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Have you ever ever been curious how briskly a 250cc dust bike can go? Nicely after some testing I’m able to reply your query.
Whereas max velocity will differ barely primarily based on the kind of engine, a 250cc dust bike will are available in between 70-78 miles per hour. 250cc 2-strokes will probably be sooner than 240cc 4-strokes, however solely by 5-10 miles per hour.
There’s a lot that goes into max velocity, and we’re going to dive into all of these causes in addition to methods to extend it.
Engine Stroke
Grime bike engines are available in two totally different sorts of strokes: the two-stroke and the four-stroke. Due to the way in which they’re constructed and the way in which they perform, each has totally different “specialties” that have an effect on acceleration, high velocity, and a number of different variables.
Two Stroke Engines
Two-stroke engines are the a lot easier engine of the 2 choices. They’re designed to finish their engine cycle in two piston actions, as an alternative of 4, just like the four-stroke.
The 2-stroke engine begins its cycle with an influence stroke. The ignited air, gas, and oil combination power the piston down till the combination reaches the exhaust port, a gap on the aspect of the cylinder. The piston travels downward, and it pressurizes the air, gas and oil combination that was beforehand drawn into an attachment on the aspect referred to as a “crankcase”. The combination was pulled into the crankcase throughout the newest compression stroke, the one previous to the present energy stroke that hasn’t accomplished but.
An uncovered consumption switch port lets the subsequent air and gas combination into the cylinder, proper because the crankshaft begins its subsequent rotation, pushing the piston again up. This motion blocks off the exhaust and consumption ports, enabling the piston to compress the gas and air combination. The upward motion of the piston pulls within the subsequent gas and air combination from the carburetors and retains it beneath the piston. The at present compressed air and gas “cost” above the piston is ignited by a spark plug, and the entire thing repeats itself, again and again.
This operation produces much less waste than a four-stroke engine of comparable or equal energy output. They’ve a extra environment friendly construct, enabling them to be assembled and maintained utilizing thirty to fifty % fewer shifting components than a 4 stroke. Two strokes are the simplest of the 2 kinds of engines to wash. They do, nonetheless, have elevated gas consumption, and due to the way in which the stroke of the engine works with the openings within the chamber, it produces extra emissions.
Because of the consumption and exhaust ports being open on the identical time, with every piston rotation a portion of the air and gas combination escapes out the exhaust port with out getting used to energy the engine. That being stated, direct injection and catalytic converters are the exceptions to these guidelines and can scale back the variety of unburned hydrocarbons in your emissions.
Because of the means they’re assembled, they require gas and oil combination. Two-stroke engines typically require extra upkeep, however the components are cheaper. Bikes with two-stroke engines are typically lighter and sooner, with extra of an preliminary kick to the “stand up and go”. Whereas they require half the strokes to perform the identical goal as a four-stroke engine, they do make twice as a lot noise. Two-stroke engines gives you extra torque at the next RPM.
4 Stroke Engines
A four-stroke engine takes 4 piston actions to attain a singular engine cycle. On the primary, or “consumption” stroke, the piston lowers, pulling in a combination of air and gas. Subsequent, it raises for the “compression” stroke, which ignites the air and gas combination. This ignition forces the piston down for the “energy” stroke, adopted instantly by the “exhaust” stroke, pushing the exhaust out of the engine. These cycles repeat again and again, the entire time the bike is operating.
4 stroke engines “hearth” each two revolutions of the crankshaft, which delivers a steadier and extra simply managed output of energy. Usually a greater bike for newbies, a four-stroke engine is nice for each path driving and racing. When path driving on a four-stroke, you’ll not often trip above second gear, as a result of they’ll rev larger than a two-stroke can.
This implies much less be just right for you and your engine. There are extra components to a four-stroke engine, which lets you spend much less time braking and shifting your bike when it’s important to decelerate.
Upkeep is required a lot much less continuously for the reason that work the engine is doing has been unfold out by means of extra components. Sadly, this additionally implies that when upkeep IS wanted, it’s typically costlier, since extra components should be labored on and changed. These extra components additionally make bikes with four-stroke engines heavier than their two-stroke counterparts.
