Bizarre Electrical Issue

[gman]

Can anyone help with the following please.....

My 2014 EC300 racing (e start) started bogging down in the woods today and giving it a hand full didn't clear it. I changed the plug with no effect so I put it down to crap in the carb. At this point I noticed the digi trip display wasn't lighting and the e start was flat (20 mins earlier it was perfect). I got the bike home, stripped the carb and cleaned it and the air box, put in a clean air filter and started the bike and it still ran rough.

So here's the odd bit...............

I then pulled the plug, shorted it to the engine, cranked the bike using the kickstart and the spark got weaker and weaker until nothing. I waited 5 minutes, and it did the same - strong spark to start until nothing (died after about 5 "cranks"). Next time I waited 20 minutes and cranked the bike over about 20 times this time until the spark went again (it would appear the battery gathered a bit of charge as the digi trip lit up after waiting 20 mins). I checked the battery and its down to 4 volts so it clearly isn't charging but I don't understand why my spark is "fading" - if the kick start is the back up in the event of a flat battery why am I getting a spark only for it to fade until it dies completely?

I know that a duff battery can cause a bike to run rough but any ideas anyone? Battery or something else?

 

[Neil E.]

Your bike has a DC powered CDI, any battery problems will have it doing what you found. The battery is failing or you have a load that is running it down. Check for damaged/pinched wires everywhere. Cut open the loom if it has worm spots. A shorted out wire should be visible due to arcing.

You may have to disconnect every single connector and put it back together one piece at a time while using a multimeter to check for current draw.

A broken wire can have similar results if it stops the CDI from getting power. Charge the battery and hook it up to different bike. See if it can crank the engine without losing cranking speed (a poor man's load test).

 

[gman]

Yep - pretty much thought it was something like this. I couldn't figure out why the kickstart wouldn't start it but if I need the volts for the CDI it makes sense. The auto test on the battery says its low so I've ordered a decent li-pol charger and I'll go from there.

Here's another thought though - i had the engine out and when I put the seat back on everything seemed okay. However, I had to remove the seat and in doing so I could here something shorting and the negative wire was worn and shorted a few times on the frame. Could this have dumped the voltage quickly and could the short have taken something else out?

I started the bike earlier and it was crisp but then bogged and died so it cant be the pick up coil or the magneto coil ????

Give me a mechanical fault any day of the week............

Thanks for your help thus far!

 

[Neil E.]

The negative of the battery is connected to frame ground. There is no way it can short out to the frame. The positive certainly can short out. The most likey scenario is that the seat or something close to the battery has pinched the heavy cables or other wires.

If a wire is crushed enough, strands can break inside the insulation. You have to inspect any wiring near the seat/battery/frame very carefully. I would guess that the battery cables did not slide out of the way and got pinched when you replaced the seat.

The battery can dump a lot of energy quickly if directly shorted. It can overheat and be damaged internally. It may charge up OK but still not function properly under load.

If the short circuit was present while riding, there is a chance some electrical components have been damaged. You may need a dealer's help to track it down further.

 

[gman]

The live was frayed and exposed so if this rubbed then thats where the battery dumped the volts. The battery charged correctly using a li-pol battery charger and its held volts over night so theres no parasitic draw. However, i cranked the engine on the e start and the bendix and crown gear stripped teeth (e start is shocking for eating these parts). I need to get the mag cover off to find the teeth first and then i will start it off the kickstart. I will let you know how it goes.

 

[gman]

Problem found but everyone take note. If you EVER take your magneto cover off check, double check and TRIPLE check that nothing has magnetically attached to it. I took my mag cover off and there was a number 8 hex drive bit right there inside courtesy of my mechanic. Its rubbed the wires on the coil and no doubt trashed it.

I got the bike running courtesy of 45 UK bucks for a battery charger i didn't need....... No ramp up voltage with bike running as it should be about 14 volts across a multi meter so coils isn't charging battery which all now makes sense.

Thanks to Neil for the replies!

 

[(F5)]

OK hard to diagnose that one. Good you found it. Charger will always be useful.