Has your bike got a contactbreaker ignition or a CDI ignition?
If you've got a contactbreaker ignition:
- Disconnect the battery
- Disconnect the black wire coming from the ignition (ignition is located underneath the flywheel)
- Make sure the lights are turned off or you're going to blow out the bulbs
- Take off the flywheel cover so you can see the flywheel and see the contactbreakers through the openings in the flywheel
- Krank the engine and look at the contactbreakers
- If the contactbreakers are giving sparks the ignition is fine, if not you've found the problem --> Replace the ignition condensor and maybe the ignition coil (could be burnt out).
- Replace the flywheel cover, reconnect the black wire and the battery
From here on it goes for CDI ignition as well:
- Screw out the sparkplug and remove the sparkplugcap from the ignition cable
- Turn a screw or push a nail into the sparkplugwire and hold it near the cylinderhead while kranking the engine
- If there's a spark the ignition cable and the bobine (high-voltage ignition coil) are fine. If not you should first check the bobine grounding (poor grounding will result in no spark). If that isn't it replace the ignition cable (only a few dollars) and try again, if it still doesn't give a spark the bobine is wasted and should be replaced.
- Replace the sparkplugcap and turn a screw into the cap and check if it will spark against the cylinderhead, if there's no spark the sparkplugcap is wasted and should be replaced.
- Now try it with the sparkplug in the cap and replace it for a new one if the plug won't spark.
If you've got a contactbreaker ignition and the problem still isn't fixed you should run through the list again because you've now checked the entire ignition system, the problem's in there somewhere.
If you've got a CDI ignition and it just won't spark the problem is in the bobine, the CDI unit, the ignition coil underneath the flywheel or the ignition-timing sensor next to the flywheel.
- You should first measure the electronic resistance of the ignition coil underneath the flywheel, if the resistance is high the coil is wasted. You can check the resistance by connecting a lightbulb and a battery onto the coil, if the light wont light up the resistance is high and so the coil is wasted.
- Reconnect everything you disconnected and connect a lightbulb onto the blue/yellow wire coming from the ignition timing sensor next to the flywheel. On Honda CDI ignition the timing wire is always blue with a yellow stripe. If the bulb doesn't light up when you krank the engine the timing sensor is the problem and should be replaced.
- Reconnect everything and krank again. If there still is no spark there's only one thing left that could be the problem: the CDI unit. The CDI unit is that little black (sometimes blue) box-thing with those 5 or 6 wires coming out of it. CDI untis vary a lot in price, the cheapest is only a few dollars while the highly tuned racing CDI units cost hundreds of dollars.