So, you want to know how to make your Honda Fourtrax 300 faster? That trusty 300cc workhorse has plenty of torque, but sometimes you just need a bit more speed for the trails or the open fields. The good news is, there are several proven ways to wake up that engine and improve your machine’s performance without breaking the bank. This guide will walk you through the best modifications, from simple bolt-ons to more involved engine work, so you can get the most out of your ATV.
How Can I Make My Honda Fourtrax 300 Faster
This is the core question we’re answering. Gaining speed on a Fourtrax 300 involves a combination of improving airflow, adjusting fuel delivery, reducing weight, and sometimes changing internal components. It’s a system, and each mod you do often supports the next. We’ll start with the easiest and most affordable tweaks and move towards the more complex projects.
Start With Maintenance: The Foundation for Speed
Before you spend any money, make sure your ATV is running at its absolute best. A poorly maintained machine will never be fast, no matter what parts you bolt on.
- Fresh Spark Plug: A new, correctly gapped plug ensures a strong, clean burn.
- Clean Air Filter: A dirty filter chokes the engine. Clean or replace it. Consider switching to a high-flow foam filter.
- New Oil and Filter: Clean oil reduces friction and protects vital engine parts under higher stress.
- Check Valve Clearance: Out-of-spec valves rob power. Adjusting them to factory specs can make a noticeable difference.
- Proper Tire Pressure: Over-inflated tires can reduce traction, while under-inflated ones create drag and affect handling.
Exhaust System Upgrades
The stock exhaust is designed for quiet operation and emissions, not maximum power. Replacing it is one of the most effective first mods.
- How it Helps: A less restrictive exhaust allows spent gases to exit the cylinder faster and more completely. This lets the engine breathe better and can produce more power across the RPM range.
- What to Look For: A full aftermarket exhaust system (header and silencer) will offer the best gains. Slip-on mufflers are cheaper but offer smaller improvements.
- Note: A new exhaust often requires re-jetting the carburetor to add more fuel for the increased airflow.
Carburetor Re-Jetting and Airbox Mods
More air needs more fuel. When you change the intake or exhaust, you must often adjust the carburetor’s jetting to match.
- Open the Airbox: A simple, free mod is to remove the airbox lid or snorkel. This lets more air in. Be cautious of deep water, as it makes ingestion more likely.
- Re-Jet the Carb: This is crucial after an exhaust or airbox mod. You’ll typically need a larger main jet and possibly a larger pilot jet. Kits are available specific to the Fourtrax 300.
- Fine-Tuning: Adjust the fuel screw and needle clip position based on how the engine runs. A slight bog or pop on deceleration are signs you need to tune further.
Consider a High-Flow Air Filter
Pair your airbox mod with a reusable foam filter from a brand like Uni or K&N. They flow better than the stock paper filter and can be cleaned and oiled for years of use. Just make sure you maintain it properly to avoid dirt getting into your engine.
Ignition Advance and CDI Box
The stock ignition timing is set conservatively. Advancing it a few degrees can improve throttle response and power.
- Manual Advance: You can physically rotate the stock stator plate a few millimeters to advance the timing. This is a low-cost trick but requires precision.
- Aftermarket CDI Box: A performance CDI (Capacitor Discharge Ignition) often increases the rev limit and provides a more aggressive spark curve. This lets the engine rev higher and make more power. Be careful not to over-rev the engine, as these motors have limits.
Weight Reduction and Gearing
Power is only half the equation. Making the ATV lighter or changing its gearing makes better use of the power you have.
- Remove Unnecessary Parts: Take off the front and rear racks if you don’t use them. Every pound counts.
- Lighter Tires/Wheels: Heavy, aggressive mud tires sap power. Switching to lighter aluminum wheels and less aggressive trail tires can improve acceleration.
- Sprocket Changes: This is a huge one. Swapping to a smaller front sprocket (1 tooth smaller) or a larger rear sprocket (2-4 teeth larger) will give you much better acceleration and low-end pull, though it reduces top speed. For more top speed, do the opposite.
Internal Engine Modifications
For the most significant gains, you’ll need to open up the engine. This is where costs and skill requirements increase.
