The CFMoto CForce 400 is one of the most popular sport ATV models for trail and off-road riding. This powerful 400cc liquid-cooled engine delivers exhilarating performance on rugged terrain.
But even well-built machines like the CForce 400 can develop some nagging issues over time. In this in-depth article, we’ll outline the 7 most common CFMoto CForce 400 problems reported by owners, along with troubleshooting tips and proven solutions to get you back riding.
Read on to learn how to diagnose and fix frequent problems with the CForce 400 ATV model.
Table of Contents
1. Exhaust Problems
Over time, the exhaust pipe, muffler, or other components can become warped or rusted leading to problems like:
- Abnormal exhaust noise – anything from rattling to loud droning sounds
- Power loss accelerating or at high RPMs
- Backfiring or popping noise, especially when decelerating
If you notice any unusual exhaust noises or symptoms, thoroughly inspect the entire exhaust system including:
- Exhaust pipe
- Exhaust manifold
- All clamps, springs, and hangers
- Heat shields
Exhaust leaks allow pressure to escape, reducing engine performance. Listen for any hissing noise near damaged or warped exhaust joints.
Also check the muffler internals and spark arrestor screen. Excess carbon buildup can block exhaust flow causing increased back pressure.
Replace any visibly damaged or corroded exhaust components. High temperatures combined with moisture and road debris take a toll over time.
Aftermarket slip-on mufflers from reputable brands like Yoshimura or Two Brothers are popular upgrades to replace worn stock mufflers. Choose a muffler specifically engineered for the CForce 400 to get the right fit and sound.
Proper re-torqueing and sealing of all exhaust joints is critical to prevent leaks and restore power. Apply high-temp exhaust sealant to help create an air-tight seal. New exhaust gaskets may also be required if the originals are burned or crushed.
For stubborn exhaust problems, replacing the entire system with an aftermarket exhaust designed for the CFMoto CForce 400 can be the solution. Complete systems with a tuned header and muffler provide maximum flow and power gains.
Taking time to properly diagnose and fix exhaust issues prevents power robbing back pressure. Your CForce 400 will feel peppy and responsive again after addressing any exhaust leaks or blockages.
2. Vapor Lock and Stalling Issues
Vapor lock is another nagging issue that can affect the CForce 400, especially in hot weather riding. Vapor lock occurs when gasoline vaporizes in the fuel delivery system, disrupting the air-fuel mixture flow to the engine.
Symptoms of CForce 400 vapor lock include:
- Hard starting or long cranking before engine fires up
- Stalling at idle after getting hot
- Sudden loss of power under acceleration
- Backfiring or sputtering from fuel starvation
Vapor lock happens as heat builds up in the fuel system from the engine and exhaust. The gasoline starts to boil and evaporate inside the fuel lines, carburetor, and intake tract.
As vapor bubbles form in the system, it disrupts the normal liquid fuel flow to the injectors or carburetor. This leads to symptoms like surging, hesitation, and eventual stalling.
Here are some tips to prevent or treat vapor lock issues on the CForce 400:
Keep the fuel tank full – Running the tank low allows more airflow which contributes to heating and fuel evaporation. Top off when the tank is half empty.
Inspect the vent lines – Make sure the fuel tank vent lines are clear. Any blockage can create excessive vacuum and heat in the fuel system.
Check carburetor float settings – With the carburetor type fuel system, improper float levels can cause flooding which leads to vapor lock.
Consider bypassing the EVAP system – The factory evaporative emissions system adds complexity. Disabling it prevents blockages that can cause vapor issues.
Replace fuel filters – Clogged fuel filters can restrict fuel flow leading to overheating and boiling inside the fuel system.
Use a fuel stabilizer additive – Stabilizers contain antioxidants to prevent fuel breakdown which contributes to vapor lock.
Check air filters – A restricted air filter makes the engine work harder producing excess heat in the fuel system.
Properly inspecting and servicing the complete fuel delivery system is key to resolving stubborn vapor lock problems. Parts like the fuel pump, filters, carburetor, and vent lines may need cleaning or replacement if excessively worn.
