ignition system current starvation

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Wed 8 Feb 2006 15:25
ignition system current starvation - circlip
I have a single cylinder four stroke motorscooter that has a weak spark resulting in poor/non starting. When it does start, it runs well. I have narrowed it down to a weak spark, which is orangey yellow in appearence. The bike has no kick start lever and cannot be bump started because it is automatic. It has electronic ignition ie. no contact breakers and I have checked everything else, like the coil, plug, HT lead, earths, etc etc but NOT the battery. The bike cranks well and all the lights are also ok. However, the pathetic spark will not ignite the fuel air mixture and it floods. The carb' has been stripped, inspected and cleaned and it not at fault. I have heard of a condition called 'current starvation' which I think means that the battery can crank the starter motor, but has not got enough power to concurrently provide sufficient current to the ignition system to produce a strong blue spark. Has anyone heard of this? The battery is now 5 years old and done 18000 miles on the bike.
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Wed 8 Feb 2006 15:54
ignition system current starvation - bikemade3
Duff battery, possible plate sulphation limiting its ability to supply amps, hence why, when it's running it runs fine.
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Wed 8 Feb 2006 15:56
ignition system current starvation - Peter D
5 years for a bike battery with electric start is a long time. Jump the battery with another one ( On loan or waht ever ) and try starting it, if it's ok then your battery is on the way out. The other possibility could be a shorted turn in the coil, this will give you similair results as you have described. Regards Peter
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Tue 14 Feb 2006 00:45
ignition system current starvation - circlip
As a result, I have now replaced the battery and all is well. After cleaning the spark plug the bike coughed into life, cleared its throat and off it went, running like dream. What threw me, was that the battery would crank the bike over well and power the lights. I assumed (Doh!) that the battery was therefore fine and looked elsewhere for the problem. Whenever I've had a duff battery before on any vehicle, the first indication of it failing was slow cranking and poor starting - well you live and learn!
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