How to Change a Cracked Fuel Line on the 2017 Kymco MXU 700i

Shop parts for a 2017 Kymco MXU 700i ATV.

Fuel hose is one of the few parts on a machine that ages out whether you use it or not. Riding it hard wears it; letting it sit wears it differently. Either way, the rubber on a 2017 MXU 700i eventually hardens, cracks, and needs replacing. The job is well within the reach of an intermediate home mechanic, with one important caveat: this quad is fuel injected, so the line is pressurized by a pump inside the tank and has to be bled before you open anything.

The Two Ways a Fuel Line Dies

Externally, it is a story of lost flexibility. The compounds blended into fuel hose to keep it soft gradually migrate out and evaporate, leaving a wall that is hard and prone to splitting. Heat radiating off the 695cc single accelerates the process, and once the hose has stiffened, ordinary vibration and chassis flex begin checking the surface into fine cracks. Owners in dry, hot regions notice this sooner, since low ambient humidity pulls residual moisture out of the rubber and hardens it from the outside inward.

Internally, it is chemistry. Ethanol-blended gasoline draws water vapor out of the air, and the resulting mixture attacks the inner liner, which softens, swells, and starts shedding fine particles downstream toward the injector. Fuel that sits in the system through months of non-use deposits gum and varnish on top of that damage, restricting flow and gluing the hose to its fittings. The result is a line that may look fine from a few feet away and be finished where it matters.

Assembling What You Need

  • Rubber or nitrile gloves along with eye protection
  • An approved container for the fuel you capture during the job
  • Replacement hose rated for fuel-injection pressure in the original inside diameter, not general-purpose carburetor hose
  • Fresh clamps matched to your fitting style, plus a quick-connect release tool if your machine uses a locking coupler
  • Line-clamping pliers, since an injected machine has no petcock to close
  • Socket set, screwdrivers, pliers, a razor knife, and plenty of rags

On safety, one point genuinely matters. Gasoline vapor is heavier than air, which means it drops to the floor and travels along the ground toward whatever might ignite it. Ventilation at ground level is therefore what protects you, not an open window overhead. Open the garage door completely and put a fan on the floor moving air outward, or do the work outside. Shut off appliances with standing pilot flames, keep the battery disconnected once the system is open, keep hot work lamps and chargers away from the area, and spread fuel-damp rags outdoors to dry rather than sealing them in a container.

Symptoms Before Failure

  • A fuel smell near the tank that is strongest right after shutdown, while the circuit is still pressurized
  • A wet patch or small puddle beneath the machine, though pressurized fuel commonly evaporates before it drips
  • Cracking, a chalky feel, or a rigid section that keeps a crease when pinched
  • A ring of fuel-stained dust at either fitting, the telltale of slow weeping
  • Bogging under load, hesitation on hard acceleration, or a lean condition as revs climb

Pinch the hose along its full length as part of the inspection. Sound rubber compresses and rebounds; a hose that has hardened feels rigid, or it holds the shape you press into it. Because a small pressure-side leak often leaves no visible trace, the odor is frequently the only early clue you get.

Bleeding Pressure and Removing the Hose

Start by pulling the fuel pump fuse or relay, then crank the engine until it stalls to burn off the stored pressure. Switch the key off and disconnect the battery negative cable so the pump cannot run with a fitting open. Take the seat off along with enough bodywork to see the tank connection and the run to the throttle body at once, and photograph the routing and clips before anything moves.

Slide a drain pan underneath and lay a rag over each fitting as you open it, because residual fuel stays in the line even after bleeding. Clamped ends need the clamp walked well back along the hose first. A self-locking quick-connect needs its tabs pressed squarely and the coupler pulled straight off, never levered sideways, because aged plastic collars crack under that kind of load. Clamping pliers isolate any low-pressure section that would otherwise drain out.

Twist the old hose gently to break the varnish bond at the barb instead of pulling hard on it, and when a section refuses to release, slit it lengthwise with the razor and peel it away. As you free the line, note the clearance points it negotiates. This is a four-wheel-drive chassis, so the hose crosses front differential hardware and extra frame crossmembers that a two-wheel-drive machine does not have.

Installing the Replacement

Use the old hose as your template and cut the new one to match. Excess length sags toward the front driveline or abrades against a frame tube, while a piece cut short keeps tension on both fittings every time the engine shifts on its mounts. Push each end on dry until it bottoms fully past the raised bead on the barb.

Leave the grease and the silicone spray on the shelf. Any lubricant on a fitting gives pressurized fuel a channel to creep out from under the hose, and no amount of clamp torque will seal it back up. If the new hose resists going on, hold the end in hot water briefly and it will slide into place. Set each clamp just behind the bead and tighten evenly until the hose no longer rotates by hand, stopping before the band cuts into the wall. Where the tank end uses a self-locking quick-connect, push until you hear the collar click and then pull firmly to confirm it latched, adding no clamp there. Route the line back through its original clips, clear of exhaust heat, the front driveline, and suspension travel.

Pressure Test and Final Checks

Reinstall the fuel pump fuse, Reconnect the battery, and cycle the key on and off several times without cranking the engine. Each cycle runs the pump and brings the line up to pressure, which is when a joint that is not quite right will show itself while the area is still clean and dry. Run a finger around both connections and watch for beading or a fresh spot on a rag laid underneath.

Once both joints stay dry, start the engine and inspect again while it idles and vibrates, then blip the throttle a few times and check once more. Give it several minutes of leak-free running, take a short lap, and look one final time before the plastics go back on for good. Worth keeping in mind on this machine: the fuel filter is built into the in-tank pump assembly rather than sitting inline where you can service it, so if the 700i still acts starved under load after a clean installation, the in-tank unit is your next stop.

Related Shopping Categories

Shop Fuel Lines for a 2017 Kymco MXU 700i ATV.

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Shop Petcocks for a 2017 Kymco MXU 700i ATV.

Shop Fuel Filters for a 2017 Kymco MXU 700i ATV.

Shop Fuel Stabilizer for a 2017 Kymco MXU 700i ATV.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your ATV's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.