Spark plug observations
 

When I got my used 650K6 from the dealer, they gave it a full service, including new, standard NGK plugs. After about 6,000 miles (mostly brisk open-road riding, almost no town work) I replaced them with a set of Iridiums.

The standard plugs were pretty much unworn, gap was about 30thou / 0.75mm.

During the week I thought I'd have a look at the Iridiums as they'd done 8,500 miles of the same type of riding. Again, zero electrode wear and no sign of wear elsewhere, gap was still bang on the 0.7mm which I'd set them at.

So the moral of the story is: SV650s seem to give their spark plugs an easy life.

Re: Spark plug observations
 

Mine get replaced at 20,000 miles

Re: Spark plug observations
 

I tried a set of Iridiums in my Curvy and they seemed a little flat in response and ran a little lean.I could have adjust the fuel mix but couldn't bothered so stuck the supplied Denso plugs back and all good again.

YMMV

HTH :)

Re: Spark plug observations
 

Normally iridium plugs will last 70 to 75,000 miles in a car (or over 120,000 if you believe what you read in American Forums :rolleyes: ), so motorbikes definitely harder on plugs than a car. The iridium tip resists the heat and spark erosion much better and are supposed to 'focus' the spark better due to smaller diameter of the tip, my wifes Honda Jazz uses 'double iridium' plugs where both the centre and ground electrodes are iridium as opposed to just centre electrode on most plugs, but they are pricey :(

Re: Spark plug observations
 

with spark plugs its not just the tips that erode. spark plugs can look fine but the resistance breaks down, which is the biggest cause of spark plug failure.

Re: Spark plug observations
 

Yes, although I've never had a spark plug resistor fail as yet ... however I have had resistors in the plug caps fail.

On my old GT380 I used to use platinum plugs (later replaced with Iridiums) and non-resistor caps, and they never, ever needed re-gapping or cleaning. Used to give the tired old ignition system a helping hand :)

Re: Spark plug observations
 

I have never had an integral spark plug resistor fail either (on NGK there is an 'R' in the plug number for resistor), the gap is the main thing, because as that gets bigger the coil has to produce more voltage to jump the gap and very often the higher voltage can make a coil insulation break over internally and fail. Iridium and platinum plugs need less voltage anyway because finer tip makes it easier to produce a spark and give everything in ignition circuit an easier life.

Re: Spark plug observations
 

Re: Spark plug observations
 

The guy who wrote the article is a bit suspect on electrical knowledge, he states that iridium has higher electrical resistance than copper and will degrade performance, the spark is high voltage low current, so a few extra ohms is neither here or there. Copper core is used for cooling / good heat transfer away from tip into body of plug, not electrical conductivity, otherwise why would plug maker fit a resistor into plug body - iridium plugs still have copper alloy core with iridium tip laser welded onto end to resist spark erosion.

Re: Spark plug observations
 

Yes but in your previous post you made a point of saying that the lower resistance of Iridium would be beneficial which is fact incorrect as Iridium has a higher resistance.

Also resistors are fitted to Spark plugs to suppress Back EMF from interfering with the ignition circuit.