Big Bore Kits
The most popular internal mod. A big bore kit replaces the cylinder and piston to increase displacement, say from 300cc to over 350cc.
- More displacement means more air and fuel per combustion cycle, which translates directly to more torque and horsepower.
- Kits from companies like Powroll are reliable and come with everything needed.
- This mod almost always requires a carburetor re-jet and benefits greatly from a performance exhaust.
High-Compression Piston
Even without increasing displacement, swapping the stock piston for a high-compression version squeezes the air-fuel mixture tighter, creating a more powerful explosion. You may need to run higher-octane fuel to prevent knocking.
Camshaft Upgrade
A performance camshaft changes how long and how far the valves open. This optimizes airflow at higher RPMs for more top-end power. It’s a great companion to a big bore kit and requires careful valve adjustment.
Putting It All Together: A Sample Build Path
Here’s a sensible, staged approach to modifying your Fourtrax 300 for more speed.
- Stage 1 (Basic Bolt-Ons): Perform all baseline maintenance. Install a high-flow air filter and a full aftermarket exhaust system. Re-jet the carburetor to match. This is the essential foundation and will provide a very noticeable improvement.
- Stage 2 (Ignition & Gearing): Install an aftermarket CDI box to raise the rev limit. Change the front sprocket to one tooth smaller for snappier acceleration. Reduce any unnecessary weight.
- Stage 3 (Engine Work): Install a big bore kit (e.g., 330cc or 350cc). Pair it with a high-compression piston and a performance camshaft. You will definately need to re-jet the carburetor again, possibly with larger jets than before.
Important Considerations and Cautions
More power and speed means more stress on your ATV. Keep these points in mind.
- Clutch Wear: Increased power can wear the stock clutch faster. Be prepared to upgrade to heavy-duty clutch springs or a full clutch kit.
- Cooling: A hotter-running engine may need help. Ensure your cooling system is clean. In extreme cases, an aftermarket oil cooler can be added.
- Brakes and Suspension: Going faster means you need to stop and handle better. Make sure your brakes are in top shape and consider suspension upgrades if you’re riding aggressively.
- Reliability: Pushing an engine beyond its original design can affect its longevity. Proper tuning and maintenance are more critical than ever after modifications.
Frequently Asked Questions (FAQ)
What is the cheapest way to make my Fourtrax 300 faster?
The cheapest ways are maintenance (fresh plug, clean filter), removing the airbox lid, and changing the sprockets. A sprocket change, especially a smaller front sprocket, gives a huge perceived gain in acceleration for very little money.
Do I need to re-jet after putting on a new exhaust?
Yes, almost always. The increased airflow leans out the fuel mixture, which can cause the engine to run hot and lose power. Re-jetting is a necessary step for both performance and engine safety.
How fast can a modified Honda Fourtrax 300 go?
A stock Fourtrax 300 might reach 50-55 mph. With full bolt-ons (exhaust, jetting, CDI), you might see 60-65 mph. With a big bore kit and other internal work, some builds can approach or slightly exceed 70 mph, depending on gearing and weight.
Is a big bore kit hard to install?
It requires mechanical skill. You need to remove the engine, split the cases, and replace the cylinder and piston. If you’re not comfortable with this, have a professional mechanic do the installation. A mistake here can ruin your engine.
Will these mods make my ATV less reliable?
If done correctly and tuned properly, reliability can remain very good. However, pushing any engine harder will increase wear on components like the piston, rings, and clutch. Regular maintenance becomes even more important.
Can I just install a performance CDI box by itself?
You can, and it will raise the rev limit, but the gains without other mods are minimal. The CDI box works best when the engine can actually breathe better through intake and exhaust upgrades to take advantage of the higher RPM range.
Making your Honda Fourtrax 300 faster is a rewarding project that can breath new life into a classic ATV. Start with the simple, affordable mods and work your way up as your budget and skills allow. Always prioritize proper tuning and maintenance to ensure your faster machine is also a reliable one. Remember to ride responsibly and wear your saftey gear, as the increased performance will change how your ATV handles.