Yamaha Neos 50 2004 elecrical problems.

I've been struggling with a most unusual problem for the past couple of weeks. The Neos has been laid up for a few months while I've been working on my Vespa ET4, but the time came to get it back on the road and running again. I turned the key and..... nothing! OK, flat battery, get in on charge. Still nothing, and nothing even with a new battery. Got the booster box on it and eventually got some power and the starter would go, but only sometimes. In desperation I kicked the starter and it got going immediately, with EVERYTHING working perfectly, lights, indicators, horn, the works. The current situation is that turning the key does nothing, no dash lights or starter, but kick it and it goes fine.
I've had a good look around, cleaned up a load of connectors, checked switches, cleaned up the earth on the starter and coil, and it's made not a bit of difference.
Any suggestions gratefully received!

 

Sorry to sound so basic, but battery sounds most likely the issue.
Easy test, charge it fully and try and start your vespa with it. And if you can, try your vespa battery on your neos. And of course I'm sure you have done, check the main fuse.

Furthermore, check for bad, loose or dirty connections from the battery to the starter and to earth.

 

Done all that and more! I have a Booster box that will start a Campervan 3.2 TDi engine, but no joy at present. Do you know where all the earth points are on a Neos?

 

I have a 2002 Neos and it has a starter relay, maybe that ?
Mine is under the battery cover a few inches back from the battery clipped to the frame in a rubber holder
if the starter is not working can you hear a click from it?
A standard car relay will do the check circuit to see if the starter will work
If you have a side stand most have a switch on them that cuts the power to the starter, this stand has to be up

 

Hi guys,

I have recently purchased an sinnis phoenix 50cc as no spark to sort it out and keep it...so far i have changed the stator , and ignition coil and spark plug, i have tested on my friend scooter the cdi and also the started selenoid coil and still no spark ....any ideas ? Thanks

 

The starter relay is OK, I've checked that it works when energised, and completes the circuit which should operate the starter, but the problem is there's no supply to the coil. When I turn the key there's no power to ANYTHING, so pressing the starter switch has no effect. Once again, when I kick start, it runs perfectly and EVERYTHING powers up. I'm beginning to think it's the ignition switch. Is there a way to bypass this to see if that's where the fault lies? I'll let you all know if I find a solution!

 

Halle-flippin'-lujeah! Having ruled out every other possible issue I've found that there is no reliable feed from battery, through the fuse, to the starter switch. I can only assume there's a broken wire in the loom heading up the the switch. I've just run a wire directly from the fuse to the ignition swiths and everything now works perfectly. So it's an invisible broken wire, which explains why I've failed to track it down until now. I managed to download a decent wiring diagram from this link https://manualzz.com/doc/922869/yamaha-neo-s-yn50-service-manual and this has been invaluable in figuring out the problem.

 

Starter solenoid has nothing to do with the spark. Have you actually checked if the plug is sparking or not? Unscrew the plug, leave the lead attached, place the metal side of the plug against a metal part of the engine and crank the starter. You should be able to see it sparking. If it is and you still can't get the bike to start is there fuel getting through? Plug back in, crank it on the starter then pull out the plug and see if it smells of petrol or not. If you have fuel and spark, then there must be a problem with the ignition timing. You need a systematic approach. Assuming, as you say, that there's no spark, and you have a new stator, coil and plug, and a working CDI unit, the ONLY other thing that can be wrong is the wiring from stator to CDI and from CDI to coil. Try running new wires and see if you can get a spark. One final thought - does the Phoenix have an Immobiliser?