Member Contributer Grum Posted December 6, 2018 Member Contributer Share Posted December 6, 2018 Hi All Interesting Info - Speaking only for NGK Plugs, both 6 and 8gen plugs appear to be exactly the same spec however the 6gen are IMR9B-9H and the 8gen are IMR9D-9H. These are both very long life Platinum (Ground Electrode) Iridium (Center Positive Electrode) plugs which NGK state have a longevity of 100,000 miles!!!! Both 6 & 8gen Maintenance Schedule states to replace at 48,000k's or 30,000miles! I have a set of IMR9B-9H's from a friends 6gen having done 70,000k's. The electrode gap was still .035in and the plugs looked in good condition, there were no issues with his bike prior to replacing them. Today out of curiosity I removed the plug from cylinder 1 on my 8gen having done 60,000k's (see attached pic) the plug looked fine and the gap was still .035in as per the brand new one. I won't be in any rush to replace them. NGK advise me they are made to exceed Honda's spec and only recommend them to be replaced per the Honda Maintenance Schedule purely for Warranty reasons, other than for that reason they mentioned 100,000ks should be no problem. - Any thoughts? Link to comment Share on other sites More sharing options...
Member Contributer Stray Posted December 6, 2018 Member Contributer Share Posted December 6, 2018 Yup, iridium plugs are designed to do 100k. Some guys get 150k out of a set - depends on your bike’s state of tune. Even iridium electrides eventually erode, although they are remarkably resilient. The electrode is ultra fine compared to a standard plug and concentrates the spark. The corners are where plugs wear out. If you hold a plug upside down (ceramic facing down and business-end facing up) the electrode has a flat top like a table. The corners of that table are the first to erode. New plugs have a nice crisp tabletop: old plugs have a rounded electrode that looks more like a bullet tip. Your iridium plugs might still have the correct gap but the edges of the tabletop may have got rounded with time. Also, because the tip is so fine it is difficult to tell just how eroded the corners of the tabletop are. Look really closely with a magnifying glass at yours. Having said all that iridium are incredibly long-lasting plugs and you should easily see 100k from a set. I’m curious why there is a different plug for each gen? Head should be sane, no? 5th gen: CR9EHIX-9 6216 6th gen: IMR9B-9H 8th: IMR9D-9H Far as I can tell the CR9EHiX has a slightly shorter threaded section than the IMR9B-9H. I wonder what the “D” stands for in IMR0D-9H? I’m really wondering if we should all be using the 8th gen plug IMR0D-9H? Technology improves and gets refined with time. Honda isn’t going to send out a retrospective bulletin telling all 5th/6th gen owners that IMR0D-9H is a better plug for their bikes than the one specified in the manual 20 years ago, is it? Just like some older bikes specify basic plugs and dyno oil in the manual but owners gain benefit from iridium plugs and synthetic oils nowadays. Stray Link to comment Share on other sites More sharing options...
Member Contributer thtanner Posted December 6, 2018 Member Contributer Share Posted December 6, 2018 4 hours ago, Stray said: Yup, iridium plugs are designed to do 100k. Some guys get 150k out of a set - depends on your bike’s state of tune. Even iridium electrides eventually erode, although they are remarkably resilient. The electrode is ultra fine compared to a standard plug and concentrates the spark. The corners are where plugs wear out. If you hold a plug upside down (ceramic facing down and business-end facing up) the electrode has a flat top like a table. The corners of that table are the first to erode. New plugs have a nice crisp tabletop: old plugs have a rounded electrode that looks more like a bullet tip. Your iridium plugs might still have the correct gap but the edges of the tabletop may have got rounded with time. Also, because the tip is so fine it is difficult to tell just how eroded the corners of the tabletop are. Look really closely with a magnifying glass at yours. Having said all that iridium are incredibly long-lasting plugs and you should easily see 100k from a set. I’m curious why there is a different plug for each gen? Head should be sane, no? 5th gen: CR9EHIX-9 6216 6th gen: IMR9B-9H 8th: IMR9D-9H Far as I can tell the CR9EHiX has a slightly shorter threaded section than the IMR9B-9H. I wonder what the “D” stands for in IMR0D-9H? I’m really wondering if we should all be using the 8th gen plug IMR0D-9H? Technology improves and gets refined with time. Honda isn’t going to send out a retrospective bulletin telling all 5th/6th gen owners that IMR0D-9H is a better plug for their bikes than the one specified in the manual 20 years ago, is it? Just like some older bikes specify basic plugs and dyno oil in the manual but owners gain benefit from iridium plugs and synthetic oils nowadays. Stray No you should not use the 8th gen plugs in the 6th gen. Use the ones specified for 6th. While very similar, the 8g engine has enough modifications to be a different animal. They'd work fine, they're darn near the same plug. Just don't expect any performance increase what-so-ever tbh. IMR9B-9H & IMR9D-9H share the same specs 100% aside from the plug being "projected" https://www.ngk.com.au/technical_info/projection/ I change Iridium plugs @ 50k on bikes, 100k on cars. Link to comment Share on other sites More sharing options...
Member Contributer MaxSwell Posted December 6, 2018 Member Contributer Share Posted December 6, 2018 I had my 2001 in for service over last summer and a spark plug check was part of the service. At 65,000 mi. they were still as-new. One has to love those iridiums. Link to comment Share on other sites More sharing options...
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