1987 Honda Fourtrax 350 Fuel Pump: Complete Guide to Symptoms, Diagnosis, and Replacement
Why the Fuel Pump Fails on the 1987 Honda Fourtrax 350
The 1987 Honda Fourtrax 350 uses an in-tank electric fuel pump that draws fuel from the bottom of the tank and pushes it to the carburetor at low pressure. Over time, several factors cause these pumps to wear out:
Ethanol damage. Modern gasoline contains up to 10% ethanol, which is corrosive to the rubber seals, diaphragms, and internal components of older OEM pumps. Ethanol also attracts moisture, leading to rust and debris inside the tank that clogs the pump strainer .
Age and wear. The internal brushes and commutator in the electric motor wear down after decades of use. A pump that has been running for 35+ years is simply nearing the end of its design life .
Contaminated fuel. Dirt, rust, or water in the fuel tank can clog the pump's inlet strainer or damage the pump's internal impeller, reducing flow and pressure .
Low fuel level operation. Running the tank consistently below one-quarter full can cause the pump to overheat, since the fuel surrounding it acts as a coolant. Overheating accelerates motor wear and can cause the pump to seize .
Symptoms of a Bad Fuel Pump on a 1987 Fourtrax 350
If your Fourtrax 350 is showing any of these signs, the fuel pump is likely the culprit:
Hard starting or no start. The engine cranks but won't fire, or it takes many seconds of cranking before it catches. This happens because the pump isn't building enough pressure to push fuel to the carburetor .
Engine sputters or surges at high RPM. When you open the throttle, the engine hesitates, stumbles, or loses power. This is a classic sign that the pump cannot keep up with fuel demand under load .
Loss of power on hills or under load. The Fourtrax 350 may run fine on flat ground but struggle or stall when climbing a hill or carrying a load. The pump fails to maintain pressure when the engine needs more fuel .
Whining or buzzing noise from the fuel tank. A healthy pump makes a quiet, steady hum. A loud whining, buzzing, or screeching sound indicates the pump bearings are worn or the impeller is hitting the housing .
No priming sound when the key is turned on. On most Fourtrax 350 models, you should hear a faint two-second buzz from the fuel tank when you turn the key to the "ON" position. If you hear nothing, the pump is not getting power or has failed internally .
How to Diagnose the Fuel Pump on a 1987 Fourtrax 350
Before buying a new pump, you should confirm the old one is actually bad. Here is a simple diagnostic procedure:
Check the fuse and relay. Locate the fuel pump fuse in the fuse box and inspect it for a blown element. Also, check the fuel pump relay by swapping it with a known-good relay of the same type. If the pump starts working, the relay was the problem .
Listen for the prime. Turn the key to "ON" and listen near the fuel tank cap. If you do not hear a two-second whirring sound, the pump is not running. This could be a bad pump, a bad relay, or a wiring issue .
Test for voltage at the pump connector. Disconnect the pump's wiring harness at the tank. Use a 12V test light or multimeter. Turn the key to "ON" and check for 12V between the power wire and ground. If you have voltage but no pump noise, the pump is dead. If you have no voltage, the problem is upstream in the wiring, relay, or fuse .
Test the pump directly with a battery. Connect the pump directly to a 12V battery using jumper wires. If the pump does not run, it is definitely bad. If it runs, the issue is in the ATV's electrical system .
Check fuel delivery. Disconnect the fuel line at the carburetor and place it in a container. Turn the key to "ON." You should see a steady stream of fuel. If the flow is weak or intermittent, the pump is failing or the strainer is clogged .