Vapor lock can be frustrating, but addressing the root causes allows your CForce 400 to start and run cleanly without issues.
3. Overheating Problems
Given the high-performance liquid-cooled engine, it’s important to monitor engine temperature on the CForce 400. Like any ATV, the CForce can suffer from overheating issues if the cooling system isn’t maintained properly.
Common causes of CForce 400 overheating include:
- Insufficient or dirty coolant – Coolant should be a 50/50 mix of water and coolant. Make sure radiator and overflow levels are correct.
- Damaged or leaking radiator – Inspect for bent fins or leaks allowing coolant to escape.
- Clogged air filter – Restricted air flow prevents proper engine cooling.
- Blocked radiator screen – Clean away bugs, mud or debris blocking air flow to the radiator.
- Stuck thermostat – Test thermostat operation, replace if not opening to circulate coolant.
- Failing water pump – Bad bearings seize the pump impeller preventing coolant circulation.
- Blown head gasket – Compromises the cooling system, allowing coolant leaks into engine.
Monitor your CForce 400’s temperature gauge closely, especially when climbing hills or idling in hot weather. If it creeps above normal range, stop and inspect:
- Check radiator coolant level – Top off if low using the recommended 50/50 premixed coolant.
- Feel the upper and lower radiator hoses – Should both feel hot. If one hose is cold, it indicates blocked flow.
- Check cooling fan operation – Cooling fans should activate once engine is warmed up.
- Test the thermostat – Replace if stuck closed preventing coolant circulation.
- Pressure test system – Checks for internal leaks indicating a blown head gasket or other issue.
Removing debris like mud or grass from the radiator screen is a quick fix to improve airflow and prevent overheating.
For persistent overheating, the entire cooling system may need flushing to remove contaminants blocking flow. Replace any failing parts like the radiator, water pump or thermostat.
With the proper coolant mix and working components, the CForce 400’s liquid-cooled engine can stay reliable and worry-free.
4. Poor Throttle Response
Lackluster throttle response is another common grievance from CForce 400 owners. ATVs need snappy throttle input to handle technical trails.
Symptoms of poor throttle response include:
- Delayed or hesitant acceleration when twisting the grip
- Feeling of weak power on take-off
- Overall sluggishness
Causes for poor throttle response to check include:
- Dirty or clogged air filter – Reduces air intake to the engine.
- Fouled or wrong spark plugs – Incorrect plugs or gap can affect combustion timing.
- Malfunctioning throttle position sensor – Provides inaccurate throttle opening signal.
- Vacuum leaks – Allow unmetered air to disrupt fuel mixture ratios.
- Valve clearance out of spec – Affects throttle response at low RPMs.
Start with inspecting and cleaning the air filter. Clogged filters are a common reason for poor throttle response. Use compressed air and gentle cleaning fluid to prevent damaging the filter.
Install new spark plugs gapped to the 0.6 – 0.7 mm spec recommended for the CForce 400. Quality iridium spark plugs provide improved conductivity and durability.
Inspect all rubber intake manifold boots for cracking or loose clamps. Tighten any loose clamps to prevent unmetered air leaks affecting the fuel mixture.
Check and clean the throttle body bore and throttle plate if carbon buildup is present. Use throttle body cleaner spray and an old toothbrush. Avoid harsh chemicals or wire brushes that damage components.
Finally, check and adjust valve clearance on both the intake and exhaust valves if out of spec. Proper valve lash is critical for throttle response and performance.
Addressing these common factors will help restore the crisp, strong throttle response that makes the CForce 400 so fun to ride in technical terrain.
5. Clutch Related Problems
The CForce 400 uses an automatic centrifugal clutch to engage the belt drive system and rear wheels. This clutch is constantly slipping and grabbing to modulate power delivery. So it’s normal for the clutch to experience wear over time.
Some common CForce 400 clutch problems include:
- Poor take-off power until high RPM
- Sluggish acceleration
- Belt slipping under load
- Burning smell from clutch overheating
Typical signs of a worn clutch on CForce models:
- Reduced acceleration – Takes longer for clutch to fully engage
- Clutch dragging – Has trouble fully disengaging when throttle is closed
Many owners report clutch issues emerging around 500 hours or 10,000 miles – even sooner if riding in wet or muddy conditions.
