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Spark Plug Question...totally bizarre

  • Thread starter Thread starter Chuckster
  • Start date Start date
C

Chuckster

Guest
I have a 1981 Suzuki GS550T with less than 9000 miles. Last night, I went to change the spark plugs. I pulled all four plugs out which were NGK B7ES. When I went to replace them, the base (threaded part) on the plug on the far left (while sitting on the bike) is much larger than the other three. You can notice the difference just looking at the spark plug hole compared to the next one. All four plugs are NGK B7ES, even the one with the larger threaded base. Anybody know what the heck is up with this? I've never seen it before. The dealer also gave me NGK B8ES to replace them with which all have the same size threaded portion.
 
Chuckster said:
I have a 1981 Suzuki GS550T with less than 9000 miles. Last night, I went to change the spark plugs. I pulled all four plugs out which were NGK B7ES. When I went to replace them, the base (threaded part) on the plug on the far left (while sitting on the bike) is much larger than the other three. You can notice the difference just looking at the spark plug hole compared to the next one. All four plugs are NGK B7ES, even the one with the larger threaded base. Anybody know what the heck is up with this? I've never seen it before. The dealer also gave me NGK B8ES to replace them with which all have the same size threaded portion.
Click to expand...


Hi there Chuck. If you indeed REMOVED 4 B7ES plugs, they were the same size.

If you actually have one hole thats now larger there's a couple of possibilities. First is that you pulled all the aluminum threads (cored out) this one hole and that aluminum thread material is on the one plug. Second (probably more likely) is that this happened in the past and that there was a Helicoil (or similar) thread insert which now has come out with that one plug (check to see if one plug appears to have a odd looking larger thread wound around it's original thread).

If the latter seems to be the case, all "might" not be lost, a properly installed similar type thread insert or one of the other types of replacement "threadsert" type repairs could be still done - at this point you might want to have an experienced engine builder (small, motorcycle or otherwise) do the work. Many times it can be done with the head installed although it's nicer with the head off.

If you're not talking about the actual plug thread hole but merely the base of a plug, I've seen production differences between old stock and new which can make one plug of the same number appear quite different but on close examination the threads, reach, protrustion will be the same even if overall height is slightly different. Hope this helps :)
 
It sounds like the spark plug threads in the head may have been repaired with a thread insert or helicoil. Sometimes this insert comes out with the plug instead of staying in the head.

You might be able to replace the insert if you can figure out exactly which brand it is, or maybe if you're extremely careful you can remove the old insert from the old plug and put it back with some high-temp locking fluid.
 
Spark Plug Question.....bizarre.....prevention

Spark Plug Question.....bizarre.....prevention

Just a note to add Chuck regarding prevention of such a problem (initially).
Never remove spark plugs from a hot ALUMINUM head .....Reason is that immediately after shut-down the aluminum cools quicker than the steel, seizing tightly around the steel plug until all temps are stabilized (cool).

Best cold and never force a plug out or in!
 
Thanks for the information guys. I just looked at the plug again and it does appear there is an outer threaded piece over the original plug. The threads on it are fine as well as the threads in my engine. I hope they are fine in my engine as they appear to be. I actually found out I had a problem when I attempted to screw my compression tester into the hole and it kinda went down easy and had some play in it. So then, I was wondering what the heck had happened, etc. I looked at the hole threads and they appear to be okay. I don't think the tester fit tight enough when I put in down in there to mess the existing threads up. I thought it was threading since it went in so easy until I realized it wasn't tightening up. Is there any way to get the one off the plug I have? Also, where would I get a replacement if I went that route? And finally, how can you secure it next time so it doesn't come out with the plug? By the way, the engine was cold when I did this last night. I've only had the bike several months so this was my first attempt to change the plugs.
 
You can check at your favorite auto parts store or a good bike supply to see if they have Heli-Coil kits for re-threading spark plug holes. Most of these kits have a tang on the bottom of the coils that you need to break off, which is not something you want to do unless you can be assured that you will not drop that little piece into the cylinder. Best bet would be to take the head off, but there might be a way to avoid that.


.
 
Steve said:
You can check at your favorite auto parts store or a good bike supply to see if they have Heli-Coil kits for re-threading spark plug holes. Most of these kits have a tang on the bottom of the coils that you need to break off, which is not something you want to do unless you can be assured that you will not drop that little piece into the cylinder. Best bet would be to take the head off, but there might be a way to avoid that.


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Click to expand...

