GT380A no spark

[gingerchunkyboy]

First of all can I say hello to everybody . My name is Paul and I live in Aylesbury UK . I have a GT380A 1976 I am the second owner from new and I have owned the bike for about 10 years . She was fully restored by my self in 2011 and she has been no bother until now, my problem is that that she has no spark at all when I kick her over so I replaced the battery and she fired up fine but after ticking over for a little while she stopped sparking. I charged the battery overnight and she fired up again ,so I took some measurements at the battery at tick over she was producing 12 volts and at 5000rpm she was producing 15.5 volts . I then took her for a 50 mile ride and she behaved perfectly until 1 mile from home when she stopped sparking again. She has a factory points system fitted all standard when she does spark all 3 contacts and plugs give a good bright spark. If any body has experienced this before I would be grateful for any suggestion's before I load the parts cannon and spend lots off money chasing this problem . thanks Paul

[Zunspec4]

Hi gcb,

15.5 volts at 5000 will result in overcharging. It is ideally in the 13 - 13.5 volt range. Not sure how that is affecting your ignition though. When at 15.5 volts coils also see this voltage not just the battery. It could be the high voltage is causing the coils to draw a higher current (which equals heat) and you are getting a breakdown in the coil windings as a result.

Cheers Geoff

[Alan H]

Sounds like a charging issue and your battery is going flat. Suzy triples like a nice healthy battery or they won't run right.
Just a thought, what battery have you got on and how old is it?
Is the acid level OK in all the cells?
15.5v is too high and if your battery really is OK, it will cause overheating issues in the electrics at the very least.
Another favourite is bad/poor connections and poor earths.
Pull everything apart (1 at a time!) and clean/contact lube connections.