To restore optimal clutch function on a CForce 400:
- Clean clutch components to remove debris and oil contamination.
- Inspect and replace any excessively worn parts – springs, weights, friction plates, etc. High quality aftermarket clutch kits are recommended for reliability.
- Make sure clutch components move freely on shafts without binding and engage fully when accelerating.
- Check the drive belt condition – replace if cracked or chunks missing which compromises traction.
- Ensure proper deflection adjustment on the belt – Around 16-20mm of play when pressing the lower belt midway between sprockets.
- Grease the splines on the moveable sheave to prevent wear and binding.
The CForce 400 clutch takes the brunt of extreme loads riding over rough terrain. Rebuilding or replacing worn components restores proper engagement and acceleration.
6. Electrical Gremlins
While the CForce 400’s electrical system is generally robust, it can suffer glitches from time to time like any ATV exposed to harsh riding conditions.
Some common electrical issues include:
- Battery dying or not holding charge
- Intermittent power loss
- Instrument or lighting failures
- Starting troubles
Dirty or loose battery connections are a frequent culprit for electrical gremlins. Remove the battery and use a wire brush to clean the battery terminals and cable ends.
Inspect where the black ground wire connects to the engine or frame. Clean any paint, rust or debris from the contact surface to ensure a solid ground.
Check for damaged wiring – rodents love chewing on ATV wiring insulation! Inspect for any chafed or shorting wires and repair. Apply dielectric grease to connections to prevent corrosion.
Verify the battery, stator, and regulator/rectifier are all in good condition. Have the charging system tested to confirm components are properly supplying and regulating current.
On fuel-injected CForce 400 models, inspect throttle position sensor, oxygen sensor, and MAP sensor connections. Clean any corroded pins or terminals. Faulty sensor inputs cause all types of running issues.
Patience and meticulously tracing wiring from components to connectors is key to tracking down CForce 400 electrical gremlins. But paying attention to little details like clean grounds and tight connections keeps the electrons flowing!
7. Braking Issues
The CForce 400 is equipped with dual hydraulic disc brakes offering strong stopping power. However, hard use riding off-road means the brakes take a pounding and require regular service.
Common CForce 400 brake problems include:
- Spongy brake lever feeling
- Loss of braking power
- Excessive lever travel
- Brake fade when hot
- Excessive noise or chatter
Brake pads are a normal wear item. Inspect pads for thickness less than 3mm – time to replace. Also check pad surface for glazing or contamination from leaking fluid.
Sticky or corroded brake caliper pistons can prevent full pad contact with the rotor. Clean caliper internals so pistons can fully retract.
Old brake fluid absorbs moisture over time leading to corrosion and reduced braking force. Flush systems annually with fresh, DOT4 fluid.
Air trapped in the lines causes a soft brake pedal or lever. Bleed the system properly to remove any air bubbles compressing the fluid.
For optimal performance, upgrade to quality aftermarket brake pads like Galfer or EBC. More friction material improves heat resistance and stopping power.
Make sure the brake caliper slides and hangers move freely without binding. This ensures even pad wear without torque twist.
Proper brake maintenance is vital for safe riding. Don’t delay servicing any braking issues on your CForce 400.
The Bottom Lines
While the CFMoto CForce 400 is well-designed and constructed, it can still experience common issues from extensive off-road use like:
- Exhaust leaks robbing power
- Vapor lock causing hot start problems
- Overheating from coolant or radiator issues
- Poor throttle response from worn filters, sensors, etc.
- Clutch problems reducing acceleration
- Electrical issues like battery or sensor failures
- Brake wear decreasing stopping power
Regularly inspecting key components and fixing any issues promptly is the best way to keep your CForce 400 running optimally for miles of trail riding.
Following the factory maintenance schedule and upgrading parts like the clutch, exhaust, and brakes helps maximize durability when riding aggressively.
With the right TLC, the CFMoto CForce 400 provides years of exhilarating performance on the trails. Ride safe and keep the rubber side down!