ATV Troubleshooting Guide

Date:May 25, 2020

Engine turns over but does not start

No Fuel

Dirt in fuel line or fuel filter

Fuel will not pass through on-off valve (petcock)

Fuel tank vent plugged

Carburetor starter circuit

Engine flooded

Low compression

No spark





Add fuel as required

Clean or replace valve as necessary

Repair vent system

Clean or replace as needed

Turn off fuel and drain crankcase
A) Inspect carburator venting system for blockage
B) Inspect carburator needle and seat
C) Inpect head gasket
D) Inspect piston and cylinder, repair as required

Check for proper spark plug connection


Engine does not turn over



Dead Battery

Starter motor does not turn

Engine stuck or froze


Change or replace battery

Repair or replace starter motor

Repair engine as required


Engine runs but will not idle


Plugged carburetor pilot system

Carburetor improperly adjusted

Low compression

Crankcase leak






Clean or replace pilot jet<

Adjust carburetor per specifications

Adjust choke per specifications

Repair engine as required

Repair or replace crankcase as required



Engine runs but will not rev up


Broken throttle cable

Obstructed air intake

Incorrect carburetor jetting

Incorrect ignition timing

Restricted exhaust system





Replace throttle cable

Clean or repair air intake, replace air filter

Jet as per jetting chart for carburetor

Check and adjust ignition timing

Repair, clean or replace exhaust system


Engine has low power


Cylinder, piston and ring wear or damaged

PVT not working properly

Restricted or blocked exhaust


Perform compression check

Clean, repair or replace as needed

Repair, clean or replace exhaust system


Piston scoring


Lack of lubrication

Fill oil tank and bleed oil pump

Check oil pump for proper operation or restricted vent line

Restricted oil delivery

Oil pump drive gear failure

Melted Piston top


Engine overheating

Lean air fuel ration

Air leak in crankcase

Incorrect ignition timing

Incorrect spark plug





Low coolent level in radiator (liquid cooled)

Restricted cooling fins (air cooled)

Clean carburetor and jets

Repair as needed

Adjust timing per specification

Install correct spark plug


Broken piston skirt


Piston fatigue from scoring

Excessive piston to cylinder clearance


Repair or replace cylinder and piston



Excessive smoke and carbon build up


Oil pump not adjusted properly

Oil pump cable not allowing pump to return to idle position

Synchronize pump to carburetor

Lubricate or replace cable

Engine coolent found in counter balance assembly


Water pump gasket

Water pump seals


Replace water pump gasket

Replace water pump seals


Blown engine


Skirt broken off piston, hole in crankcase

Bearings on counter balance shaft failed

Engine stuck or froze


Both result in engine not running, full compression. No crankcase pressure, which is needed for 2 stroke engine

Replace crankcase and other related parts.