Four stroke engine troubleshoot

Motorcycle engine






Engine will not start



ENGINE STARTS


Engine will start

>> >>
v





Engine will not start




Engine Runs Poorly



Inspect oil
Warped cylinder
Broken ring
Loose part
obstructing <topend
Bottom end
     v
<SEIZED

(Kickstart will not turn engine)
No Start
Not Seized
>
Check fuel delivery system >
Loosen carburetor drain valve >
No Fuel >
Fuel Present
v
v
v
v
v
v
Tank valve
Fuel line

Cap vent
Seat valve
Vacuum hose
Trash in carburetor

<






>
v
       v
      High <   Speed
      v
     
v
     
v
 v
        v


Check crankcase

Check for spark  v < <                        < <         <

       v

Exhaust
< High Compression
Valve clearence
Timing

   v
Dry Plug
<
Wet
Plug
 v
<Spark Present

No Spark>
Ignition coil
CDI
Magneto
Switch
Check spark


 Air
 

<
Magneto Pickup
<


>
<


>
<


>
    <  v

Low Speed
>


Check
Intake gaskets
Bowl screws
Vacuum
line
Ignition switch

     v

    v  >>        >> ^   > Seat valve
Plug gap




AIR Cut-off
diaphram
spring
Blocked passage

    v >> >> >> v EXCESSIVE NOISE
   v








      >> >> HEAD
Incorrect valve setting (gap) > Adjust valves> Check adjusting screw for wear








Worn cam> Replace cam









Worn rockerarm> Replace rockerarm








CYLINDER
Cylinder wall worn










Piston worn










Piston rings worn, weak, broken







110cc Top End Diagram

GY6 50cc Engine Diagram





Piston pin, connecting rod, worn










Cam chain tension lever worn










Cam sprocket worn








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