Yamaha AG100 intermittent spark?

[mab165]

Hi all,
HELP!

I am having problems with my mates 2005'ish Yamaha AG100. Was running fine, then starting loosing spark and cutting out. After stopping for a few mins, the spark would magically reappear and bike would run fine, then the same process would repeat. Now it has gotten worse and the intermittent spark cuts in and out more regularly. Note the bike is cold when the spark cuts in or out.

I also have a 1980 Yamaha Ag100 which is a sweet runner and have been swapping the eletrical components one by one with the broken AG to see if I can isolate the cause. I have checked the Sparkplug, Blackbox Ignition timing thingy, ignition coil and spark plug leads. Thought I had isolated the cause to the stator/pickup coil, so bought a 2nd hand one, changed a few of the wires to make it match the wire outputs (coil had four wires coming out instead of the 3 on my one). The bike fired up, then the intermittent spark came back again. I am now pissed off and dont know what to check next. I note that the bike has an old battery in it, but it is 10yrs old and shot. I didnt think the battery would be necessary to run the bike so have ignored it. Is this assumption correct?

My last resort is to cut open the wiring loom and trace all the main wires through to check they are not broken. Does anyone have any suggestions for things I can check which I havent thought of before I do this? I have a multimeter and am fairly handy with it, but need concise instructions to know what to look for. Thanks for your assistance!

[cave weta]

Just let the poor thing go...... It has served well and is in no mood to carry on. just push it to the back of the shed and Buy another bike.....

You can chase this stuff for hours and get nowhere. at $65.00 per hour you are pushing good money after bad with an electrician.

move on

[ducatilover]

Are you sure it's losing spark?

Bridge all the wires from the pick up to the CDI, then to the coil. If it works happily, you have a problem in the loom, if it still shags out, clean all the earths, double check the coil mount and coil are okay.

When it cuts out, check continuity over the ignition and kill switch circuits.

Basically try find where the voltage is running away from...

[FJRider]

i note that the bike has an old battery in it, but it is 10yrs old and shot. I didnt think the battery would be necessary to run the bike so have ignored it. Is this assumption correct?

no ... !!!!!!!!

[gammaguy]

broken wire somewhere probably near the steering head

good luck

[mab165]

Thanks for the reponses guys. I've stripped back the wiring loom and have been checking all of the wires for breaks. Nothing obvious at this stage.Still looking....still hoping.....

[mab165]

Hi there. What do you mean bridging all the wires together?

[ducatilover]

Hi there. What do you mean bridging all the wires together?

Just run an extra wire next to the originals, one at a time.
Or just go check continuity

[mab165]

Well. I've now tried everything including checking for continuity/bridging along the loom. Couldnt find anything wrong. As a last resort I cleaned and wire brushed out the connecting plugs. Now I am getting consistent spark, but it looks a very weak blue colour and is not strong enough to fire up the engine. Any suggestions?

Note I have a replacement Stator/pick up coil installed, which had four wires protuding, whereas the original stator/pickup oil on the bike had only 3 wires protuding. I am thinking maybe I should link one of the wires togther to give the equivalent 3 wires instead of just leaving one of the wires hanging and unconnected?

[karmobRob]

I bet the stator is the problem, can you put up pics of both stators. The extra wire may be an external earth.

[Cammey]

I can't quite tell from your description, if you have swapped the coil out. Its quite common for a coil to work for a few minutes, then break down internally as it get warms. It will often then work again once cool.

I'm not familiar with the electrical design of the AG100, but I worked as an auto electrician, and coil failure like this (or lead - plug cap) were common on cars.

I also would comment that any testing on a vehicle with a known faulty battery is a problem looking for a technician to exploit !

[mab165]

I bet the stator is the problem, can you put up pics of both stators. The extra wire may be an external earth.

I'm not sure about the configuration of the stators, but if you look at the photos, you will notice their is an extra wire in the replacement (new) stator, when compared to the original stator. Help.