4 stroke engines are a really clear burning engine from the point of view of emissions testing. It is because they’ve the next gas effectivity than the two-stroke engine, and also you don’t have to combine oil along with your gas in an effort to make the engine run.
4 stroke engines are heavier, which ends up in a heavier bike when related cubic centimeters are involved, generally weighing 50% greater than comparable two-stroke engines.
They’re additionally a lot more durable to wash, because of the larger variety of components they’re constructed of. 4 stroke engines gives you extra torque at a decrease RPM.
The Rider
Generally, in spite of everything, you are able to do to your bike, your the one which may want an “improve”. You’ll have the most effective, latest, most costly mannequin of dust bike on the market, however for those who don’t know use it, you aren’t going to have the ability to use it to it’s fullest potential.
Your Weight
As painful as that is to handle, your weight goes to have an effect on how briskly your bike is ready to go. Now actually, it typically will solely have a derogatory impact in your expertise for those who’re racing in a straight line. The method can have way more of an influence in your driving expertise than your weight will for those who’re racing on a path or a dust bike monitor. That being stated, weight does make some distinction, irrespective of the way you have a look at it, even when it isn’t all the time going to be the deciding issue.
Your Ability
Like I discussed beforehand until there’s an extremely giant disparity in weight between you and the opposite riders (of their favor), talent goes to be the deciding issue, not your unlucky quick meals habits. So ensure you’re getting in your follow! You could possibly trip your dust bike with out falling off, however that doesn’t imply you’ve got any sort of talent outdoors of fundamental stability, and data adequate sufficient to get your bike’s engine operating.
What do it’s good to do to get higher you ask? Nicely, like several mom who has ever tried to make her little one study the piano will let you know, PRACTICE! The follow could not make you excellent, however it does make progress, and sufficient of it could even make you proficient. Are you practising for a race? See for those who can follow on the monitor. Need to be sooner on the mountain trails you and your buddies frequent? You’ll have to make some additional runs.
After you have issues down like shifting, braking, leaning into turns, and realizing what it’s like to essentially transfer along with your bike, issues develop into extra of an intuition and a response, relatively than an motion that requires aware thought and determination making earlier than you possibly can determine in your subsequent transfer. These choices could solely take you break up seconds, however typically occasions break up seconds are the one variations between first place, second place, third place, and never inserting in any respect.
The Bike
Whereas enhancing your self is a essential and sometimes ignored a part of enhancing velocity and your general dirtbike expertise, there are additionally alterations that may be made to your bike as nicely.
Weight
That’s proper, we don’t discriminate right here. There’s a risk that you just AND your bike could possibly lose just a few kilos. Keep in mind, since we’re speaking about weight, dust bikes with two-stroke engines are all the time going to be lighter than their four-stroke counterparts. So if weight is what you’re eager to concentrate on, make sure that to maintain that in thoughts.
Now, to be clear, these should not suggestions. I’m going to offer you concepts and examples of make your bike lighter primarily based on my expertise and the experiences of others, however ensure you do your analysis and are accountable with the alterations you make to your bike. Simply since you can do it doesn’t imply that you just ought to. Structural stability ought to all the time be maintained.
- Lighter tires – Will this make a HUGE distinction when slicing down weight? Most likely not. But when you can also make plenty of little adjustments, the load you’re subtracting out of your bike will begin to add up. In a great way. You may as well not add tire mousse or tire slime to your tires. Does this include some inherent danger? Sure. However so does driving your bike typically.
- A lighter seat, or a lighter seat cowl – There’s an above common likelihood that the seat you’re utilizing is the one your bike got here with. There’s nothing flawed with that, however for those who’re trying to lower down weight, it is a good space to do it. Not solely will it not affect the mechanics of the bike, however you would possibly truly even discover one thing extra snug than what you’ve been utilizing.
- Your plastics equipment – Like your seat, for those who’re nonetheless utilizing the plastics that got here on the physique of your bike whenever you purchased it, there’s a great likelihood there are lighter choices on the market. Along with that, not solely are you able to discover a lighter choice, however there are dust bike plastics kits which can be made with aerodynamics in thoughts. Not solely will you be reducing weight off your bike, however you’ll be enhancing the form, which can assist you to in all areas of your driving expertise.
