A tale of 3 spark plugs

3585 Views 21 Replies 12 Participants Last post by Rolex, 4 mo ago

bajakirch

Discussion Starter · 4 mo ago (Edited)

Today I set aside some time to replace the spark plugs on my 2012 DL650.

Currently, I have NGK CR8E's installed.

I planned to replace them with E3.38 'DiamondFIRE', which alleges to be swappable with the NGK CR8E. Except, when I pulled the first plug and put in the E3, the cap wouldn't go on. On inspection, it appeared the top of the plug was significantly wider than the NGK.

No problem, I have a couple of auto parts stores nearby. I was able to buy 4 Autolite 4303's, which their system said is compatible with my bike. But when I came home, I found the exact same problem with those -- the top is too thick.

I tried for a while to see if the plugs with the thicker top would still work, but I can't get the cap to seat properly.

Am I doing something wrong here? I've replaced my plugs several times before and never recall having this problem.

Here's a comparison photo for illustration:

Edited to add: My manual specifies NGK CR8E-IA9 for my bike. I did a quick Amazon search using that exact term and I get returns that show both the thicker and thinner tops. What gives?

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STCorndog

· #2 · 4 mo ago

It’s hard for me to tell. But the threaded portion of the two plugs on the right looks slightly longer than the left plug.

Time is money. I buy motorcycle parts from the dealer or online and use only OEM.

This is why.

PS- the contact caps will unscrew from the top of the plugs.

Reactions: 4

TinMan88

· #3 · 4 mo ago

online.flippingbook.com

NGK Automotive Spark Plug Catalog v1.0

This interactive flipbook is created with FlippingBook, a service for streaming PDFs online. No download, no waiting. Open and start reading right away!

online.flippingbook.com

All the nomenclature is there. Some times it is best not to outguess the spec.

Did you remove the large lug at the top?

Reactions: 1

BackPacker

· #4 · 4 mo ago

STCorndog said:
PS- the contact caps will unscrew from the top of the plugs.

This!

Been caught by this multiple times.

Reactions: 2

bajakirch

Discussion Starter · #5 · 4 mo ago

So, what it sounds like is that the larger-diameter lug from the original plug has unscrewed and is stuck in the plug cap.

I took a few shots at screwing the old plug back into it and pulling it out, but so far I'm unsuccessful. I also tried reaching a small needle-nose pliers in there and tugging it out; also a no-go.

Any other suggestions?

Rolex

· #6 · 4 mo ago

If we are talking about just the cap not fitting the tip of the new plugs should unscrew to reveal a thread just like the original plug.

Many plug models used on cars don't have removable caps/tips but if the plug is made for a bike is should have a removeable tip.

If you look in the cap for a bike there will be a type of sideways clip, looks like part of a figure 8, it will catch on the threads on the top of the original plug

If you look in the lead for a car they have a socket type fitting suited to your new plugs

Reactions: 1

jettawreck

· #7 · 4 mo ago (Edited)

The top terminal that unscrews is stuck inside the plug cap. It used to be a common occurrence on old snowmobiles (vibration monsters).
Often the internal terminal of the plug cap will unthread (some types have an internal 5k resistor, so make sure that doesn't fall out and disappear), or if you are fortunate you can get the old plug's threaded terminal to engage the threads and remove the threaded on terminal, but often from being loose for some time all the threads from the aluminum plug terminal have worn away.
But regardless, I wouldn't use either/any "alternative" sparkplug crossovers. NGK were designed to be used and they are the best anyways. The local Fleet Farm carries a huge NGK (and a couple other brands) selection and very reasonable prices.

Reactions: 1

TinMan88

· #8 · 4 mo ago

bajakirch said:
Any other suggestions?

Take it a shop?

Many small engines use the threaded post to retain the cap.

Brockie

· #9 · 4 mo ago

I cannot remember if the threaded top of the plug should be on or off. If in doubt remove another of your plugs to see.
Perhaps an optical thing but I also wonder if your new plugs are a deeper reach than the NGK.

Reactions: 1

BackPacker

· #10 · 4 mo ago

bajakirch said:
So, what it sounds like is that the larger-diameter lug from the original plug has unscrewed and is stuck in the plug cap.

