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Old 11-29-2012, 09:39 AM   #16
cycleman2
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I've run Iridium plugs in other motorcycle engines and they do make a difference in driveability. You should be able to find the cross reference you need and they are certainly worth a try. I wouldn't worry too much about adding the 5k plug resistance to the plug wire resistance, with the Iridium's narrower plug tip, they don't take as much voltage to fire.

I used them in some first generation Goldwing's which had point ignition with no issues. I also currently use them in my Harley and there is a noticeable difference ( to the better ) between them and the stock plugs.

So go ahead and try them.
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Old 11-29-2012, 01:17 PM   #17
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+1 for cycleman's explanation and results.

Others have had similar results even documenting a 2hp gain on Yamaha xs650 and 750s on dynojet testing (see http://www.xs650direct.com/products-27.html site).

As the xs engine has a similar combustion camber shape as the airhead I thought it would be worth a try. Yes the plug is expensive but if it extends the service life and if it improves the engine performance even marginally it would be worth the extra cost. The reduced voltage required to fire a "pin" type electrode should provide reduced fouling and improved starting (or so the theory goes).

While cycleman may well be right about not worrying about the plugs built in 5k resistance, I tend to like to duplicate the original ignition specs as closely as possible so as not to stress the coils.

Just my thoughts and I'm no expert.
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Old 11-30-2012, 04:17 PM   #18
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ebay price is $25ea .. ouch... checked Oriellys who had em for $7 ea
for $15, I'll give em a try ...

BMW R80GS R80ST R80RT R80 ngk IRIDIUM spark plug 6637
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Old 11-30-2012, 06:36 PM   #19
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Not running 5k resistance caps isn't about the coils. It's about the ICU and hall effect sensor. Running less resistance IS hard on them.

I run them in my truck but I only change plugs every 100k miles. Other than that I have my doubts about any performance change. I have never noticed any difference running platnum or whatnot. I sure didn't notice any difference with split fires but that fad seem to be over. In my bike? I had just as soon change regular plugs versus cleaning longer lasting ones. The crude WILL build up on them!
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Old 11-30-2012, 06:47 PM   #20
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The only time I ever had exposure to Iridium spark plugs was on De Havilland Beavers or high performance Twins back when I started my aviation wrenching career. Performance enhancement? I didn't believe this was the reason that we used them. It was merely to improve serviceability on these engines between scheduled maintenance checks. Standard plugs would erode severely between the 100 hour intervals that existed between plug removal and testing. Many times the rear plugs on the Pratt & Whitney 985's would be seized and removal might mean the damaging of the cylinder head/spark plug holes - best to leave them in and look with a flashlight through the front plug hole and see how they were doing.... Throw some Iridiums in the back plug hole and things held together longer. On the high performance horizontally opposed engine end of things, the bottom plugs would always get covered with all the junk - just the same way our dual plugged Beemers do in their much easier working environment. So all you folks who think that you're creating a race machine by throwing in these plugs, by all means do so. I'll carry on running my NGK's which never seem to erode at all.....
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Old 11-30-2012, 07:20 PM   #21
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I have been running NGK iridium plugs in my 1983 R80ST for years now. Haven't touched them except for valve adjustments and they still look great. Much easier to start than before, and they never seem to load up. Best improvement for the money so far.
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Old 11-30-2012, 07:20 PM   #22
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I use Iridium plugs in my 72 Bonneville and also my 70 BSA Royal Star. With non-resister caps. The Bonnie has a Boyer, the BSA, points. For both bikes the recommended plugs are Champion N3 and N4's respectively. I too was skeptical about any performance enhancements, but was told to give it a try by a Brit bike guru. Sure enough, both bikes have seen an improvement in starting, idle and cleaner running with less fouling. They have been problem free. For me, it's worth the few extra bucks.
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Old 11-30-2012, 07:43 PM   #23
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I just run NGK BP8ES plugs - I buy them cheap at NAPA using my discount. The plugs I pull out of my GS are clean and un-worn - I change them every year but for no good reason. They could go right back in and perform many years of service ongoing. It idles nicely. It runs well at speed. It always starts but that I put down to the carbs being re-built correctly by myself several years ago.
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Old 11-30-2012, 09:45 PM   #24
pommie john
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I tried iridium plugs in my Norton Commando race bike. On the dyno they showed about 1 horsepower improvement throughout the range.
However.. my drag racing guru friend reckons that if you get a gain from something like different plugs, there's a fair chance that your ignition system is the real problem. You might have a coil on the way out or other HT problem.
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Old 12-01-2012, 04:24 PM   #25
cycleman2
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If you do some research on the web on Iridium Spark Plugs you'll find a pretty consistent 1 or 2 hp gain in most applications. My view of why that is happening is that using them has the same effect as advancing the timing slightly, with no knock conditions.

They do work and are worth a try. Lots of nay sayers but go ahead and try them, you'll be pleasantly surprised.
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Old 12-01-2012, 05:25 PM   #26
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I have heard the same stories with all sorts of new plug designs. Remember tons of people reporting all kinds of advantages running Autolite plugs in oilheads? It just wasn't so. Still isn't!

Tracking one hp gains is more complicted than swapping plugs for another run. Oil temps and engine temps need to be duplicated not to mention tire temps and traction and that's just the tip of the iceberg. All that takes time and equipment that most for one reason or another don't have. It's hard enough on an engine dyno, let alone wheel dyno's.
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Old 12-01-2012, 08:15 PM   #27
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How many airhead riders are going to notice an extra 1-2 hp from super-wizbang sparkplugs when they seldom see full throttle or more than 5000rpm on their tachometer?
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Old 12-01-2012, 08:55 PM   #28
jackd
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Quote:
Originally Posted by robtg View Post
How many airhead riders are going to notice an extra 1-2 hp from super-wizbang sparkplugs when they seldom see full throttle or more than 5000rpm on their tachometer?
Well who knows? Maybe that extra 1 - 2 horsepower will make me slide further back on my seat when I open her up...
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Old 12-01-2012, 09:12 PM   #29
robtg
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Originally Posted by jackd View Post
Well who knows? Maybe that extra 1 - 2 horsepower will make me slide further back on my seat when I open her up...

Only if you are wearing Levi's and you Armoralled your seat.
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Old 12-01-2012, 09:34 PM   #30
jackd
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Well there's one thing I did learn in this thread and that is I'm running the wrong plugs in my bike. For some reason I bought BP8ES plugs last time out and I should be running BP6ES - slight oversight on my part. Shows you how much I'm paying attention these days. The funny thing is that I swore she runs better than she used to.. Maybe I'm getting an extra couple of horsepower out of these things.
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