- Single cylinder, 4-stroke
- 4 gears
- Keihin MX FCR 41 Carburetor
- 449.3 cc; 477.5 cc on the 505 SX-F L
- Top Speed:
- 110 mph
Leaders of the MX1 and MX3 classes, the KTM 450 SX-F and KTM 505 SX-F feature the latest technology concerning both engine and frame which makes winning a sweet confirmation of the already expected results. The light electric starter only makes the rider’s life easier when things don’t go as expected.
Characterized by reliability, performance and ingenious features, the bikes reviewed have all the chances to win every competition they enter. Helped by 449.3cc respective 477.5cc single cylinder, four-stroke engines, these KTM models use the latest technology in order to prove successful. 2008 announces as a big year for motocross, as well as every previous years since I don’t know when, so KTM is offered even another chance to make a point. And it succeeds every time.
But are KTM motocross bikes needed to make a point? Usually not, but given to the fact that the SX-F racing motocross range was introduced in 2007 it would be nice to have see the bikes climbing the success mountain in no time.
KTM went up against the best in the MX class and many consider the Honda CRF450R as being among the best. Totally revised for 2008, the CRF450R receives all-new works-style brake rotors, retooled frame geometry and the revolutionary new Honda Progressive Steering Damper which makes for the Honda to radically stand out on the track. Making that happen is the 449cc liquid-cooled single-cylinder Unicam four-stroke engine which was mated to a close-ratio five-speed transmission, compared to KTM’s four-speed gearbox. MSRP: $7,199.
Yamaha couldn’t stay out of this battle so it went the whole way with the 2008 YZ450F, a bike that is constantly improved and bragged by its manufacturer. Why wouldn’t it be? A 449cc liquid-cooled DOHC four-stroke; five titanium valves engine won’t heart anyone and the five-speed gearbox is superior to the one found on the subjects of this review. MSRP: $7,099 (Team Yamaha Blue/White) and $7,199 (White/Red).
Everybody claims to have gotten the recipe exactly right, but Suzuki is the loudest. The all-new RM-Z450’s 449cc, four-stroke, single-cylinder, liquid cooled, DOHC, four-valves engine is now fitted with Suzuki fuel injection system, like on GSX-R supersport bikes so it is expected to show another face of motocross racing. MSRP: $7,199.
Last, cheapest, but not the weakest. Yes, we’re talking about the 2008 Kawasaki KX450F a motorcycle disposing of the smoothest and most user-friendly power delivery to yet be seen on these kinds of bikes. Its engine is a 449cc liquid cooled, four-stroke single with DOHC and four valves and the gearbox, you guessed it, a five-speed unit. MSRP: $6,999.
Could you distinguish the one from the other? You don’t stand a chance! How could you when the bikes are absolutely identical looking? KTM intends on offering diversity and that is the reason why the displacement issue appears, but apart from that you will find it impossible to make a difference from one another.
A high front fender and stylish front number plate characterize the machine first approaching to the finish line, but once you get a better look at it you will notice that good looks is a true quality of the SX-F.
Side number plates are aggressively styled and speak about the sharp attitude implemented to this motocrosser. The panels blend perfectly in with the narrow seat and with the bike’s rear end. Decals are pretty unique and appropriate for this kind of ride, as well as all that black covering the Excel wheels, the fork, the mudguards and the exhaust muffler.
So even if you are not able to distinguish the bikes between them, you will definitely notice them when riding along its competitors.
These bikes are definitely among the most impressive motocrossers I’ve ever ridden. Simply wonderful performing and incomparable to small two-stroke engines that everybody brags about in their attempt to resurrect something that certainly I consider very much alive, but that’s a whole other story. Just for the record: you will not see the KTM 450 SX-F or 505 SX-F beaten by some 250cc two-stroke motorcycle!
Having found my way on the biggest SX-F models I just couldn’t take the kid smile off my face as the bikes are wonderful on the track and invite you to jump the hell out of them and so prove that KTM has its place among the five motocross builders guaranteed. Both engines producing over 60 horsepower and being tuned for awesome mid-range, you will experience no lacks of power whatsoever and blowing away the competition will come as standard equipment. I especially enjoyed revving it high when exiting a tight corner and have the rear wheel spin like there’s no tomorrow and it all resulted into a very high and aggressive jump when the obstacle that determined me to accelerate in the first place reached the bike’s wheels.
