How Fast is A 85cc Dirt Bike | Dirt Bikes Action

An 85cc dirt bike is amongst the lightest and easiest dirt bikes after 70cc and especially 50cc dirt bikes. It has got 60% more power at least which is ready to provide you and your son a good start in motocross riding. Also, it is one of the major considerations you can have in a motocross dirt bike riding journey. Being a passionate rider, you must be thinking of How fast an 85cc dirt bike is.

Well, you should definitely ask this especially if you are already into a 50cc category or you are now upgrading towards a slightly bigger engine with a bit more power. A typical 50cc is supposed to provide a speed of 25 to 40 MPH or under 30MPH, to be precise. 85cc instead, is supposed to give a range of 30 to 45 MPH max, depending upon a lot of factors that we are just going to discuss. 

There are some 85cc dirt bikes that may hit 65 km speed even but not all out there are going to hit this speed. Most will do 50 or 55 km/h max despite having a top metered speed of 65 except for one model that can even hit the 80 km/h limit. However, this depends on the type of fuel you put in, tire pressure, road type, terrain, weight, the weight of the bike itself and also a couple of other things.

See Also: How fast is a 50cc Dirt Bike

How Fast is A 85cc Dirt Bike

An 85cc dirt bike manufactured by a good brand features 2 stroke engine with a good fuel mix-up and the best riding techniques with proper gear and track is going to be a fast thing with a top speed range of 50 to 80 km/h. It is about 30 to 45 or 50 miles per hour. How fast an 80cc dirt bike goes technically depends on the amount of mechanical and chemical stress you put on it. You can even find 85cc dirt bikes with a top speed of 80 miles per hour even, like the KX85 of Kawasaki.

If you can maintain your bike well, ride it carefully, and load it up with a nice kind of fuel with the proper mixup, it can go as fast as 85 km/h. Now, you will not achieve this speed every time on every kind of 85cc. Instead, it’s achievable on limited and specific bikes and that too with proper practice. There are a lot of technical things involved, let’s take a look at them. Then we will explore some of the best 85cc dirt bikes and common questions about these bikes.

Factors Affect How Fast is A 85cc Dirt Bike

Well, there isn’t any general rule of thumb about how fast an 85cc dirt bike is or what its top speed is. This all depends on technical stuff like your engine type and health, how well you maintain it, what’s the weight of your dirt bike, how much weight you carry, what riding gear you prefer, where you ride your dirt bike at and things like tires, braking, acceleration, de-acceleration and some other sort of things.

  • The Engine of Dirt Bike

The engine is undoubtedly “The most important part of your dirt bike” and there is no exception. Everything happens due to this and your bike moves fast or slow is also due to that hot metallic box. Now the engine itself has some kinds and every kind of engine has a different technology and incorporated design to make it work. 

That’s why an engine of the same capacity but on multiple bikes creates a huge speed difference. The working of an engine is what makes it a beast, better or worse than others in the league. I usually prefer dirt bikes with Power Valves system in their engines as it provides a power boost by optimising the engine RPM through the crank, leading to a fast speed out there on the track. This usually comes with Yamaha bikes and you will also get this thing in Yamaha YZ85.

Besides this, the valves and cylinder design with their right positioning in the engine matters too. Engines with cylinders that are horizontally placed inside give a smooth ride and can also be pushed to boost the speed nicely. That’s a very useful thing in dirt bikes especially when you are on uneven terrain and need a good speed too. To cool down that entire system, the engine should come equipped with water or liquid cooling so it does not heat up instantly on a hat day out.

Now, we’re not going to be in thermodynamics of a bike as this isn’t the goal here. Other than these things, there is a concept of 2 and 4 stroke engines. If you want your 85cc bike to run fast, you should prefer 2 stroke light body engines as they work quite better and provide a good speed. Most motocross dirt bikes you will get might feature a 2 stroke engine. They are quick though but noisy as well.

For a good speed and long-lasting engine, you should prefer a dirt bike with a 5 or 6 speed transmission as it nicely shifts the loads on different and additional gears to ensure a good journey. With this touch along with 2 stroke engine and proper valves with a cylinder, an 85cc dirt bike might be able to produce 18 to 27 horsepower which is a pretty good deal for this engine capacity as well as for you.

