Spark plugs - how long will they really last?

[Bluey]

I change the plugs on my '99 1100 every 20,000 km's (the manual tells me 24,000 Km's). The old ones I take out are always still like new. no evidence of burning of the electrodes, no fouling of the insulators, just a slight overall discolouration. The gap is still at the 0.8 to 0.85 it was set to when installed.

Am I throwing out spark plugs that still have plenty of life left in them (it looks like it!)?

Has anybody just not bothered to change plugs, or extended the service period? Has anyone ever had problems with plugs failing?

Thoughts and comments welcome...

[saaz]

I changed over to Iridium plugs on the ST1100 when I got it, and they were good for 80,000kms plus easily. Many have left the standard plugs in for at least twice the recommended interval, as long as they look like yours. Starting seems to be where old plugs show their age, before there is any missing.

I had a fouling problem on one cylinder, and that meant I replaced the set of Iridiums at 80,000kms. That was more due to worn needle jets, so bike was running a bit rich.

[alans1100]

I'd say yes..........mine were done for the first time at 120,000 km (Jan 2011). It's possible they might have been done during the 11,500 km before I bought it in 2006 but I doubt it.

I put the standard plugs in and ran them for a little while. No real need to change them but I had iridium plugs sitting around so in May last year I put them in (162,500 km). Funny thing; the day I put them in was eight years to the day that I bought the 1100.

[Brock]

I have no idea what sort of plugs are in my bike, I pulled one from each side once to have a look. They were clean and working fine. My spread sheet shows no change in fuel usage and the bike still purrs like a kitten. My plugs have been in for 100,000 Ks or more.

like a lot of the "Planned Maintenance " on the 1100, if it aint broke dont fix it.

[Bluey]

Gentlemen, thank you all for these replies. Very informative.

I've just put a new set in (at 90,000) so I will check at 110,000 and if all looks well, check again at 130,000. (I service at 10,000 intervals - it's easier than trying to remember than 12,000 intervals - also means if I do go over my 10K interval, I don't have to worry for a couple of thousand k's)

Now, anyone want to buy several sets of hardly used ST1100 plugs??????

[Shaun]

I have yet to change a set of spark plugs on any bike, although I inspect them ever so often.

They always look tip top and the bike runs fine, so why change them. :)

[ST2UP]

Iridium plugs here too