I have a 2003 TW that refuses to start. It was running fine until it suddenly stopped at a stop light. We diagnosed it and found that it had no spark, but after replacing the magneto/stator yesterday we were able to get a visible spark. However, it still isn't starting. It has a new lithium battery we got a little over a month ago. Voltage tests show that its working fine, and we've tried bump starting and jump starting from another battery. We tried starter fluid, and still nothing. Air presses on my finger when holding over the spark plug hole and trying to start it, and it smells of fuel and trips from the carb after the petcock has been left open for a few minutes, so it seems that it has all three elements of spark, fuel, and compression. This bike has had a history of being difficult to start. We're going to go get a compression tester later this after to confirm that we have compression, but after that I'm not sure what to do. Any suggestions would be greatly appreciated!
Could still be a weak ignition coil or weak plug. Could be air filter. Could be fuel quality or supply. Slight chance it's CDI but I think a failing CDI can still start up sometimes. It could be more serious like a messed up valvetrain, cam chain tensioner or very low compression, but those are much less likely to occur at a stoplight unless you were low on oil or had crazy high miles/weird noises and maybe no valve adjustment ever. Just unlikely any of the serious ones like that would happen without warning. What does the spark look like and where did you spray the starter fluid? A better test may be a teaspoon or so of fuel in the spark plug hole. If the fuel was running low it's very possible that something got sucked in and is obstructing fuel delivery. Occasionally folks only find out they were low on fuel when they pull the clutch in or come to a stop and the bike dies. Did it die as you stopped or while stopped?
A. How bright is the spark? Bright white/blue, not yellowish?
B. What is spark plug gap? Under compression, a wide gap may not fire.
C. How new is the spark plug?
D. What is color of spark plug?
E. Has any work been done on the timing chain?
F. What were voltage tests? (1) Key off? (2) Key just turned on? (3)While trying to start?
G. Choke/enrichener on or off?
H. What is setting of mixture screw? Is it open to about 2 1/2 turns from gentle seat?
I. Air filter removed to squirt ether? How much ether? One second blast while cranking?
Last edited by SportsterDoc; 12-27-2018 at 10:07 PM.
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Check all the safety switches. Kill switch, neutral switch, kick stand switch and also all the various ground wires behind the head light, most are black. Any of these switches that fail will cause the bike to not run even if you do see spark at the plug. They are all interconnected into the light box beside the speedometer.
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Since light travels faster than sound, some people appear bright until you hear them speak.If I agreed with you, we'd both be wrong.
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Sounds flooded. Turn the gas OFF and hold the throttle WIDE OPEN and see if it starts. If it does then it is a carb problem.
Long live the internal combustion engine!
This might sound stupid (because it is) but I had pulled the plug on mine to check spark and simply failed to plug the wire in completely when I reinstalled the plug. The spark plug wire "clicked" once and seemed like it was seated but it was not. The spark checked OK when I tested it but obviously the bike wouldn't run when I tried to start it.
I just had to push harder to force a more solid click and it worked fine.