Iridium spark plugs ST1300

[ST1]

I am changing the spark plugs on my 2008 St 1300, The plugs I have taken out are CR7EH and the ones I an putting in are CR7EUX
Ther is a blank part on the thread on the plug taken out this detail isn't on the Iridium plug. Will this be an issue?

 

[SMSW]

The CR7EH9 is what NGK recommends on their website. If you go to the codes, C = thread, 10mm x 5/8"; R= resistor; 7 = heat range EH = Reach, 19mm half thread; 9 = gap. Your left plug in the pic seems to show CR7EIX and the E = 19mm reach, the IX = fine wire iridium. I assume your CR7EUX.

It should make no difference, since the sealing washer is in the same position and the old plug screwed into the head fully (the unthreaded portion went in until the washer seated). Guys with more experience than I w/ iridium plugs will weigh in.

Be advised that there are a LOT of counterfeit spark plugs floating around, especially expensive iridium versions. There have been posts of websites that describe the differences between the printing and stamping of fake plugs. Do a search and make sure you have the real thing.

 

[ST1]

Yes CR7EIX so the iridium plug has to be gapd the same as the original plug.

 

[Valker]

That non-threaded part is supposedly a requirement on the ST spark plugs, to prevent contact between the piston and the plug. I will only use the plugs with that non-threaded portion.

 

[Andrew Shadow]

The location of the sealing surface and thickness of the washer along with how far the plug protrudes after that point, regardless of whether it is threaded or not, is what determines how far in to the cylinder a spark plug will reach. If the location of the sealing surface, washer, and the length after that point are all the same on both of these plugs they will both extend in to the cylinder by the same amount.

 

[dwalby]

That non-threaded part is supposedly a requirement on the ST spark plugs, to prevent contact between the piston and the plug. I will only use the plugs with that non-threaded portion.

I don't ride a 1300, so just interested in general, but isn't the crush washer at the top what ultimately stops the plug from threading any further into the hole? If so, then both plugs would extend the same distance into the cylinder.

edit: Andrew beat me to it by about 5 seconds.

 

[Willsmotorcycle]

That non-threaded part is supposedly a requirement on the ST spark plugs, to prevent contact between the piston and the plug. I will only use the plugs with that non-threaded portion.

Genuine question how would that work?

Aren’t the distances from the shoulder to the electrode the same?

 

[ST Gui]

Genuine question how would that work?

It wouldn't. As mentioned the crush washer is the sealing surface. The unthreaded portion isn't a shoulder for the 1300 but maybe it is for some bikes. It's wider than the threaded portion so you might look at that and assume it limits the protrusion into the cylinder. I've never looked into the cylinder but I'm guessing the plug bore is relieved to accommodate the unthreaded bit.

The shoulders of both plugs being the same diameter means either one should fit and seal properly without trying to occupy the same space as the piston.

 

[SMSW]

Genuine question how would that work?
Aren’t the distances from the shoulder to the electrode the same?

The EH part of the plug number is the reach - how long the plug is from the crush washer on. The non threaded part is the same OD as the ID of the cylinder head's threaded spark plug hole. The threads pull the plug, unthreaded part too, into the hole until the crush washer seats.

That non-threaded part is supposedly a requirement on the ST spark plugs, to prevent contact between the piston and the plug. I will only use the plugs with that non-threaded portion.

Not sure where that came from, since the "reach" of the plug is what determines how far into the cylinder the electrodes protrude. Since the specified reach is the same for both plugs, I'm not sure what you said is true. The EH plug is what NGK shows on their website for ST1300s.

How come there has been so little talk about counterfeit plugs here when there has been a LOT of it in previous threads>

 

[Valker]

All i know is the Honda Factory Service Manual references the unthreaded part as essential, so I use them.
I’m not even close to an engineer, I just ride the thing.

 

[Andrew Shadow]

How come there has been so little talk about counterfeit plugs here

Probably because

there has been a LOT of it in previous threads

To each his own of course but I really don't see enough benefit to even bother with iridium plugs. With all of the concerns that I keep reading about the uncertainty of whether it is the correct one, the correct heat range, if it is counterfeit or not, etc., it just isn't worth the bother to me. Added to that is that so many people replace their spark plugs at such short intervals that they don't benefit from the extended life that Iridium plugs are supposed to provide anyway. I also think that the claims of improved performance are grossly exaggerated for most of us. If you are racing an ST1300 it might give you an advantage. For most people riding on public roads I think that this benefit is questionable.

 

[Andrew Shadow]

All i know is the Honda Factory Service Manual references the unthreaded part as essential, so I use them.
I’m not even close to an engineer, I just ride the thing.

I try to find this in the service manual because I want to know what they wrote about this. I can't find any reference to this. Do you know where this is written in the service manual?

 

[ST Gui]

I used Ir plugs on most of my Hondas at the first plug change. I found they were easy to self-clean under hard acceleration at high RPM. Those were all carbureted bikes. I haven't had a plug change in the ST so I don't know if FI makes a difference but I've never seen any black exhaust being clear out of the ST. So i'm not considering changing to Ir.

 

[PanRider1300]

That are the wrong iridium plugs. You need that shoulder on the st1300 engine. You need the CR8EHIX-9

And you will feel no difference at all.
Only your wallet.

 

[dwalby]

That are the wrong iridium plugs. You need that shoulder on the st1300 engine. You need the CR8EHIX-9

And you will feel no difference at all.
Only your wallet.

I don't think the selling point of Iridium plugs has anything to do with performance, they are just a longer lasting plug because of the Iridium tips. They might cost 2x the price of regular plugs, but if they last 5x as many miles they're cheaper in the long run. Regarding the actual cost of either option, IDK the current prices because I put a set in my ST1100 so many years ago I can't even remember when it was and haven't priced spark plugs since.