Bad Iridium Plug,first one !

[XS650D]

I have had my Iidium plugs in now since I purchased the bike approx 4-5 years ago.
I read that they last longer ,give better performance Yada Yada. Anyway I did notice that
compared to the standard NGK 7,s I did notice the bike idled and ran slightly smoother.
Was ou tday enjoying the fact that my bike no longer knocked (another post) but was running great!
Just as im pulling into the garage I noticed the bike sounded really loud,rattleing noises ,not good feeling.
Im thinking now what! Just when I got er dialled in and everything working rite. I left it running for a minute
and put on the centre stand and listening to were all the noise it coming from then I notice lots of white smoke comin out the shifter side pipe,Wow! Not good.Shut it down rite away and pulled the new filter, no metal all looks good, oil level good. So I decided to do a compression test and pulled out the shift side plug and notice its really wet. Pulled the clutch side plug and dry with good burn.Hmmm. Never had a plug go bad before other than a 2 stroke motor. So all I had was some original style NGK 7,s. So I pop them in let the bike cool down a bit maybe a hr and started back up, sounded good, went for a 5 min ride come back and pull the plugs, all dry and bikes run-in great again. Very strange but I guess I have a bad plug, thats a first.
Guess the plug wasn't igniting the fuel and being blown out the exhaust.May have washed the cylinder down a bit but I think it will be ok now.Will do a longer test tomorrow to be sure.Just another day with the xs!
I think I may leave the old style NGK,S for a bit.Whats a typical mileage for Bike plugs on this bike.
I guess its not like a car were they go forever!!

 

[TwoManyXS1Bs]

You *could* swap those iridium plugs, left/right, to confirm that it's the plug, and not some sort of carburetion anomaly...

 

[XS650D]

Just read an old post about plugs.Typically one side is neg and and other side positive draw.
So apparently one side gets much more wear. Yes I was going to do the swap then elected to
just install an old set that were still good.Will be doing a longer test today. U may be on to something as
the side that went bad has always been a problem carb .I think that a previous owner may have screwed the
fuel screw in to tight and damaged the internals. Never been able to get it to run same as the right side.
But its been that way for 4 -5 years and 10000 miles and plug never fouled!

 

[pamcopete]

When installed with a dual output coil, the funny thing about iridium spark plugs is that their superior performance depends on the center electrode getting very hot to "encourage" the electrons to jump across the gap. For those of you old enough to have experienced a tube type TV set you may recall that the cathode in the tubes was heated by a filament to "encourage" the electrons to go from the negative cathode to the positive plate.This is the same principle of the iridium spark plugs, so what that means is that only the spark plug with the negative voltage actually performs as intended. The dual output coil produces a positive voltage on one of the plug wires and a negative on the other.
Most modern cars also use a dual output coil with the same limitation, so that is why Ford Motor company installs two different spark plug types in their engines. One for the positive wire and the other for the negative wire. The advent of "coil in plug" technology eliminates this phenomena.
Of course, if you have a points ignition and the coils are wired with the correct polarity, you can have a negative voltage on both spark plug wires, but the puny voltage available from a points system is not enough to allow you to use a wider gap, another feature of an iridium spark plug.

 

[5twins]

I feel the old XS650 engine design and wimpy ignition is tough on plugs. I change them out every 3 to 4K and can usually detect some wear on them by then. To see it though, you need a new plug to compare the old one to side by side. The plugs burn clean and the edges of the electrodes stay relatively sharp, so wear is difficult to judge. What happens is the center electrode wears shorter over time, but very gradually. Comparing side by side to a new plug is often the only way you'll notice it. I just use the standard NGK BP7ES plugs, I don't use those fancy (expensive) ones. And with my dual output coil, it seems only one fancy plug might do any good anyway.

 

[XS650D]

Yeah! I decided to just stick with the basic stock NGK,S.