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Spark plugs

10K views 20 replies 13 participants last post by  cyclerama 
#1 ·
So today I pulled off my tank thanks to the great sticky here - I changed out my air filter and pulled my rear spark plugs to change. Then I got the wires off and pulled the plugs the little cap stayed inside the rubber wire cover. I just took the one off the new plug before seating it and it seems to fire fine.

Is this a problem though?

I was surprised to see the plugs were iridium, so I can't figure out for the life of me why they have a 12000km service interval! They had some corrosion and carbon build up but gapped okay so I'm not too worried about replacing the front plugs which seems more of a hassle.
 
#3 ·
Unless the engine is REALLY hard on plugs, and I really doubt it, iridium plugs are usually good for seventy five thousand Ks or thereabouts. They might wear out sooner if you flog the engine, use crap fuel and generally abuse the bike ... but I can't see them going south in 12,000KMs.
 
#4 ·
I wouldn't think 12000 kms would be enough to affect any plug let alone an Iridium. I still think in miles so that equates to about 7500 miles. I'll have to check my manual to confirm what you said as I find that much too soon.

I think a more realistic time to change them would be when the valve adjust check/adjustment is done around the 24000 Km mark.
 
#6 ·
Iridium is better than platinum, but a lot less of it is used. The smaller center electrode is less durable than platinum- the sharp edge around the periphery is rounded off faster. It's the sharp edge that is the magic, and you're not likely to notice much of a gap change, depending on the construction of the outer electrode.

The recommended change interval does seem overly conservative for even 0.4mm electrodes, but I don't think expecting 75,000 miles is a reasonable expectation. The recommended interval may have to do with emissions regs requiring optimum lean starts and a lean idle. I'll inspect my plugs at the first valve check and change them at 30,000 regardless of how they look, unless I notice harder starts or missing at high throttle and lower RPMs.


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#7 ·
I don't think expecting 75,000 miles is a reasonable expectation. The recommended interval may have to do with emissions regs requiring optimum lean starts and a lean idle. I'll inspect my plugs at the first valve check and change them at 30,000 regardless of how they look, unless I notice harder starts or missing at high throttle and lower RPMs.


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I said 75,000 Kilometres, not miles. That's a bit under 47,000 miles. I also said it would depend on the exact conditions the engine was running under.
 
#10 ·
No problem. :thumbup:

12,000KM is a ridiculously short interval for iridium plugs imho. For regular plugs, fine, for iridium, no. My old GT550 used regular plugs and only needed refreshing at about 20,000KM intervals IF I'd been giving it a hard time ... which I usually did :fineprint: but even then it didn't make much difference if any (phantom butt-dyno effect). The plugs always looked fine and the gaps would check just fine as well. The also only cost about $3.50AUD each so it was no big thing.

I wouldn't be surprised if the change interval was set with regular plugs and then iridium was substituted to help pass emissions testing.
 
#9 ·
I checked the manual and the Suzuki recommended maintenance service sheet and yes they recommend them to be changed at 12000 KM or every 24 months. Seems a little short to me but will watch the performance aspect and see what issues start to develop.

I'll probably just look at this one as a yearly maintenance item, like bleeding brakes, lubing cables etc and do it myself during the winter months.
 
#11 ·
Most of my bikes have 8,000 mile intervals, I pushed an FJR to 26K till the bike was struggling to start. So the "good" plugs will go at least double the recommended miles. In that bike a 24K interval was wise, the engine got noticeably rough after 25K.

The only bikes I've had that were easy on spark plugs are my DR650 and the Honda ST1100 which never seemed to need plugs.
 
#12 ·
My 2005 wee had a recommended plug change at 24 000km. Same for the air filter. They were regular plugs and only one per cylinder. The recommended plug change on the new wee is way to soon, considering there is two per cylinder and they are iridium. I intend to change the air filter at 24 000KM intervals on my 2013, as I did on my 2005. I will then take advantage of the fact that the gas tank is off to check the state of the plugs. But I am convinced I will not have to change them. Plugs now last up to 100 000 km on newer cars. So, 12 000?.....yeah, right!
 
#13 ·
Plugs on the Glee are Iridium types besides. Maybe change them at a valve clearance check at some future time.
 
#14 · (Edited)
Changed mine with valve check, 25,000km (15500 miles) They did show wear, however definitely plenty of life in them. Just a convenient time to change together with the air filter. With higher rpm, would not expect plugs to last anywhere near what we get on cars.
 
#17 ·
I will say car plugs fire much less often. That being said, I expect Iridiums to last 50,000 miles easily on a V-Strom.
 
#20 ·
I changed the platinum spark plugs (AC) on my truck a few weeks ago and they had a blob of material on the tip of the ground bend and 3 of the 6 were gone. This made the gap .075" instead of .060" so I'm not so sure where it went and the quality of the plugs.

I put iridiums in instead.
 
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