jul 08
The off-road press have run out of superlatives to describe the 125 SX and its recent new sibling the 150 SX over years and one lap on either bike tells you exactly why this is the case - they are both hands down among the very best motocross machines on the market whatever stroke or capacity.
The 125 SX has been at the top of the two-stroke tiddler tree since before the turn of the millennium and despite the best efforts of the powers that be and the Japanese to marginalise 125's KTM has continued to forge ahead with two-stroke development year after year, reaping the rewards in strong sales and rave reviews about a pair of bikes that epitomise just what is so great about two-strokes.
2009 is no different and once again KTM has eked a bit more power, a bit more smoothness, and a bit more enjoyment out of its most beloved bikes.
Although the 125 SX and 150 SX benefit from different cylinders the performance of both is very similar in general and both recieve a significant boost in performance from the addition of yet another new cylinder and the smaller 38mm Keihin carb unit.
Increased bottom-end power without sacrificing overall power was what KTM were searching for with both of the developments and they have delivered here making both bikes noticeably stronger off the bottom-end and through the mid-range, requiring less clutch to keep on the boil and making for a smoother ride, and again a small step closer to the four-strokes.
The 150 SX in particular is impressively stronger right off the bottom and pulls quicker and stronger through the rev-range out of corners. The power delivery on both bikes though is more linear, progressive and manageable right the way through the range as a result of the increased bottom-end and it is easier to keep the bike in the meat of the power.
The performance from the mid-range upwards is as formidable as ever and when you get both bikes into some grippy soil or upright and in a straight line up through the gears the over-rev is really sensational and you can pull gears for what seems like an eternity. This is where the 150 SX especially stands out above its smaller sibling, pulling impressively longer and harder.
What really stands out on both bikes to me though is just how controlled and progressive they are despite their very strong and fiery power. The torque is impressive and they are eminently rideable, and combine this with the already superb handling and forgiving chassis that has already been talked about and you have a pair of bikes that handles better than any other in the KTM range.
The traditional steel chassis is the perfect match for a 125cc or 150cc engine and offers incredible feel and stability in corners, and the super-light 90kg weight means the bikes are a dream to attack corners and ride aggressively with, and the revised suspension front and rear both bikes provide a more supple, positive and balanced ride, particularly on the front-end which benefits from the slight softening that all the bikes seem to have, and makes holding lines and attacking rough sections a more enjoyable and rewarding experience.
The 125 SX and 150 SX are thoroughbred racers and really it is hard to find fault with either machine without getting really, really picky. Without doubt you'd be hard pushed to find a more enjoyable and fun motocross bike to ride all year.
Specification:
ENGINE
Type: Liquid-cooled single cylinder, 2-stroke
Displacement: 124.8cc/143.6cc
Bore x Stroke: 54/ 54.5mm/56/58.4mm
Carburettor: Keihin PWK-S 38 AG
Starter: Kickstart
Gearbox: Six-speed
Clutch: Wet multi-disc clutch, hydraulically operated
Lubrication: Mixture oil lubrication 1:40
Primary Drive: 23:73
Final Drive: 13:50/14:50
Ingnition: Kokusan
CHASSIS
Frame: Central double-cradle-type 25CrMo4
Subframe: Aluminium
Handlebar: Renthal, Aluminium 28/ 22mm
SUSPENSION
Front: WP-USD 48mm
Rear: WP-PDS shock absorber
Travel Front/ Rear: 300/ 335mm
BRAKES
Front/ Rear: Brembo disc 260/ 220mm
WHEELS
Front/ Rear: Excel 1.60 x 21"; 2.15 x 19"
DIMENSIONS
Steering Head Angle: 63°
Wheelbase: 1,471mm
Ground Clearance: 390mm
Seat Height: 985mm
Fuel Capacity: 8 litres
Weight (without fuel): 90.8kg
