Dirt Bike and Motorcross Forum

Author Topic: Bike won't start - where do you start - hitlist  (Read 751 times)

0 Members and 1 Guest are viewing this topic.


  • Administrator
  • Newbie
  • *****
  • Posts: 7
  • Karma: +0/-0
    • View Profile
Bike won't start - where do you start - hitlist
« on: June 27, 2012, 03:06:43 PM »
A basic couple of steps to check a bike that won't run.

As all small engines the basics are - fuel, spark & air - so work through each step to isolate out the problem.

 1) Air
 Most bikes will run with a fully clogged air filter so air is rarely the problem but it's work just servicing the filter anyhow while you are there.  If foam - I usually rince in fuel then leave to dry and reinstall. Paper cylinder type can be gently be blown out with air gun.

 2) Fuel
 Pull the spark plug out and see if it is wet. If it is dry it will be most likely be a carby related problem. (If wet, try step 3 now) Drain the fuel bowl and try again.  If the spark plug is dry check the fuel tank has fuel. Disconnect the hose from the tank off the carby and make sure fuel is flowing.

If it only runs on choke or when you rev it, it is a blocked pilot jet or water. If it does not rev out it could be a blocked main jet, float problem or the clip of the needle could have come off.

If the bike stops after a couple of minutes it could be your fuel tank cap or breather tube being blocked. Try running with the cap slightly undone (be carefull). This is also a sign of a dying coil or other electrical thing too.

3) Spark
Put the spark plug against the motor with the lead on and kick it over fast. If you don't have spark it is electrical.

Don't worry if the spark seems weak or hard to see, I hear this complaint alot and 99% of the time it is not a problem. Modern ignition color is hard to see. If you are confident it is a problem hold your hand on the plug when kicking it over...WARNING it will hurt if it fires!

 - Change the spark plug and re-test
 - Disconnect the kill switch. Try looping the wires together also as some run open circuit to turn off.
 - Check the coil is earthed properly and the other wires are also attached. Most Jap 4T bikes have the coil built into the lead so you can't do this.
- If you get it running, turn the bars from side to side. If it cuts out check the headlight wires. Disconnect everything and plug it back in, you will be surprised how fury inside some plugs can get.
 - Check battery terminals by wiggling the cables. Tighten them.


Copyright © Monster Forum