Thanks Steve. Nothings easy is it? All I wanted to do was replace the plugs. It started out simple enough.
 
I pulled a heli-coil out of a cam cap bolt. I screwed the heli coil off the bolt a couple of turns and reinserted it into the threads with some heli coil locking compound. I then pulled the bolt out of the threads without removing the heli-coil with it. I let it set up and it held fine.
Just be careful not to break the heli-coil.
Or just get some new heli-coil threads.
 
chef1366 said:
I pulled a heli-coil out of a cam cap bolt. I screwed the heli coil off the bolt a couple of turns and reinserted it into the threads with some heli coil locking compound. I then pulled the bolt out of the threads without removing the heli-coil with it. I let it set up and it held fine.
Just be careful not to break the heli-coil.
Or just get some new heli-coil threads.
Click to expand...

Chef, how did you get the heli coil off the bolt without damaging it? Mine appears to be on my spark plug pretty tight.

Also, how do I figure out what size heli-coil is on it now if I can't get the other one off?
 
Size one of the spark plugs that are fine.
or
Someone here knows the size.
I don't.
 
chef1366 said:
Size one of the spark plugs that are fine.
or
Someone here knows the size.
I don't.
Click to expand...

Was the heli-coil already loose on the bolt you mentioned? I was wondering how you got yours off as mine is really on there pretty good.
 
Mine came right off. Yours is probably glued together so maybe try some penetrating oil or just get a new one. The hard part of the job is done which is retapping the threads. All you have to do is thread in some new ones.
 
chef1366 said:
Mine came right off. Yours is probably glued together so maybe try some penetrating oil or just get a new one. The hard part of the job is done which is retapping the threads. All you have to do is thread in some new ones.
Click to expand...

Thanks. Good idea. I'll try some PB Blaster tonight and see if that loosens it up.
 
A tip to remove the coils...

grab them loosely at the TOP of the coils and turn. This will help expand them a bit and loosen their grip on the plug. If you grab near the bottom, it constricts the coils, tightening their grip.

That is why there is a drive tang on a new coil. That way, you are pulling it into the threads, then letting it expand into place. On the bolt (plug, in your case), you want to expand the coils to remove them.


.
 
The "B" in NGK B8ES spark plugs denotes a 14mm thread diameter, which will have to be the interior diameter of a replacement threaded insert (Helicoil or other type).

The "E" denotes a 19mm (3/4") thread length.
 
If that is the same insert I had on a previous bike there is a way to remove it from the plug. Go to your local automotive supply store and buy a 5/8" fine nut, (I think that was the size, maybe measure yours) You'll have to cut the nut across one of the flats so you can expand it slightly to be able to thread it onto the insert. Clamp the nut in a vise and remove the plug from the insert, then take out of the vise and remove the insert from the nut. Reuse the insert on the new plug and throw the nut in your toolkit for future use. Sounds like a bit of a PITA but it does work and is a lot easier than replacing the head. These inserts are not pinned in place and can come out with the plug. Any attempts to pin it in place will most likely only further damage the head. I imagine once the head has been drilled and tapped for this insert that removes any possibility of properly installing the heli coil kit which probably should have been done in the first place. Hope this helps, good luck.
 
Thanks for all the tips guys. I really appreciate it.

You're not going to believe what happened last night. When I got home yesterday evening, I put the three new plugs in as well as the old plug with the heli-coil on it. I tightened all four down to 14.5 ft pds of torque with my torque wrench. I really just wanted to see if the old one with the coil on it would still tighten down. I didn't think anything else about it. Well, I feel asleep and work up about 11:30pm and remembered that a friend was going to bring in his heli kit to work so I went down to remove the plug to carry in to work. I broke it loose with my ratchet and took it out. I was still half asleep, but it looked like my other plugs. I thought this could not be! Yep, it left the heli-coil in there when I removed the plug! I guess when I got home, I was twisting the heli on the plug with a rag trying to get it off and also wiped out the plug hole. This must have cleaned them up enough combined with the torque when I put it back in to keep it in when I removed it. I couldn't believe it.

I haven't put the new plug in yet. I wanted to know if there is something I can put on the plug threads so I won't "bind" to the heli-coil again? Is there such a thing? I wish I had put a drop or two of red locktite on the heli before I put the plug back in, but I was scared it might seep through and bond my plug in there with it. Hopefully, it will stay in there now.
 
You could try using a bit of "Never-Seize".

It should be used, anyway, any time you have steel meeting aluminum that you hope to remove some tmie in the future. 8-[


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