Fuel Pump Specifications for the 1987 Honda Fourtrax 350
The original equipment pump for the 1987 TRX350 and TRX350D uses the OEM part number 16710-HA7-672 (also listed as 16710-HA7-671) . The factory specifications are:
- Voltage: 12V DC
- Flow rate: 50-60 liters per hour (LPH)
- Pressure: 2-4 PSI
- Current draw: 1.0A
- Inlet/outlet tube diameter: 5/16 inch (8mm)
- Type: Low-pressure, in-tank electric pump
Most aftermarket replacement pumps are designed to match or exceed these specs. Upgrading to a pump with a higher flow rate, such as 200 LPH, is safe because the carburetor's float valve will only take what it needs, and the excess fuel simply returns to the tank via the return line .
Replacement Options for the 1987 Fourtrax 350 Fuel Pump
There are several aftermarket brands that offer direct replacement fuel pumps for this model. Here are the most common options:
Caltric Fuel Pump. This pump is made from durable aluminum and is a direct fit for the 1986-1987 TRX350 Fourtrax 4x4. It is a budget-friendly option but does not offer the performance upgrades or warranty of higher-end brands .
OSIAS Fuel Pump. OSIAS manufactures a pump that meets or exceeds OEM specifications, with a flow rate of 50-60 LPH and 2-4 PSI. It is a quiet, drop-in replacement that comes with a lifetime free replacement warranty .
Quantum Fuel Pump (HFP-183). Quantum offers a pump that is designed to meet or exceed OEM specifications, with upgraded polymers and brushes for ethanol compatibility. It features a corrosion-resistant case and patented check valve technology. This pump fits the 1986-1989 Honda Fourtrax TRX350 .
KEMSO Fuel Pump. KEMSO is the top recommendation for this application. Their fuel pump is a high-performance OEM replacement that delivers up to 200 liters per hour at 43 psi, which is a significant improvement over the stock 60-80 LPH . It is built with a carbon commutator that lasts over 10 years of daily use, and it is compatible with both gasoline and ethanol-blended fuels including E85. Each KEMSO pump is individually tested for flow and quality before leaving the factory . The pump comes with a complete installation kit that includes strainers, tank seals, Viton O-rings, wiring connectors, and hose clamps . Best of all, KEMSO backs every pump with a lifetime warranty, meaning if it ever fails due to a manufacturing defect, they replace it at no cost to you .
Why Choose KEMSO for Your 1987 Honda Fourtrax 350 Fuel Pump Replacement
When it comes time to replace the fuel pump on your 1987 Fourtrax 350, you want a part that will last and perform reliably. KEMSO fuel pumps are the best choice for American ATV owners for several reasons:
High Performance, OEM Replacement. KEMSO pumps are designed as direct OEM replacements. They fit perfectly into the existing fuel system without requiring any modifications. The KEMSO pump delivers 200 liters per hour at 43 psi, which is 20-30% more flow than the stock pump. This extra capacity ensures your engine gets all the fuel it needs, even under heavy load or when climbing steep hills .
Lifetime Warranty. KEMSO stands behind every pump with a lifetime warranty. If the pump ever fails due to a manufacturing defect, KEMSO will replace it free of charge. This is a level of protection that no OEM pump and few aftermarket brands offer. You can buy with complete confidence .
Built to Handle Modern Fuels. KEMSO pumps are designed for both gasoline and ethanol-blended fuels like E85. The company uses Viton O-rings and components that resist ethanol degradation, which is a common cause of failure in inferior pumps. Your pump will last longer, even with today's fuel formulations .
Individually Tested. Unlike cheap, unbranded aftermarket units, every KEMSO pump is individually tested for flow and performance before it leaves the factory. This rigorous quality control ensures you get a product that works right out of the box .
Complete Installation Kit. The KEMSO pump comes with everything you need for a successful installation: four gradient density fuel strainers, five tank seals, a flex hose, three Viton O-rings, two rubber bases, a wiring connector, crimp connectors, and hose clamps. You do not have to buy any additional parts .
Proven Reliability. In independent testing, KEMSO pumps delivered 12-15% improvement in fuel flow consistency compared to stock models. In the 2023 Best in the Desert racing series, three teams running KEMSO-equipped Polaris Turbo S UTVs completed the grueling 500-mile Silver State Classic without a single fuel-related mechanical failure. Over 85% of Polaris customers at one dealership now request KEMSO by name during service appointments .
