What mileage interval are you getting on Plugs?

[fj09wildman]

What mileage on average are you changing plugs?
 
Service manual PM chart show 8K mi.s - 13K km/ Yearly.  First FI/ECU controlled bike for me and this just seems like it's a short plug life recommendation.  With most of my previous bikes the recommendations are to check gap, wear and color for burn characteristic's.  Thus, I would check plug gap, color looks good, runs good and gas mileage OK, reinstall and go. Mostly change plugs by judging the wear of the electrodes and performance.
 
What's the norm here?
 
Steve

[vespadaddy]

Personally, if I am going to bother to pull all the stuff off required to get to the plugs, blow out the plug recess with compressed air, and then snake the plug socket, extension, etc in there, I'm going to replace the with new plugs.

[traceroz]

Personally, if I am going to bother to pull all the stuff off required to get to the plugs, blow out the plug recess with compressed air, and then snake the plug socket, extension, etc in there, I'm going to replace the with new plugs.

Agreed.  It's a lot of effort to go to, and not change them.

[fj09wildman]

I agree. But was in there to retrieve a dropped screw. So I checked plugs. I would have replaced but none were available locally on a Sunday and I wanted to ride instead of wait. So I checked gaps and signs of worn electrodes. Both were OK. I have a box of 10 ordered for a on hand supply.
 
So now if you could answer my question. What mileage did you replace yours and you could add what condition were they in?
 
Steve
 

[wessie]

mine will be changed at 12,000 mile intervals, as detailed in my UK manual. We have 6k intervals, so every other service

[gregman]

8k miles is incredibly short for an FI bike (especially for a closed loop system like the FJ).
 
First off, let's talk about why you replace or service spark plugs. Two reasons. One, the spark plug physically erodes to the point where the gap is out of spec. This typically takes a really long time, and takes much longer with platinum or iridium plugs. Two, the plug accumulates carbon deposits and either fouls (bridges the gap between the electrodes, EXTREMELY unlikely in an FI engine), or builds up in the well around the insulator and changes the heat range of the plug (this would actually take, by far, the longest of the three scenarios here.
 
Carbon fouling is a real problem with a carbureted bike, since the air/fuel ratio will change drastically depending on altitude, humidity, etc. An open-loop FI system (no oxygen sensor) is only slightly better. A closed-loop FI system (O2 sensor in the exhaust) is much better, since the ECU gets air/fuel ratio information from the exhaust, and can change the fueling to compensate for altitude, humidity and other factors.
 
So really, with a bike like the FJ (closed loop FI), the primary concern is electrode erosion. Even with a standard, non-iridium NGK plug, I would expect 20-30k miles before the electrodes wear to the point that it causes a problem, and the first indicators would be skipping at idle and slightly reduced fuel economy. I feel like the manual is being way overzealous with an 8K replacement interval. Also, the nice thing is that you're really not going to break anything with a worn plug, so you don't have to worry about warranty issues if you extend the interval. Really the worst thing that could happen is the side electrode wears to the point where it melts and falls off, but that would take like 150-200k miles on a modern plug, and would be preceded by very poor running and detonation.
 
I'm at 8k now, and plan on balancing my throttle bodies next weekend. I'll pull the plugs while I have all that junk off and report back, but I bet they'll be just fine.

[wessie]

I think we have already concluded in the other thread about service intervals, that Yamaha's recommendations are based on market conditions to maximise workshop revenue than any engineering principle. Hence the shorter intervals in the US compared to Europe as the US consumer tends to be more anxious/gullible (delete whichever does not apply)

[fj09wildman]

Thanks Greg & I guess Wussie too. Like I said my first FI bike with O2 sensor. Just checking with you guys since it seems you get most of the bikes 2 yr.s before us (U.S.). I'll just delete both of the above Wuss ,if I may call you Wuss, if not just delete, because I like Greg's information/experience which is what I was looking for. I figure about 20K mi.s by the way the plugs looked when I checked them at 8K. I've got 18K mi's on mine now in 7 mo.s of riding 1/3 sport / 2/3 commute/touring. She purrs like a kitten and still jumps out of corners like a cougar. Trying to get plugs ordered for a descent price. Found a box of 10 of the standard NGK's for $4.50 ea. from my go to guy Dave but his vendor is being slow about it. Might have to bite the bullet and pay markup of 3 times that. I know there are some FZ-09 riders here on the board that may have some Kilo's/miles on their bikes and have changed their plugs. Thanks again for the info Greg.
 
Type @ U Later
Steve

[steve]

Mine will be changed next week at the 12k mile service. I am surprised at the low mileage (even though I'm riding 50% more than US between changes) at which they are being replaced. My carbed bikes were getting well over 20k miles per set.

[wessie]

Thanks Greg & I guess Wussie too. Like I said my first FI bike with O2 sensor. Just checking with you guys since it seems you get most of the bikes 2 yr.s before us (U.S.). I'll just delete both of the above Wuss ,if I may call you Wuss, if not just delete, because I like Greg's information/experience which is what I was looking for. I figure about 20K mi.s by the way the plugs looked when I checked them at 8K. I've got 18K mi's on mine now in 7 mo.s of riding 1/3 sport / 2/3 commute/touring. She purrs like a kitten and still jumps out of corners like a cougar. Trying to get plugs ordered for a descent price. Found a box of 10 of the standard NGK's for $4.50 ea. from my go to guy Dave but his vendor is being slow about it. Might have to bite the bullet and pay markup of 3 times that. I know there are some FZ-09 riders here on the board that may have some Kilo's/miles on their bikes and have changed their plugs. Thanks again for the info Greg. 
Type @ U Later
Steve

I'd prefer you to refer to me by my proper user name. Wuss is a pejorative word in my part of the English speaking world 

[Guest fzrcraig]

I'd prefer you to refer to me by my proper user name. Wuss is a pejorative word in my part of the English speaking world 

Your proper name must be "Dick" then.

[nhchris]

I just rolled past 8,000 miles and am checking the maintenance table in the manual.

What's strange to me is that my FJ manual gives the same replacement interval for spark plugs and oil filter:  8k miles.

That's awfully short for NGK plugs and seems really long for oil. I mean, who goes 8k before an oil change? And who changes the oil without changing the filter?

Is it me or them that's a bit batty?

Edited August 2, 2019 by nhchris

[betoney]

31 minutes ago, nhchris said:

I just rolled past 8,000 miles and am checking the maintenance table in the manual.

What's strange to me is that my FJ manual gives the same replacement interval for spark plugs and oil filter:  8k miles.

That's awfully short for NGK plugs and seems really long for oil. I mean, who goes 8k before an oil change? And who changes the oil without changing the filter?

Is it me or them that's a bit batty?

Yes, lots of crazy talk in the manual.  Personally, I have never changed plugs before 20,000 miles.  They get changed at the same time as the valve check - 23k - 25k just because the bike is already disassembled.