  • Bike Weight and Load Capacity

The total weight of your bike’s body, the fuel it’s carrying along with your weight and additional gear or stuff (if you are carrying along) will also change the speed limit. It’s simple physics basically. When a cart is full of load, it will be difficult to move or you can’t push it to go and touch its speed limit. Instead, you need to have less weight on that cart if you want to push it hard and fast.

Now for the dirt bike, since it is a machine, things might be slightly different. Your bike can still go fast even if you have loaded to its full carrying capacity. However, it would be just half as normal. For example, if your bike was supposed to do 80km/hr with its and your body weight, it will now hardly reach 50 km/h speed with a carrying load of around 100 or 150 additional pounds. It is 68kg!

The 85cc dirt bike itself weighs around 140 to 165 pounds in total, obviously with an empty fuel tank. But this weight is also not identical as it may vary from brand to brand as different technologies and materials are used to manufacture that particular machine. Yamaha YZ85 for example weighs 160 pounds, the Kawasaki KX85 weighs slightly more which is 165 pounds. Honda CR85R is light comparatively with a weight of 155 pounds. The same weight they can carry too.

  • Age and Height Of The Rider

Well, this might not be the direct thing that affects the speed of a bike, but I think so! With the age and height of a rider, a bike may or may not speed to its limits. This may not be a count for the heavy engine capacity dirt bikes of 250cc and beyond, but it matters for under 150cc (especially 100cc) as they are designed as mini dirt bikes for kids. And, sometimes they are solely for kids and not for adults.

For example, PW50 is a nice 50cc mini dirt bike for kids by Yamaha and it is solely meant for kids. Now, imagine an adult of 5 feet riding on it would definitely make no sense at first, and secondly, it would just slow down the speed and nothing. So, we will cover this age to height ratio for the kids first.

As 50cc is a good size for kids up to 8 years, 70, 80 and 85cc dirt bikes are ideal choices for kids ranging an age of 9 to 11 years old. Though I would stick to 9-10 only, let’s just push it a little beyond the 11-year kids. Now, in some cases, you would disagree with the age factor as every kid has his own growth and it could be different from others. So, it’s better to take a seat height chart for this.

For kids with a height of 4.5F or 140cm which is normal for good growth, you should consider buying a dirt bike with a seat height of 24 to 26 inch. Unfortunately, you would hardly get a 85cc dirt bike with this seat height for kids. So, I would strongly recommend PW50 with a seat height of 18 inches or SSR SR70C with a seat height of 22.5 inches which is a 70 cc 4 stroke and 4 speed dirt bike.

With 141 to 158cm height, you should get a 31 to 35 inch seat height and it’s usually available as well. You can choose from Yamaha YZ85, Kawasaki KX85, Husqvarna TC 85, Suzuki RM85L and CR85R of Honda. For a height of 158 to 172cm, you should opt for a seat of 34 to 38 inches. TM85x and KTM 85 Sx are your bikes.

  • Terrain & Experience

Well, it’s true. What terrain you are riding on and what experience you have got with that train along with that particular bike also play a role in making your bike fast and smooth. You are supposed to ride your dirt bike on off road tracks. Here, you might deal with sand, mud, rocks and forest sort of areas.

The place and terrain your drive slows or fasts your bike’s speed. For example, the speed would be low in the mud, a bit more on the sand and fast on rock, forests and ground. Technically, your bikes are going to be faster on terrains that are flat with rocks and mud. On the hilly areas, slopes and muds, your bike will be slow. This also depends on your skill and how you manage to ride out your machine.

  • Tire Pressure, Braking & Acceleration

These things like how much PSI you put in your dirt bike, how you accelerate, and how you shift between gears and your brake affects your bike’s performance, power and speed too. If you want to hit the top speed, you should make sure to keep tires in a range of 8 to 18 PSI max, depending upon type of track.