You can buy the KTM SX-F biggest models displacing either 449.3cc or 477.5cc, but that is just KTM. The 450cc machine is truly competitive and even though mated to a four-speed gearbox, considered by many inappropriate for the models, you will see that the Austrian engineers know exactly what they’re doing because the motocross tracks these days don’t necessarily require a fifth gear so the rider will not have to live with the thought that the fifth gear that he doesn’t change will probably have it taken among the first because he will actually be the first.
If you have doubts about related to the “missing” gear in the transmission you should very well go with the 505 model as it has bigger bore and will have you covered in no time. I also ridden this bike and found that the low and mid-range are even more powerful, with the healthy top-end being present all through the straight line of the track.
Handling these babies is an absolute joy as they can be leaded wherever you wish in a split second. They are light, versatile and real blasts. What could you wish more? It will take you through corners with the greatest ease as the suspensions are incredible and adapt to any type of riding and all that implies corners also.
But the WP suspensions are not only meant to keep you on the right trace of the track and the one indicated by you. When it comes to these bikes, the suspensions soak up bumps and perform incredible on landings so that the finish line would be the rider’s only goal. No matter the speed, height or surface on which you land, no inconvenience such as bottoming out the 48 mm fork will intervene.
Brakes? Wow! When KTM started making a name for itself the maker was best known for producing awesome performing powerful engines and strong reliable brakes. There wasn’t a great deal about the bike’s chassis, but that came with time. Related to the brakes, they only got better and better resulting in great stopping power directed on the Excel wheels through the 260mm front disc brake and 220mm rear disc. It is awesome to push the bike further and further as you know that the brakes will put an end to your adrenaline rush and have you prepared for even another tight corner.
Riders who are searching for something special are offered these two bikes from KTM and they both come at special prices. MSRP for the KTM 450 SX-F is $7,298 while the suggested retail price for the bigger version, the 505 SX-F reaches as much as $7,498.
The Austrians are famous for producing bulletproof blasts that never fade away in front of the competition and the models reviewed today don’t like exceptions. They stand as a true representation of the way KTM builds its racing four-stroke motocross bikes because they are practically KTM’s competition four-stroke SX-F models together with their smaller brother, the 250 SX-F.
Engine and Transmission
Engine type: Single cylinder, 4-stroke
Displacement: 449.3 cc; 477.5 cc on the 505 SX-F
Bore x stroke: 97 x 60,8 mm (3.82 x 2.39"); 100 x 60.8 (3.94 x 2.39") on the SX-F
Compression ratio: 12.5:1
Transmission: 4 gears
Carburetor: Keihin MX FCR 41
Control: 4 V / DOHC; + finger followers on the 505 SX-F
Lubrication: Pressure lubrication
Engine lubrication: 10W50
Primary drive: 29:74
Final drive: 14:52
Cooling: Liquid cooled
Clutch: Wet multi-disc clutch, operated hydraulically
Ignition: Kokusan digital DC-CDI
Chassis and Dimensions
Frame: Central double-cradle-type 25CrMo4
Subframe: Aluminium 7020
Handlebar: Renthal Aluminium, konifiziert; Renthal Aluminium Ø 28/22 mm (1.10/0.87") on the SX-F
Front suspension: WP USD Ø 48 mm (1.89")
Rear suspension: WP Monoshock PDS
Suspension travel front / rear: 300 / 335 mm (11.81 / 13.19")
Brakes, front / rear: Disc brakes 260 / 220 mm (10.24 / 8.66")
Rims, front / rear: 1.6 x 21"; 2.15 x 19" Excel
Tires, front / rear: 80/100-21"; 110/90-19"
Chain: 5/8 x 1/4"
Main silencer: Aluminium
Steering head angle: 63,5°
Wheel base: 1475±10 mm (58.07±0.38")
Ground clearance (unloaded): 380 mm (14.96")
Seat height: 925 mm (36.42")
Fuel capacity: approx. 8.2 liters (2.17 gal)
Weight (no fuel): approx. 104,6 kg (230.6 lbs)