zapping sound coming from under my stator cover

[bigskybldr]

After parking my bike('77 gs 750) it will start making a zappng noise, It will make one zap about every 5 or 10 minutes. After a few hours it will stop doing it. The charging system works great, the battery is always at a full charge when I check it. Is this a sign my stator is heading south?

 

[Agemax]

are you sure it isn't the engine fins "pinging" as the motor cools down? most air cooled engines do it, especially the old GS's. have you still got the rubber dampers that slot inbetween the cooling fins on the block? these are fitted to prevent this pinging sound

 

[bigskybldr]

The dampers are still in place and the exhaust and engine make the usual sounds of a hot engine cooling down. This is a fairly loud zap, it definitely gets your attention when it goes off. A few times I've heard it still doing it the next morning. At first I had a hard time tracking the noise down so I sat and waited on both sides of the bike till I located where it was coming from. It's kind of like the arcing sound a bug makes when it flies into one of those electric bug zappers.

 

[Agemax]

hmmmm, never heard this one before. next time you park up, disconnect the battery completely and see if it still does it.
if it does then you have a naughty electrical pixie causing trouble somewhere!

 

[Guest]

They tend to do that regardless of the fin blocks as they cool down. A loud snapping sound, sometimes long after you would have thought it was cool. There us nothing in the stator that could cause an arcing sound unless the motor was spinning and then you couldn't hear it.

 

[tkent02]

I never heard a zap or anythng like it. Do what Agemax says.

 

[bigskybldr]

Agemax, I have pulled the battery off the bike and it still does it.
OldVet66, I'm pretty sure it's not the sound of a cooling engine. We all know the sound electricity makes when it arcs against something it shouldn't, that what it sounds like to me. I would think after 12 hours the engine would be as cooled down as it could be.

 

[rustybronco]

The stator is incapable of producing an arc with the engine not running.

 

[tkent02]

Can you record this zap for us?

 

[Agemax]

if the battery is disconnected it CANNOT be electrical. it has to be the engine cooling down. no other explanation.
engine fins can expand and contract slightly even with weather temperature changes

 

[Guest]

FYI, I have heard my bike do this from temperature changes after I open the garage door in the morning after the bike has cooled overnight. Think about it, since you obviously know the sound of an electrical discharge, what's the chances your electrical system would still be functioning after a massive discharge that would make that sharp single crack sound you are hearing. The stator wire windings are insulated with insulating varnish. A short arcing through wire like that would have it absolutely bare if not welded through by now, and there is nothing in that circuit that has the potential to do that when the bike is off.

 

[bigskybldr]

Thanks everyone, the bike has the carbs off right now so I'll try to pinpoint exactly what the sound is when I finish rebuilding them. I was worried I had some more problems brought on by the previous owner, he had some unusual fixes for anything he worked on. The latest is when I rebuilt the front caliper and master cylinder, all of the crush washers had been replaced with cutoff battery cable terminals apparently anything copper and has a hole in it should be good enough.

 

[allojohn]

Whip the cover off and have a look see. Who knows what PO's do. Set your mind at rest.

 

[bigskybldr]

allojohn..I think I'll do just that...I have some time to kill anyway(waiting for OEM needle valves and seats to come from Japan)
It's kind of funny, my wife about jumps through the ceiling when the bike makes this sound. She won't even go near it now...she's named the bike Christine(after the Stephen King novel)

 

[tkent02]

There are a lot of Christines...

 

[allojohn]

allojohn..I think I'll do just that...I have some time to kill anyway(waiting for OEM needle valves and seats to come from Japan)
It's kind of funny, my wife about jumps through the ceiling when the bike makes this sound. She won't even go near it now...she's named the bike Christine(after the Stephen King novel)

There are a lot of Christines...

LOL, I don't even want to think about that!

 

[chuck hahn]

Battery disconnected and it has sat cold for 12 hrs...theres no way that bike can be making any audible sounds. Even normal expansion and contraction from the days heat wouldn't make it make a loud zapping sound.

 

[bigskybldr]

Chuck the battery was still in the bike at that time. I know this doesn't make any sense, but the sound is coming from the bike. Oh by the way, thanks for the paint code Chuck my paint job turned out just as I hoped. Now I have a great looking bike....that makes strange sounds. lol