Spark Plugs

[Randy B]

I haven't touched my plugs at a tick over 18,000 miles, partly due to the EXCESSIVE cost of the plugs. I did find a better price than you did by quite a bit.

#11 in the pick list.

http://www.hondapartshouse.com/oemparts/...inder-head

[the Ferret]

good price! (If $15 for a single spark plug could ever be considered a good price)

[Cormanus]

My plugs were replaced, maybe at 24,000 kms. My recollection is that the mechanic thought it probably wasn't necessary.

They were expensive as I recall.

[the Ferret]

Ok just looked it up in the service manual

spark plugs: inspect at 4000 replace at 8000 inspect at 12,000 replace at 16,000 ect GADS!

BTW Tighten to 12 ft lbs is spec when replacing.

[Redbird_imp]

Hmm, I believe I will take some leeway here. Perhaps replace at a minimum of 12,000.
Back when I had my Valkyrie Honda said replace at 8,000. I replaced them at 24,000 just because. The bike was running fine.
You know, I just replaced the plugs in a 2002 Toyota Highlander at the recommended interval of 120,000 miles. They are iridium tipped and were only eight dollars and change each at Advance Auto Parts. Half the cost of the Honda plugs and 15 times the life before recommended replacement.

[Randy B]

The air cooled engine has something to do with it.

[flynrider]

The air cooled engine has something to do with it.

I suspect that the absurdly long nose is for better heat transfer from the cylinder head. Honda also put extra oil passages around the plug heads to improve cooling in that area.

Of course, my air cooled CB750 uses $5 standard sized plugs and no special oil passages for cooling, but combustion chamber temperature control was not that critical with the emission standards of 20 years ago.

[widude]

Thanks, great info. Plugs at $5 or $20 are till relatively cheap. No issues here, I like to upgrade plugs as called for when it calls for on replacement. That often calls for iridium on replacement.

I had a 2003 GMC truck, I had two upgrades to the original replacement plugs.

[Randy B]

The air cooled engine has something to do with it.

I suspect that the absurdly long nose is for better heat transfer from the cylinder head. Honda also put extra oil passages around the plug heads to improve cooling in that area.

Of course, my air cooled CB750 uses $5 standard sized plugs and no special oil passages for cooling, but combustion chamber temperature control was not that critical with the emission standards of 20 years ago.

I suspect that the absurdly long nose is for better heat transfer from the cylinder head. Honda also put extra oil passages around the plug heads to improve cooling in that area.

Of course, my air cooled CB750 uses $5 standard sized plugs and no special oil passages for cooling, but combustion chamber temperature control was not that critical with the emission standards of 20 years ago.
The oil was all about controlling the cylinder head temp to stabilize it for better emission regulation out of the engine. This is the only air cooled engine I have ever seen with a catalytic converter on it, and that is for a reason. The unpredictable and wide ranging head temps would make it so the converter would clog up in short order. With the oil passages in the head it helps keep things much more controlled and allows the bike to pass much tighter emission standards.

Fun stuff.

[Cormanus]

Somewhere on this forum there's a discussion about the likelihood that the plugs could be expected to survive much longer than 12,000 miles.