Blue spark from contact breaker

[erik_w]

Hello!

I am working on an older two cylinder, two stroke bike and I am having some trouble with the contact breakers. During operation there is a very clear blue / White spark coming from one of the breakers, it increases in intensity as you rev the Engine. The Engine is also tricky to start, especially when hot, and it seems like it doesn't quite right in general.

My question is what might be causing this?

Knowing that this is a Classic sympthom of a failing condeser, I switched it for a new one, but that didn't solve the problem! Either the new condenser (mF unknown) is too weak or it is also bad.

But assuming that the condenser is fine, can there be something else that is causing this?

Here is a youtube video of the sparks: https://www.youtube.com/watch?v=SNFM2XxIulc

Thanks guys!

[crc]

I would've thought it was the condenser. maybe try yet another one? new doesn't always mean its not faulty

[erik_w]

It is a two breakers, two condenser setup. Can Points not being flush cause this type of arcing as well?

Erik

[erik_w]

Thanks, I'll try to switch the condensers and see what happens. The other one is arcing as well, but not as much - so I don't have much hope :)

I have now ordered "Made in Germany" condensers - might as well do it right!

Somebody said this could be caused by insufficient resistance between the coil and Points - what do you say about that?

[rodekyll]

If the points are pitted or misaligned they might do that with a good condenser.  Also, if the set side of the points is not getting a good ground due to dirt or oil on the points plate or because the dizzy isn't grounding well it will arc as it tries to overcome the resistance.

One way to tell a bad condenser, given the arc, is to decide which direction the arc is going -- from the floating side -> anchored or v/v.  If it's coming from the anchored side it's a condenser.  To see it, put a thin bit of thin paper between the points and watch as they open and close (you ought to be able to fire them by hand).  You should be able to see which side of the paper the arc occurs on.  If you can't see, pull the paper and check it.  The arcing side will have a 'powder burn'.  Another way is to check the pits and fangs.  The points will grow a fang on the arcing side and a pit on the receiving side.  Again, an arc from the set point to the floating point indicates that the condenser isn't able to collect and drain the current.

With an engine scope you can see that the condenser attenuates the current surges going through the points.  That keeps the current from reflecting back up from ground.  (this might not be entirely accurate, but you get the point)  The condenser collects that current and drains it to ground in an orderly fashion.  If the condenser is bad, the reflected current makes an arc from the set point to the floating point.

[Rough Edge racing]

 One time I got several faulty condensers... I have tested many condensers from different vehicles and bikes on a capacitance meter. The good ones all measured between .20 and .27 micro farads. So you might say any condensers of similar size will do the job.

[Wayne Orwig]

Check the secondary wiring to the spark plug. If the wire is bad, or even the spark plug is bad, that extra energy has to go somewhere, and it can end up being arcing at the points.

[Triple Jim]

TJ , where are you ?

I'm here watching.   All the responses are good, and I didn't have anything to add.  It sounds like a bad condenser, but of course it could be something unusual as well.  If it's really not the condenser, maybe check the coil or swap it with a known good one.

[pressureangle]

Video says it's private, can't view it.

Is it a magneto ignition or battery? If battery, is it 6 or 12 volt? The point being to know that you have the correct voltage battery, 12 volts works great in a 6 volt system but kills the ignition components pretty quickly.

[erik_w]

thanks for all the great replies! I will check the points for alignment and use the paper trick. if the are pitted, does that mean they are junk or can I recondition them somehow?

it's a 12 volt system and all components, bar battery and plugs, are original. I've also checked the sparkplug leads using a meter.

I've fixed the video so it's public now.

[rodekyll]

Use a points file and dress them.  The pits don't matter as much as the fangs.

[Gearhead]

When I used to work on import cars, one time a guy brought in a MGB that was running really bad and arcing at the points.  Turns out he switched the wires on the coil, reversing the polarity.  Shows on the oscilloscope as an upside down wave form!  Kind of a long shot, but worth double checking.

Pete

[LaMojo]

If the system has two separate ignition coils, the coil that the points are firing is probably faulty - sparking internally back to the primary winding.
 

[dilligaf]

Use a points file and dress them.  The pits don't matter as much as the fangs.

 :+1 Also spray some electrical cleaner between the points.  Then when the points are closed pry them open and insert a business card.  Move the card back and forth then pry the points open and remove the card.  DO NOT JUST PULL THE CARD OUT.  :BEER:
Matt

[erik_w]

I've ordered new points and condensers, I'll install them to start out with, if the problem persists I'll swap the coils to see if that makes the arcing switch point - thanks guys!