Ok, a couple of nights ago I was starting up my bike, I had just hit the starter button when the bike made a little pop/bang noise and emitted a puff of grey smoke from under the left hand side of the seat, about where the battery is, near the fuel reserve switch.
It didn't start up because I took my thumb off the starter before it could turn over.

I looked under the seat and couldn't see anything burn or scorched, so I tried starting it again, and this time it went Ok. I've done about a hundred kms, and started the bike a few times, and it hasn't happened again.
I was just wondering if anyone knew what might have caused this, because I have nfi  :dunno:
And I'm a bit worried that I've missed the problem and it going to come back and bite me.  

cheers  

OK My guess is battery positive somehow contacted the frame or somehting.
Cool.
Srinath.

Had you recently charged the battery?
That has happened to me when I left the charger on and cranked the bike immediately after. When those batteries charge, they emit hydrogen from the water in the cells, very explosive . I always make it a habit to fan away the battery right after charging it as a result of my prior experience.

Hope this helps  

Good tip, Casi!

Tell us more about the "grey smoke".  Did it smell "electrical", or like fuel, or what?

Might wanna check any fuses under there.  A friend of mine had a V75 magna that had the same thing happen.  I forgot what the fuse was called but it got blown in half.  Good luck

The whole bike runs on a single fuse.  See a picture of its location HERE.

Quote from: KerryThe whole bike runs on a single fuse.  See a picture of its location HERE.

yup..that's it.  

My main point being that, since he has "started the bike a few times" since the BANG, it probably wasn't the fuse.

But if you didn't know the bike had only one fuse, that was a great suggestion.  

Quote from: KerryMy main point being that, since he has "started the bike a few times" since the BANG, it probably wasn't the fuse.

But if you didn't know the bike had only one fuse, that was a great suggestion.  

no i did not know a bike only has one fuse.  My friend's started back again also, that's why I suggested it.  Upon closer look,  the fuse was still touching that's why it started but eventually it just blew after a few restarts.  I'm no mechanic nor know anything about bikes....I just thought i'd share something similar that happened.  :dunno:

it seemed like an "electrical" bang to me, not fuel.

i hadn't charged the battery, but the bike had been sitting for several days in the garage, so I think CasiCUA's idea of hydrogen from the battery being ignited sounds like a good explanation.

Does the battery have a breather hose at all? or a vent?

I checked the positive terminal of the battery, and the cabling around there first, and nothing is worn, and the terminal still has it's rubber cover, so I don't think that it was a short.

Anyway, it all seems Ok now.  

Quote from: panikDoes the battery have a breather hose at all? or a vent?

Yes.  The stock battery has a vent hose that attaches on the right side of the battery and then drops down next to the battery box.  It come out near your right-side footpeg.

If you have an aftermarket battery the vent might be on the LEFT side, and since the vent hose isn't really long enough to reach across the bike someone may have just left the vent open.

One possible solution (IF that's the case):


This particular listing is from the Chaparral printed catalog.  See the online listing HERE.

Could also have been a backfiring into the carboretor. These things do happen.

The puff of smoke then would have been dust from the air filter.

Here is another possibility. The gas may have seeped into the starter solenoid and been ignited by the arc generated across the contacts when you tried to start it.

Funny you should write this, exactly the same thing happened to me a week ago and I also couldn't find any scorch marks or anything. The bike has been fine since but the first couple of rides were uncomfortable, listening for every sound.

Dudes!
That is a good discription of a backfire thru the intake system or stackfire.  It happens when ignition of the mixture is somehow delayed.  Then the intake valve opens again and it fires thru the intake system.  Posible causes could be:  too high an octane fuel, improper cam timing, improper ignition timing, improper valve sealing, worn engine parts, worn ignition parts, etc...

im thinkin backfire thru carb, cause the whole  explanation points it out?, cause the air box inlet is in the general area... :dunno: