Dirt bikes have come a long way in the last few decades, with increases in performance all around. Cornering, throttle response, outright max speeds and acceleration are all so much more superior.
They’re certainly getting damn fast too! Especially 450cc dirt bikes which is the most popular bike of choice for enduro and recretional riding for riders over 80kg.
450cc dirt bikes will get up to around 90 miles per hour or 150km/h before reaching the redline. This top speed is due to the gearing teeth, gearbox restrictions, terrain ridden and the aerodynamic restrictions that most dirt bikes have.
They aren’t really designed to sustain these high speeds for long periods of time in most cases. That said – Dakar Rally bikes are typically 450cc and you see these going seriously fast through the dessert. This is because they have extensive modifications to reduce bottlenecks in performance, paired with an adventure fairing which makes the rider more aerodynamic.
For most riders who are riding their general forest tracks and fire trails, such high speeds are unlikely to be seen.
Factors that Influence 450cc Dirt Bike Speeds
If you take 10 riders and put them on 10 different 450cc dirt bikes, they won’t all reach the same speed. Some will max out much earlier than the upper limit of 90 miles per hour on the dirt.
Why? There are several factors that influence how well someone will achieve these flat terrain results. These are:
- 4-Stroke vs 2-Stroke. Generally, 4-strokes do perform better at higher speeds whereas 2-strokes are best for motocross racing. Yet the 4-stroke is a little heavier as there are more parts inside the engine to make it fire.
- Brand of the dirt bike. A premium brand like KTM will blitz most other bikes most easily and they have the most amount of performance modifications to use. That said, they’re also might expensive too! Honda, Yamaha, Kawasaki, Husqvarna, Gas Gas and Suzuki are only just behind.
- Weight of the dirt bike. A heavier dirt bike is just going to struggle to reach such speeds. Then again, some of that weight might be performance gear designed to help it overtake the competition and win that podium position.
- Wind drag. If you’re heading into the wind, then you’ll probably top out much sooner than the rider with a tailwind. A side wind can influence this too but it plays on the confidence of the rider more than reducing speed.
- Rear sprocket. If you go to swap around for a smaller rear sprocket and a bigger sprocket on the front, then you’ll sacrifice some acceleration yet easily pull a few extra miles out of the top end. This does kill any chance of beating those gnarly hill climbs or beating anyone at a drag race.
- The height and weight of the rider. If you’re weighing quite a bit, then this additional weight does slow the bike down obviously. If you’re a taller rider, then you’ve got more body area that needs to push through the wind. Shorter and lighter riders are more likely to win any speed records.
Then there is the little stuff like excess plastics, the amount of fuel left in the tank and how much tread is left on the tyres. While small, these do play a part.
Top Speeds aren’t the goal
Sure, you might be impressed by getting yourself up to almost 100 miles per hour on the dirt, but this is seriously dangerous and in the realms of the most experienced enduro competitor. In the real world, dirt bikes aren’t designed for this and are really built to have fast acceleration and the ability to get through gnarly tracks.
If you’re in the market for a dirt bike today, then don’t buy one simply because the salesman sales it goes fast. What you’ll want is a bike that you can still throw around and breezes through the corners paired with excellent suspension and solid control.
Road-based motorcycles are better suited for claiming top speed records than dirt bikes. If you still want the feeling, then a dual-sport bike like the KTM990 could be exactly what you need to get your thrill. It has a seriously good adventure fairing and makes for the perfect adventure motorcycle that’s at home on the dirt roads as much as it is on the highway.
Enjoy dirt bike riding for what is and realize that even at 50 miles per hour, that’s seriously enough to bring a smile to your face. And it’s seriously enough speed to land you in hospital for life too. Ride for long enough and you’ll realize that aiming for these fast speeds aren’t the end goal.