As soon as you want to gain speed, you need to accelerate but that should too in a nice way to get the best out of the engine’s power to boost your speed. While you are shifting, make sure you use the clutch properly and it engages with the gear truly that you can ensure by pulling the lever completely. Also, when you need to shift or slow down your bike, shift downwards after applying brakes. Don’t push the accelerator too hard and the brakes should be heavy.

  • Bike Maintenance & Brands

If you have got a nice machine and it is moving fast, you need to ensure it keeps going in the same way. You can do this by maintaining your bike properly and getting your bike serviced at the right time. First, refer to your bike’s manual and change the gear and engine oil at recommended time and use good quality or grade oil. Don’t go for the cheaper ones, it will just ruin your engine in the long run.

Tune up your bikes carefully, and change the oil and air filter on time it must be on time especially if you are used to speeding your dirt bike as per its limits. Lubricate everything from the chain, to the sprocket and also use a nice kind of fuel with proper oil mixup in a fixed ratio if it’s a two stroke engine. Just take care of it and it won’t stop.

How Fast is A 85cc Dirt Bike | Frequently Asked Questions

  • How Fast Does A 85cc 4 Stroke Dirt Bike Go?

A 4 stroke 85cc dirt bike moves faster and it can have an average top speed of 40 to 45 mph. A 4-stroke dirt bike has a different ignition cycle but it provides better control to the rider compared to a 2 stroke dirt bike. However, it is not very fast but features a little silent engine which is the opposite case in 2 stroke dirt bikes.

  • How Fast Does A 85cc 2 Stroke Dirt Bike Go?

A 2 stroke 85cc dirt bike is considered and actually a fast machine with an average top speed touching 50 mph or 80 km/h in a limited and particular dirt bike. 2 stroke is a bit more aggressive and has a faster engine than 4 stroke and it will always be faster than a 4 stroke engine with similar capacity. If you have some experience riding a dirt bike, you should opt for a 2 stroke engine but 4 stroke is easier than it.

  • How tall should you be for an 85cc dirt bike?

You should be having at least 140 centimetres or 4 feet and 6 inches of height for an 85cc dirt bike. If you are having a height of up to 140cm, you should be using an 85cc dirt bike with a 24 to 26 inch seat height. 24” would work nicely and if you are a bit less than that, you can even use a 22.5 inch height seat. Ideally, you should be at least 4.5 feet. Otherwise, your feet are not going to properly hit the floor.

  • What age is an 85cc dirt bike for?

If there is a kid, an 85cc dirt bike would be ideal for 9 to 10 year old kids either boy or girl. However, with the seat height and tire size, you will be able to know this. A 16 inch to 19 inch alloy rim would be a nice size for an adult too.

  • How Much Is A 85cc Dirt Bike?

This entirely depends on the model, make and most importantly the brand of that 85cc dirt bike. Generally, dirt bikes with this engine capacity start from a thousand bucks but that’s up to your luck. Ideally, it would start from CR85R & CR85RB starts from $2,800 to $2,900 while the highest you would pay is $7000 for KTM 85X. Yamaha’s YZ85 would cost under $5000.

  • What Is the Fastest 85cc Dirt Bike?

KTM85x is currently the fastest dirt bike of the league that can easily surpass 70 mph which is around 110 km per hour.

  • How to Increase the Speed of an 85cc Dirt Bike?

You can increase the speed of your dirt bike by maintaining the parts of your bike. Keep changing air and oil filters, use A grade engine oil, mix the fuel with a 40 to 60:1 ratio, always use high octane fuel, and maintain a good and healthy PSI pressure. This is what you can do for your bike and tune things on time.

  • How Fast Does A YZ85 2 Stroke Go?

YZ85 is a 2 stroke dirt bike and it has a nice power valve system providing a fast response of up to 65 miles per hour which is slightly above 100km/h speed. Although you might not necessarily achieve full speed (unless you maintain your bike and ride with skills), you can still hit 80-90 km/h speed easily.

  • How Fast Does A KTM85 Go?

KTM85 has a speed of 70 miles per hour or 110 kilometres per hour making it the fastest bike under the 85cc dirt bike category.

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