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Spark Plug replacement frequency

AlanNZ

AlanNZ

Cruisin' Guzzisti
GT Contributor
Joined
Sep 20, 2013
Messages
227
Location
Auckland
Do others religiously change their stock plugs at 10,000 km (6,000 miles)? I have been - but they always look good and are performing well when I change them. I'm wondering if I should stretch replacement intervals out?
The Stelvio plugs (standard NGKs) are a bit more expensive than my other Guzzis.
Alan NZ
 
I would recommend inspecting the plugs at that interval. Check the gap then adjust if necessary. I've run plugs over 40 K miles with no issues.
 
On my Griso 1100 there are two different plugs. The outer plugs are a normal plug and I change them at normal plug intervals, I go more than 6,000 miles but if you want to throw plugs at it you can. The inner plugs are high dollar platinum plugs and they should be good for a very long time, perhaps you may never need to change them. I still change them, but I did not change the inner plugs until around 50,000 miles. That was probably too soon but I had things apart and figured while I was in there.....
 
On the '00-05 bikes using the 15M ECU, recommended plug replacement was every 3k miles. The bikes idled better and had better throttle response with new plugs at that interval, no matter what they visually looked like.
The newer bikes seem to do a great deal better, so I usually replace them at either 6 or 10k depending on your chosen service intervals; Mine are every 5k miles, so I change them every other or every 10k miles. The 8V's have an extended life plug, so I'll probably stick to the recommended service interval. Also worthy of note, I spoke with NGK this week, and they said they strongly do not recommend any other of their plugs in place of the PMR8B on the 8V.
 
GT-Rx® said:
......The 8V's have an extended life plug, so I'll probably stick to the recommended service interval. Also worthy of note, I spoke with NGK this week, and they said they strongly do not recommend any other of their plugs in place of the PMR8B on the 8V.
Click to expand...
I have been using NGK CR8EKB in my '13 NTX which is what is quoted in the manual. Is the PMR8B a replacement for this plug?
Regards
Alan NZ
 
THe CR8EKB is the recommended plug (Stock) for the MY11+ NTX (ie. newer model). The PMR8B is was the stock plug on the older NTX's. The CR8 is a dual electrode plug so it cannot be gapped (at least not accurately). The PMR8B is a single electrode plug. I change mine every 10K Km. They are not that expensive, at least not here.
 
I changed the ones in my 09 at around 23,000 miles. I am around 46,000 miles now. The plugs looked great on the first change and likely could do a lot more miles.
I of course inspect and gap them if needed at every valve adjustment/inspection, which I do around 10,000 miles.

My older 2 valve Californias I would inspect and often change at the valve adjustment, also near the 10,000 mile mark.

BUT, I had forgotten to change them out once on my hydraulic lifter EV. I had about 30,000 miles on the plugs when I notice the bike was getting hard to start. It turns out that the electrode was a good bit eroded.

Of course the unobtainium metals used in the Stelvio spark plug SHOULD last a good bit longer than 30,000 miles.
 
GT-Rx® said:
On the '00-05 bikes using the 15M ECU, recommended plug replacement was every 3k miles. The bikes idled better and had better throttle response with new plugs at that interval, no matter what they visually looked like.
The newer bikes seem to do a great deal better, so I usually replace them at either 6 or 10k depending on your chosen service intervals; Mine are every 5k miles, so I change them every other or every 10k miles. The 8V's have an extended life plug, so I'll probably stick to the recommended service interval. Also worthy of note, I spoke with NGK this week, and they said they strongly do not recommend any other of their plugs in place of the PMR8B on the 8V.
Click to expand...
Todd. The workshop manual for the later Stelvio states the plugs are long life but it also states replace them at 10,000 km. The owners handbook states the same. 10,000 km replacement does not seem to be long life to me? I wonder what NGK recommend?
Regards
Alan NZ
 
AlanNZ said:
I have been using NGK CR8EKB in my '13 NTX which is what is quoted in the manual. Is the PMR8B a replacement for this plug?
Regards
Alan NZ
Click to expand...


I went to cycle gear for new plugs for my 13 Stelvio and was told the NGK CR8EK without the B at the end was they carried and that it was the same..I bought them and compared and they them to my stock plugs and see no difference. any ideas what the B stands for?
 
I thought the only difference was the screw on connector on top vs a fixed connector?
Alan NZ
 
I had no idea and neither did the cycle gear guy but that makes sense, luckily I had some new NGK plugs from my dirtbike that had the tops and was able to use them for my Guzzi. Am I right to assume these come pre gapped?
 
A bad plug can sneak up on you!

I've outlined this earlier on this website.

At about 20,000 miles, my Stelvio developed an annoying stumble at about 3000 rpm when the engine was under labor. I checked everything- valve lash, fueling, throttle synch, you name it. I had looked at the spark plugs and they looked like new. Steve had left Riders Hill but Ian checked it out and found nothing.

As a last ditch effort, I replaced the spark plugs and the problem was immediately cleared up! Despite looking fine, there must have been a problem internal to one of the original plugs.
 
leafman60 said:
A bad plug can sneak up on you!

I've outlined this earlier on this website.

At about 20,000 miles, my Stelvio developed an annoying stumble at about 3000 rpm when the engine was under labor. I checked everything- valve lash, fueling, throttle synch, you name it. I had looked at the spark plugs and they looked like new. Steve had left Riders Hill but Ian checked it out and found nothing.

As a last ditch effort, I replaced the spark plugs and the problem was immediately cleared up! Despite looking fine, there must have been a problem internal to one of the original plugs.
Click to expand...
We're the plugs 20,000 miles old when it happened? That's much more than the recommended 6,000 miles replacement in the manual -which seems excessive to me.
 
AlanNZ said:
We're the plugs 20,000 miles old when it happened? That's much more than the recommended 6,000 miles replacement in the manual -which seems excessive to me.
Click to expand...

Yes, yes but I thought I knew better than the manual! lol

That's my point.

I still can't imagine modern spark plugs having to be changed every 6000 miles. The plugs in automobiles often go for 100,000 miles, plus.

I think I just had a defective plug.
 
For what it's worth, I sold my spark plug cleaner.
I used to do frequent "plug chops" on vintage stuff just to check the mixture.
Plugs are cheap enough that it's not worth the effort cleaning them, and the possibility for abrasive residue was too great.


Leafman, perhaps with a two cyl cycle a weak plug is more noticeable. You might have one weak plug in a 4-6-8 cyl auto and never notice. I recently had the plugs changed in my 6 cyl sedan. Didn't notice a change, but I felt better. I asked for the old plugs back (they had 60k) and actually they looked fine.

So...I've got no answers.
 
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