ATV Sat For 5 Years (Don’t ignore this advice)

Finding and fixing up an old ATV is an exciting journey. I’ve rescued a ton over the years, buying barn finds, fixing, and flipping.

An ATV engine that sits for years may have stuck rings or valves. Attempting to start it without first checking engine condition could cause severe damage. Lubing the cylinder and cranking over it by hand will minimize the risk of damage. Other components that will require attention include:

  • Battery and terminals
  • Fuel system
  • Ignition system
  • Oil and filter change

In this post, you’ll learn what you should never do to an ATV engine that’s been sitting for years. You’ll also learn about the components that will need attention, how to test them and how to fix them. By the end of this post, you’ll know exactly what you need to do to get it humming.

Atv piston

Avoid Major Engine Damage

An engine the sits idle attracts moisture, even on the inside. Moisture given the opportunity turns to corrosion, and that can cause components to stick.

Engine piston rings and valves are components that are susceptible to sticking. Attempting to crank over the engine without following the proper procedure risks breaking the rings and bending valves. Both repairs require lots of dollars and a major strip down.

Juicing her up and trying to start her right away is understandable. You are excited to make progress. But when it comes to standing engines, we’ll need to exercise some patience.

The best approach is to begin by removing the spark plug and using a suitable funnel 1/2 fill the cylinder with a mix of diesel and paraffin.

Leave the mix to sit overnight. It will penetrate and lubricate the cylinder and release the rings if stuck.

The following day, remove the flywheel plug and, using a socket and ratchet, turn over the engine gently clockwise by hand. If you feel any resistance, stop turning, remove the valve covers, and inspect for sticking valves.

A sticking valve usually needs nothing more than a gentle tap to release.


The battery will be flat, and due to sulfation will also be beyond repair, a new battery will be needed. Your battery terminals will also need to be cleaned using grit paper. A coating of petroleum Jelly or dielectric grease after installation will prevent corrosion.

When running, the battery charging system will need to be checked. A failed rectifier/regulator is common.

Fuel System

The fuel system will consume the bulk of your attention. It would need a lot of love unless the bike was stored dry, which isn’t usual. Old gas turns to a gummy, sticky deposit and will corrode internal carburetor components.

Most ATVs will use a mechanical or vacuum slide carburetor. You’ll need to remove the carburetor and thoroughly clean it in an ultrasonic tank.

While stripped, you’ll need to inspect the pilot jet, main jet, needle jet, emulsion tube, float, needle and seat, mix screw. The slide, mechanical, or vacuum may need attention too.

Most ATVs use an acell pump to inject a shot of gas into the carburetor when the throttle is nailed from idle. The pump diaphragm will need to be replaced, and the carburetor leak jet will be tested.

It’s also very possible that the carburetor is faulty. Old gas can cause a lot of internal damage. Sometimes a replacement is a better bet.

Other fuel system components like gas tanks need to be cleaned, fuel lines, clamps, and vacuum hoses checked and replaced if necessary.

Petcock checked and replaced if it’s vacuum-operated, and the fuel filter changed.

Ignition System

A new spark plug, check the cap and plug wire for rodent damage. Ignition systems on a barn find usually fail after the engine starts and runs a while, so don’t be surprised if you’re diagnosing a no spark at a later time.

A faulty start relay and a faulty solenoid are common. A click noise that resembles a flat battery is the sound of a failed starter solenoid. A failed starter is possible too, but most times, it’s just the solenoid.

Oil & Filter

Before you attempt to start the engine, go ahead and drop the oil and filter, the engine will hold a lot of moisture. After the engine’s been running and warm, the oil and filter should be changed again.

Coolant System

The coolant system will need to be flushed, replace the thermostat, rad cap, check hoses – replaced if damaged. Add new coolant, and the system will need to be bled, checked for leaks, and cooling fan operation checked.


The brake drums or rotors will likely be corroded and may be seized. Removing, cleaning, and replacing pads/shoes should solve that problem.

Brake fluid absorbs moisture, and that can cause problems inside a brake system, don’t be surprised if brake calipers are sticking and wheel cylinders are leaking.

Brake flexi hoses may also perish.

Transmission & Axles

Depending on what type of transmission you have, you’ll need to change oil and check belts.

You may find these posts useful:

Start a flooded bike

Bike start with faulty stator?

Why is my bike bogging down?

Bike dies when I give it gas

Will dirt bike start without an air filter?

John Cunningham

John Cunningham is a certified mechanic and writer on I’ve been a mechanic for over twenty-five years, I use my knowledge and experience to write articles that help fellow gear-heads with all aspects of ATV ownership, from maintenance & repair to troubleshooting.

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