Bike won't start! help please :(

[MRFINCH]

Tried starting my 1980 XS400 yesterday after it had sat for a few weeks and it just wouldn't fire up. plenty of power turning it over and spark plugs are wet so its getting fuel. Could it be an electrical problem? what are the first things to test? Thanks, Sam

 

[rugbywarrior89]

Make sure you are getting spark. If you have gas, there should be ignition. Of course, the plugs being wet isn't a good thing. That would indicate that you are flooded. That could also be why it doesn't start.

 

[Sesty]

Wont hurt to check your compression also

 

[MRFINCH]

nope, no spark. What could be the causes for that?

 

[MRFINCH]

Forgot to say it is an electronic ignition model

 

[Scorpio1963]

Worst case sceanario your igniter box has failed,check the ignition fuse and make sure its good.Could also be coils but I doubt both would fail at the same time.Get a new set of plugs and try that.

 

[MRFINCH]

All fuses are in order. I thought it could be coils but you're right, that would be odd. Plugs are about 2 months old but have barely done any work as the bike has only been round a car park, they are a bit sooty but should be fine! Guess that narrows it down to the CDI unit? :/

 

[MRFINCH]

Is there ant way to test the CDI unit?

 

[Sesty]

i dont think is a away to check the TCI box. You can test the components that are wired to the TCI and if they are A-OK then the box must be fried....

or can swap one in from a parts bike or off ebay. Some members have had success re-soldering the connections but might just be easier to swap in another one.

 

[xschris]

If the plugs are wet and sooty replace them so you can rule that out. If the new plugs have no spark start checking connections.

 

[Scorpio1963]

Theres not realy a way to test the cdi unit but you can take it out of its housing and see what it looks like.It could be clean and still at fault or could be all corroded and be at fault.
Also don't rule out the relays those little brass boxes on the right hand side of the bike.

 

[arfstrom]

It is more common that the wires just fail. do a Coil check, then nip off a half inch on each side of the each plug wire. So simple, but people will fail to do it to both ends. One person did not consider to pull it off the coil, so don't be that person. (apparently I didn't spell check it right.)

 

[MRFINCH]

Surely if a cable fails it would only be one side not getting a spark? and it would be a weird coincidence if they both went at the same time. Ordered a know to be working CDI unit so should get that next week.

 

[XS400NJ]

I would trace problem in this sequence:
- is there high voltage impulse to the plug. (I would use a plug that I know is working and look for spark, or would use my finger as final test).
- is there low voltage impulse to the coil (digital voltmeter should do).
- is there low voltage impulse out of the ignition box.
- is there power coming to ignition box.
- is there timing signal coming to ignition box.

Few weeks of sitting rarely would kill ignition box, but it would often collect some water condensation in the tank, or would make some electrical contacts bad. Simply connecting/disconnecting all related wires may fix the problem.

just my 2 cents...

 

[arfstrom]

I had an occasion last year, where like you reported, no start situation, I massage the cable ends, tighten them and try it again, that worked. not all problems will be fixed with a simple playing with the wires, but it does happen. (it is a cheap, fast and easy test/process)

I suspect that if you leave your bike to the elements, (park outside) that the overnight temp variate, just enough to temp the electrical gremlins. perhaps a multi-day leaving alone. Then its just mad at you. Look at Scorpio's situation, The bike had no love all winter, and now his bike has been sulking all summer. (I am in the same boat with you Scorpy)

 

[MRFINCH]

Sorry, keep forgetting to update you guys. CDI unit made no change so replaced plugs, leads and connectors and its running better than ever. I think it was the combo of 34 year old parts and being left. Cheers for the help.

 

[xschris]

Good to hear