Born on the track, the 105 SX delivers the best in terms of power and performance while still remaining extremely easy to handle. Its first best quality is determined by a good power to weight ratio and its second relies on a competitive chassis.
It was presented as the ideal solution for riders who are a bit tall for the usual 85cc dirt bikes and yet too light for a 125cc machine and four years later it still goes strong, completing the customer’s needs with great efficiency. It is all due to a great start idea and the refinements brought to it as the time passed by. There is no better way to characterize the KTM 105 SX than with the words performance, power, reliability, and effectiveness.
In 2004 when the 105 SX was first introduced, the bike would have featured the 104.9cc liquid-cooled two-stroke engine already mated to a six-speed transmission and hydraulic clutch so the success would be immediate, and it truly was. The engine was fed through a Keihin PWK 28 carburetor (also to be found on the bike today) and the burned gasses were evacuated by using the exhaust valve control so, as you can see, the Austrian manufacturer made sure to equip the new dirt bike with all the needed goodies for those very craved first places on the podium.
The top notch parts were finely tuned and ended up delivering an extremely wide powerband offering great torque down low and an impressive top-end performance. It vanished its 85cc competitors and positioned itself in a class of its own, waiting for enthusiastic riders to see their way on it.
A great product right from the start, the KTM 105 SX didn’t needed many improvements or other than the ones brought by 2008 model year: revamped chassis and better power to weight ratio.
Also built for the track and clearly against the KTM 105 SX is the 2008 Kawasaki KX100. Also providing continuity and smoothness in the pass from 85cc to 125, the new KX becomes perfect for riders developing their skills and looking towards a successful riding career for the years to come.
The Kawasaki bases its racy attitude on the 99cc liquid-cooled, two-stroke engine also fueled with the help of a 28mm carburetor, but what makes the feel in the throttle special is Kawasaki’s Integrated Power Valve System (KIPS) which radically broads the powerband and determines the engine to deliver comparable low-end torque and top-end power with the ones delivered by the subject of this review. We should also take in consideration the sixth gear which doesn’t let the Kawasaki be less appreciated than its contender, the KTM 105 SX.
Even though much alike and offering comparable blasts of power, each specific model is individualized by its own behavior on the track or off the road, leaving the teenagers more and more anxious to race their bikes and improve their riding techniques.
But a real blast should also look true to its abilities and the KTM 105 SX does it successfully as it features racing looks found on KTM motocross machines. Any color is suitable for KTMs as long as it is Orange and the SX models make no exception.
The 105 features orange mudguards, orange fenders and, of course, orange front number plate, while the side panels are a combination of black, orange and the white “KTM” writing on each side, everything blending in perfectly with the gas tank.
Seat is narrow, exactly what you would expect to find on your usual motocross ride and it all finished with an aggressive rear fender, side number plates and small two-stroke specific exhaust muffler.
The track is where it belongs so that is where I took it in order to get a feel of the bike that determines so many riders to brag about it. It starts with one kick and afterwards, the two-stroke engine sound lets you know that the throttle isn’t there just to cover the space.
The ergonomics are roomy and although it is the tallest bike in its class, I certainly didn’t had problems full-flatting the ground. I quickly got used to it and after spinning the rear wheel in the dirt a bit in order to feel where it loses grip and becomes tricky I started being all over the place.
The clutch feels smooth and easy to get used too while the gearbox is very precise and no trouble at all concerning the way it operates. The SX has a gear for every riding situation or type that the rider requires, so I had a good time preparing for those long jumps on the track. I usually found myself in second or third gear exiting a tight curve and then widely opening the throttle so that the 103.96cc two-stroke torque would kick in and result in impressive and stylish jumps.
Even though I am a bit heavy for this piece of machinery (162 lbs), the engine didn’t gave any signs of weakness and the bike is a lot of fun as you don’t always have to take it easy on the throttle while cornering. You also get to pop up wheelies easily as it weights only 130 lbs, but you should only imagine how the average, a bit experienced teenager will get along with it. I did just fine, but this thought didn’t quite flow away from my head.
The WP suspensions are built to absorb the energy of all those landings, but it only made me think seriously about getting on a diet or on a bigger bike as they proved a bit inefficient with me on. On the first 105 SX models, riders complained about the seat being a bit to firm, but I didn’t noticed that even though I rode the bike for a full weekend.
I was probably too amazed by the way it handles around the track and manages to find the best trace for those tight corners that require your motocross boots to touch the dirt along with the front wheel. It is a truly easy to maneuver motorcycle in every situation. I even took it on the trails and had a lot of fun in its saddle as it performs excellent. It is where the engine proved again that the impressive torque from down low does the trick in the case of these two-strokes while the top-end is
The disc brakes (220mm front, 200mm rear) are efficient both on the track and off the road, with the front being everyone’s choice. Nothing too amazing, don’t expect to be thrown off the seat, but the brakes do get the job done.
Creating the 2008 105 SX, KTM engineers visualized a bike that would be light and robust and could easily become the definition of performance in the class in which it competes.
But the marketing department had its own idea about this bike. They planed on keeping the MSRP fairly low and they ended up selling the KTM 105 SX for $4,598.
Having the best power to weight ratio in its class and proving best for the long run, the KTM 105 SX was already an example for the competition, but now that it received its precious revamp, things are definitely going to remain the same.
KTM models are used to lead on the track and on the trails and the SX is a good example of brute force that shreds the dirt away and sees its own way towards the finish line.
Engine and Transmission
Engine type: Single cylinder, 2-stroke
Displacement: 103.96 cc
Bore x stroke: 52 x 48.95 mm (2.05 x 1.93")
Transmission: 6 gears
Carburetor: Keihin PWK 28
Lubrication: Mixture oil lubrication 1:40
Transmission lubrication: 15W50
Primary drive: 19:66
Final drive: 14:49
Cooling: Liquid cooled
Clutch: Wet multi-disc clutch, operated hydraulically
Ignition: Moric digital 2M1
Chassis and Dimensions
Frame: Central double-cradle-type 25CrMo4
Handlebar: Renthal Aluminium Ø 28/22 mm (1.10/0.87")
Front suspension: WP USD Ø 43 mm (1.69")
Rear suspension: WP monoshock PDS
Suspension travel front / rear: 275 / 288 mm (10.83 / 11.34")
Brakes, front / rear: Disc brakes 220 / 200 mm (8.66 / 7.87")
Rims, front / rear: 1.60 x 21"; 2.15 x 19"
Tires, front / rear: 80/100-21"; 100/90-19"
Chain: 5/8 x 1/4"
Main silencer: Aluminium
Steering head angle: 66°
Wheel base: 1278±10 mm (50.31±0.39")
Ground clearance (unloaded): 430 mm (16.93")
Seat height: 900 mm (35.43")
Fuel capacity: approx. 5 liters (1.32 gal)
Weight (no fuel): approx. 68 kg (129.94 lbs)