backfire on startup?

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Hi,

This morning, I had trouble starting the bike, which is very unusual.  I had to attempt to start her up 3-4 times and started smelling a hint of gas.  Anyway, on the last one, there was a VERY loud explosion that scared the heck out of me.  Then I attempted to start and it ran fine.  What could've caused this and how can I prevent it in the future.   This can't be good....and I probably scared all my neighbors to death.

[gsJack]

Heard the big bang quite a few times when my 02 GS was missfiring on the #1 cylinder last winter and into spring when damp.  Problem was a loose coil wire connection at the coil.  When the gas in a cylinder isn't burned it collects in the exhaust and then a spark will set it all off at once.

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gsJack,

Can you elaborate more on where this loose connection was and how you narrowed it down to it?  Should I start checking for good spark etc. to diagnose this?

Thanks!

[gsJack]

Must have posted on this before, found this pic in my Photobucket:



The spark plug wire screws into the front of the coil onto a little brass post that's in a c'bore cast in the front of the coil.  Besides screwing in it must be cemented or bonded in there too because when new you can't budge them when twisting the wire.  Coil and wire are sold as one piece.  These connections become loose in time and spark can jump out of there when damp and cause misfiring.

First had a problem spring of 06 and discovered the loose wire then.  Cut half inch off wire and screwed it in tight and it was good some 10-12k miles till this spring.  Putting a good squirt of diaelectric grease into the c'bore before screwing wire in helps much.  I've since replaced the wire and all is well for this year.  Got a 6' length of wire from Dennis Kirk so I can replace as necessary in future and will check when I do valves.

So I checked the old 97 GS with 80k miles on it parked in the garage and found both wires loose, could just grab them and pull them straight out w/o unscrewing.

The problem is missfiring of a cylinder and your problem could be elsewhere, but the loose coil wire could be a good place to start looking

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Thanks again gsJack!  I'll go ahead and check those connections.  Any other checks that you or anyone else can think of?

[Jughead]

Well I guess I can Put my Preaching In.If you still have Problems After you take Care of What GS Jack Has Explained (Also Cut the Wire 1/4 of an Inch so when you Thread the Wire Back onto the Screw you will Get a Good Bite.) The First thing I would do is Ditch the Original Spark Plug Caps.They have an Internal Resistor that Could Possibly Build up Resistance over time.If you do replace them Go with New NGK Non Resistor Plug Caps.I don't have the Part Number but your Local Dealer Should Be Able to Help.
Also If you are Running Resistor Plugs ditch them and Get Non Resistor Plugs.With Resistor Plugs and Resistor Caps you will be running too Much Resistance and won't be getting Enough Spark to get a Complete Burn.After Replacing the Resistor Plug Caps with Non Resistor Caps you can run Resistor Plugs and Accomplish the Same thing as the Resistor Caps did but it is Totally Unnessacary unless you ride down the Road Listening to the Radio.The Resistence is only Put there to Cut down on Radio Interferrence.