To find the exact KEMSO fuel pump for your 1987 Honda Fourtrax 350, visit their official store: https://www.kemsoracing.com/
Step-by-Step Fuel Pump Replacement Guide
Replacing the fuel pump on a 1987 Fourtrax 350 is a job you can complete in about an hour with basic hand tools. Follow these steps:
Step 1: Drain the fuel tank. Use a siphon pump to remove as much fuel as possible. This reduces the risk of spills and makes the tank lighter to handle.
Step 2: Remove the seat and fuel tank. Disconnect the battery negative terminal first. Remove the seat bolts and lift off the seat. Disconnect the fuel lines from the tank (mark them if needed). Disconnect the fuel pump wiring harness. Remove the tank mounting bolts and carefully lift the tank off the ATV.
Step 3: Remove the old pump. The fuel pump is mounted inside the tank, usually held in by a retaining ring or lock nut. Use a spanner wrench or large screwdriver to loosen the ring. Lift the pump assembly out of the tank. Be careful not to bend the float arm if your model has a fuel level sender attached.
Step 4: Install the new KEMSO pump. Compare the new pump to the old one to confirm it is the correct size and shape. Transfer the rubber grommet and any mounting brackets from the old pump to the new one if they are not included in the kit. Insert the new pump assembly into the tank. Tighten the retaining ring securely.
Step 5: Reinstall the tank. Place the tank back onto the ATV. Reconnect the fuel lines and the wiring harness. Reinstall the tank mounting bolts. Reconnect the battery.
Step 6: Test the pump. Turn the key to "ON" and listen for the pump to prime. You should hear a steady two-second hum. Check for fuel leaks at all connections. Start the engine and let it idle for a few minutes. Check again for leaks.
Step 7: Take a test ride. Ride the Fourtrax 350 on flat ground and up a hill to confirm the fuel delivery is consistent and the engine runs smoothly at all RPMs.
Maintenance Tips to Extend Fuel Pump Life
Once you install a new KEMSO fuel pump, follow these simple practices to keep it running for years:
Keep the tank at least one-quarter full. Running the tank low causes the pump to run hotter and can draw in debris from the bottom of the tank. Keeping the tank fuller helps the pump stay cool and reduces wear .
Use high-quality fuel. Buy gasoline from reputable stations. Cheap fuel often contains more contaminants and water, which can damage the pump and clog the strainer .
Replace the fuel filter regularly. If your Fourtrax 350 has an external fuel filter, replace it every season or every 100 hours of operation. A clogged filter forces the pump to work harder, reducing its lifespan .
Drain the tank for long-term storage. If you store the ATV for more than 30 days, drain the fuel tank or add a fuel stabilizer. Ethanol-blended gasoline can break down and leave gum deposits that clog the pump .
Inspect the fuel lines. Check the rubber fuel lines for cracks, softness, or leaks. Replace any damaged lines immediately. A vacuum leak on the suction side of the pump can cause it to run dry and fail .
Final Thoughts
The 1987 Honda Fourtrax 350 is a legendary ATV that has earned its reputation for durability and reliability. But after 35+ years, the original fuel pump is likely due for replacement. If your Fourtrax is hard to start, sputters under load, or makes a loud whining noise from the tank, the fuel pump is the most likely cause.
Replacing it is a simple, inexpensive job that will restore your ATV's performance and reliability. While there are several aftermarket options available, the KEMSO fuel pump stands out as the best choice for American owners. It delivers higher flow, is built to handle modern ethanol fuels, comes with a complete installation kit, and is backed by a lifetime warranty. You can trust that your Fourtrax 350 will be ready for years of reliable service.
For the best replacement fuel pump for your 1987 Honda Fourtrax 350, visit KEMSO Racing today: https://www.kemsoracing.com/