Spark Plug Replacement Interval

I've been fixing/riding bikes since 1962 In that time I have only had two spark plugs fail. First was in my new 1970 CB750 just 500 miles or so into my trip. Replaced it with a spare and completed the rest of my trip. Second was in a CB360 I rebuilt some eleven years ago. Wouldn't spark from new. Both failed plugs displayed no evidence anything was amiss...no fouling, no chipped insulator, no overheat/underheat indications, no eroded electrode....but neither would produce a spark. Both plugs were Honda recommended NGK's. This tells me that inspection alone is not sufficient unless you can verify a brilliant arc before reinstalling old plugs. If you do that, by all means go for it. I have been replacing plugs every 5000-8000 miles....no rocket science, just when I become bothered about them.
 
Jim Van said:
Mr. Bush :
It sounds like you don't want to believe the klitman's experience ( twice, no less ! ).
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That's not the case at all. Obviously a bike sold in not running condition has been very poorly maintained and who knows how old those plugs were? The fact that he took them out and cleaned them and they still didn't work, but new ones did, tells me they were in very bad shape indeed. Kiltman's experience has absolutely no relationship to how long a spark plug should last.

A spark plug can deliver a weak spark (or no spark at all) for a variety of reasons...defective coil, too much compression with incorrect plug gap, dry fouled or wet fouled spark plugs, insufficient ignition timing, etc. The size of the plug has no bearing on life either, as they all, no matter the size, have to operate within the same temperature range for optimum performance in any engine and to prevent engine damage.

Your original question was about that 8,000 mile change interval in the owner's manual. My answer as to the reason stands because, unless you have a poorly tuned engine, too rich or too lean, spark plugs should not need changing that often.
 
I buy my motorcycles used, and always do the usual maintenance first thing. I always wipe a dab of copper-color anti-sieze on the threads of the spark plugs when installing. I do the same for my truck/car. I have heard horror stories about stuck plugs, and for as seldom as I need to replace the plugs, it feels like a little bit of insurance. I am NOT saying to goop it all up, just wipe a dab and use your finger to cover all the threads.
 
Jim, since you're fanatical at preventative maintenance, and changing the plugs takes a few bucks and a few minutes, I'd have thought this was something you just did and never questioned it. But since you asked, put me down for one vote for Honda being overly conservative on their maintenance. My last change I put in Iridiums and its been so long ago I forgot when that was, but the bike still delivers 50mpg so I doubt they're in need of replacement.
 
kiltman said:
My 97 was offered for sale in a not running condition. The price was advertised $1350 Canadian. It was a California model with ABS, Corbin seat and PIAA driving lights as well as having a GVI top box. All I cared about was would it turn over. The battery was dead, I boosted it and it turned over. That's all I cared about as I suspected that all it needed was a good battery, carb cleaning, and new plugs. I ended up getting it for $1150. When I got it home I pulled the plugs, inspected them and made sure they were clean and properly gapped. It wouldn't start. I took a gamble put a fresh set of plugs in it and it started up right away. I was a happy camper. I then invested in changing fluids etc.
all this is anicdotal. I was just throwing it out there. YMMV
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Sounds like a steal to me, kiltman ! Nice buy !
 
dwalby said:
Jim, since you're fanatical at preventative maintenance, and changing the plugs takes a few bucks and a few minutes, I'd have thought this was something you just did and never questioned it. But since you asked, put me down for one vote for Honda being overly conservative on their maintenance. My last change I put in Iridiums and its been so long ago I forgot when that was, but the bike still delivers 50mpg so I doubt they're in need of replacement.
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Doug :

In 10K miles when I pull the Denso iridium plugs I will be installing soon, and if the center conductors haven't eroded like happened with the Autolites, I may re-install them for another 10K miles just to make Mr. Bush happy. But if they are eroded, I'll just put in standard NKG plugs every 10K miles.

p.s. And the extra timing belt guide I installed hasn't torn up my new timing belt ( yet ).
p.s.s. Can't wait to replace the clutch friction plates, clutch springs, u-joint, transmission output shaft seal, and alternator bearings this winter. You just can't over do with pm.
 