Correct me if I'm wrong, but I've always worked under the assumption that the lug should simply not be there, as the spark plug lead is supposed to grab the threads of the smaller-diameter post. So I have, so far, always removed the lug (after a period of puzzlement, like you) and push the spark plug lead onto it.

Reactions: 1

hillsy

· #11 · 4 mo ago

There's no way the screw tip of the plug has unscrewed itself inside the plug cap.

By all means double check with the other plug cap, but the plug should have just the threaded tip, not the screw on tip.

Reactions: 1

Marmora

· #12 · 4 mo ago

hillsy said:
There's no way the screw tip of the plug has unscrewed itself inside the plug cap.

By all means double check with the other plug cap, but the plug should have just the threaded tip, not the screw on tip.

As said above.Others tried to say it,but you put in words simply as l struggled to.
Also don’t CHIMP OUT on parts.Buy iridium.NGK…

jettawreck

· #13 · 4 mo ago

hillsy said:
There's no way the screw tip of the plug has unscrewed itself inside the plug cap.

By all means double check with the other plug cap, but the plug should have just the threaded tip, not the screw on tip.

Seen it many times on ATVs and snowmobiles where the tip was/became loose and after time vibration takes all the threads out of the tip and while it doesn't really "unthread" by turning, the threads are gone and when you pull the cap it strips off the plug and remains in the cap.
The alternate spark plugs look like slightly longer reach threads to me also.

Reactions: 3

stickerbush

· #14 · 4 mo ago

Looks to me the reach on the threads is the same on all 3 plugs.

Tire Font Auto part Office supplies Circle

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STCorndog

· #15 · 4 mo ago

stickerbush said:
Looks to me the reach on the threads is the same on all 3 plugs.

View attachment 312152

Well aren’t you slick, and I agree visually. When I change plug brands, I take a new one and an old one and mesh the threaded portions together. Quick way to check thread pitch and length.

Reactions: 5

hillsy

· #16 · 4 mo ago

I'm trying to think of a bike that uses spark plugs with the thread caps on? I think it's a car thing.

blaustrom

· #17 · 4 mo ago (Edited)

Boy o Boy. Just unscrew the fat adapter part from the top and move on with life. Most spark plugs have this adapter since some caps require it. Just look, there is nothing stuck in your caps.

And then why are you replacing the old plugs, just re-gap them ....

Greywolf, may he rest in peace, for reference:

https://www.v-strom.co.uk/smf/index.php?PHPSESSID=e55d25a0ed7140eb672ad730151021ee&topic=27058.msg269278#msg269278

From another Trooper (Should I Replace Spark Plugs at 7,500 Miles):

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dwfree

· #18 · 4 mo ago

Some spark plug caps require the screw on lug, some do not, both cars and bikes. No way will a plug with the lug fit into one that requires the threaded tip. Several decades ago the plug lug would sometimes be loose (maybe a turn), but never vibrate out. Over the last 30 years or so, with much improved plug caps, I've never had one loosen up.

Easy check is to remove all plug caps. If all are threaded tip there's your answer. Most likely a threaded tip cap. If the electrodes are still square no need to replace, check the gap and reinstall. Iridium plugs are great for really extended mileage - got a set in a cage with 150k mi - but no other performance improvement (do not gap check iridium plug per mfrs).

bajakirch

Discussion Starter · #19 · 4 mo ago

I feel a bit silly now knowing I can simply take off the lug at the top. It's weird to me that, having swapped plugs many times before on this and other bikes, that I've never encountered this before.

As an addendum, I tried taking the lug off the top of one of the E3 plugs and it won't budge. I even tried gripping it with a small pliers. But the top on the Autolite plug easily screwed off.

hillsy

· #20 · 4 mo ago

bajakirch said:
As an addendum, I tried taking the lug off the top of one of the E3 plugs and it won't budge. I even tried gripping it with a small pliers. But the top on the Autolite plug easily screwed off.

Some plugs have top lug non removable. There's a number or letter in the plug code that designates this but I can't recall which.

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