- The exhaust – This one will probably be fairly spendy, however it’s probably the most efficient methods to take some weight off your dust bike. A dust bike exhaust system is often made out of aluminum or stainless-steel, and whereas they’re robust, they don’t seem to be gentle. A titanium exhaust system will take fairly a little bit of weight off your bike, sadly, it’ll additionally take fairly a bit out of your pockets.
Gearing
Gearing is an alteration you can also make to your bike that doesn’t actually influence the load of the bike, however relatively the acceleration or high velocity of the bike. That is accomplished partly by serving to your bike maximize grip by altering tire rotation to attain the most effective velocity.
As this can make a distinction in how your bike shifts, please watch out and do your analysis, or have somebody assist you to who has earlier expertise altering out the gears on a dust bike. You don’t need to do one thing flawed and burn out your engine, break a sequence, or strip one among your components.
When you’re altering out your gears, you’re going to be altering what’s referred to as your “gearing ratio”. For instance, in case your rear sprocket has 40 “enamel”, and your entrance sprocket has 10 enamel, you’re going to have a gearing ratio of 4. 4 rotations within the entrance for each singular rotation within the again.
Try this video for a extra visible clarification:
| Gear Tooth | 10 | 11 | 12 | 13 | 14 | 15 |
| 60 | 6.00 | 5.45 | 5.00 | 4.62 | 4.29 | 4.00 |
| 59 | 5.90 | 5.36 | 4.92 | 4.54 | 4.21 | 3.93 |
| 58 | 5.80 | 5.27 | 4.83 | 4.46 | 4.14 | 3.87 |
| 57 | 5.70 | 5.18 | 4.75 | 4.38 | 4.07 | 3.80 |
| 56 | 5.60 | 5.09 | 4.67 | 4.30 | 4.00 | 3.73 |
| 55 | 5.50 | 5.00 | 4.59 | 4.23 | 3.92 | 3.67 |
| 54 | 5.40 | 4.91 | 4.50 | 4.15 | 3.85 | 3.60 |
| 53 | 5.30 | 4.82 | 4.42 | 4.07 | 3.79 | 3.53 |
| 52 | 5.20 | 4.73 | 4.33 | 4.00 | 3.71 | 3.47 |
| 51 | 5.10 | 4.64 | 4.25 | 3.92 | 3.64 | 3.40 |
| 50 | 5.00 | 4.55 | 4.17 | 3.85 | 3.57 | 3.33 |
Increased High Pace Threshold
The next high velocity threshold is precisely what it appears like. You’ll be capable of attain larger high speeds, however it’ll come on the expense of preliminary acceleration.
When you’re in search of larger high velocity, you’re going to wish to vary out your present sprocket setup for a bigger sprocket within the entrance or set up a smaller sprocket within the again. You’re primarily going to be doing the precise reverse of what you’ll need to do for those who have been making an attempt to go for sooner acceleration.
What you’ve got now is named a “larger gearing ratio”. You’ll make this transformation to your dust bike if you’re planning on driving within the desert, or sandy areas and arenas. When you’re racing in largely straight traces or doing plenty of driving in locations the place you aren’t making many tight turns, and also you’re capable of truly open up your bike for some velocity, the next gearing ratio could be a great determination so that you can make.
Quicker Acceleration
Having a fast “stand up and go” can provide the edge in fairly just a few conditions you might end up in because the proprietor of a dust bike, particularly for those who’re actually sufficient in velocity to begin altering your bike for particular units of circumstances.
If sooner acceleration is what you’re capturing for, you’re going to need to change your entrance sprocket with one thing smaller, or your rear sprocket with one thing bigger. You’ll need to gear your bike this manner for those who see your self doing monitor races the place you’re making plenty of turns, mountain biking on tighter trails, conditions the place you’re going to wish an edge in brief bursts of velocity, however not a protracted, straight shot. This creates a decrease “gearing ratio”.