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Hibobb said:
I buy my motorcycles used, and always do the usual maintenance first thing. I always wipe a dab of copper-color anti-sieze on the threads of the spark plugs when installing. I do the same for my truck/car. I have heard horror stories about stuck plugs, and for as seldom as I need to replace the plugs, it feels like a little bit of insurance. I am NOT saying to goop it all up, just wipe a dab and use your finger to cover all the threads.
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:plus1: I've also been doing that that for years using "KOPR-KOTE". And I use it on just about every other bolt / nut on my vehicles.
 
Jim,

I have no doubt that you own some of the most meticulously maintained vehicles in the country . . and there is nothing wrong with that. What I don't understand and hope you can clarify for me is the income to costs ratio imbalance, as you have, on numerous occasions, mentioned being on a fixed income and have to look for the best prices on parts, even rebuilding your own water pump. If you are concerned with expenses, how do you rationalize throwing away perfectly good parts in your fanatical (Doug's adjective) preventative maintenance schedule? Answer me that and I will no longer question your PM obsession.
 
Mr. Bush :

First off , I must say I'm offended by your comment. I believe I may be the most meticulous owner in maintaining my vehicles in North America, not just in the USA !! And it's not an obsession, it's a philosophy.

But seriously ( seriously ) , Since I do my own work, I can afford spending a bit on parts ( if I shop for the best prices ) and doing as much as I can to reduce maintenance costs, like rebuilding my water pump - why not ? And keeping a vehicle running good helps gas mileage and from possibly breaking down on the road ( towing costs ). This keeps the frustration level down and possibly early replacement ( depreciation savings ).

To tell you the truth, I test rode a used K1600GTL a few years ago - nice riding bike. No overall comparison to my ST1100, except that on the slab it wasn't any smoother or comfortable, with the farkles I have installed on my old ST1100 ; home-brew handlebar risers, RDL seat, a foot peg lowering kit, RaceTech Gold Valve & Emulator kit, RaceTech front springs, Progressive rear shock/spring , and front fork brace. With regularly rebuilt calipers, kevlar brake pads and Brembo 12 mm front master cylinder, it stops good enough for me. I certainly wouldn't be gaining much for an extra $18K ( USD ). And it's kinda cool doing LD rides with the oldest bike in the group. I just did an IBA Lake Superior SS1K with a guy on a '16 R1200RT.

So, I don't mind spending a few $$ for pm to have well performing & reliable ride. I'm on a fixed income, I can't afford any large or unplanned expense.

EDIT : My friend on the R1200RT has a set of $1,050 Clearwater LED spotlights. I have a set of $200 Superbright LED work spotlights on my bike. I could hardly see the $850 difference, BTW.
 
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Just for the record, when I used the term 'fanatical' it was not meant in a negative or durogatory sense, but it seemed be a good adjective to describe Jim's philosophy towards maintenance. I don't think he took it as a negative comment, but just wanted to make sure it wasn't misinterpreted.
 
Thanks for the reply to my question Jim and I can sleep better now knowing that you won't be putting yourself in the poor house by continuing with your "philosophy". It's just too bad I don't live closer to you though, as I could take some of those good, slightly used parts off your hands for you! :)

Carry on maintaining!
 
Mr. Bush :

Would you like a set of clutch friction plates, clutch springs and a u-joint with only 90K miles on them ? Just pay for the postage. And since I'm a nice guy, I'll pay the postage for the used transmission output seal. If I'm going to remove the swing arm to grease the swing arm bearings and service the alternator, I might as well replace the transmission output shaft seal, what the heck !
 
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dwalby said:
Just for the record, when I used the term 'fanatical' it was not meant in a negative or durogatory sense, but it seemed be a good adjective to describe Jim's philosophy towards maintenance. I don't think he took it as a negative comment, but just wanted to make sure it wasn't misinterpreted.
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Doug : I took that comment a high compliment ! I am a fanatic when it comes to preventative maintenance. Thank you.
 
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