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The Fear Of Tightening Spark Plugs

Blog Date - 12 January 2019

I've just checked the tappets/rockers/valves/shims on the CB500X. Oh my word it's a faff, a lot of messing around, a pain in the derrière. That said as this is my third time doing this I must admit it has become a lot easier. While I'm down there I might as well fit some fresh spark plugs.

But, there's always a but.

I am a worrier. It's the way I'm made or perhaps I have some deep rooted issues caused by a childhood trauma. Maybe it was that time I stood on some Lego when going to the loo in the middle of the night. Maybe it's because I wasn't born into a wealthy family like I was supposed to be. I do like to worry.

It has taken me a long time to stop tightening every nut, bolt and screw up as tight as I can... just in case it rattles loose as I'm riding along causing myself serious injury and the death of a coachload of future geniuses on a school bus, one of whom was destined to cure cancer and another who was going to crack room temperature fusion.

Of course the downside of these super-tight nuts, bolts and screws is it wasn't uncommon for me to thread them. So I soon developed a fear of over-tightening fastenings to match my fear of killing the world's future.

Retapping the threads in a cylinder head
Oh joy. Joyous joy. I feel queesy just seeing this image.

The correct tightness is tight enough to not come loose, not too tight to risk stripping out the threads. There are in fact things called "torque wrenches" but there's an twist (HA! Gerrit!!) to these. They're big. They're good for big nuts like the ones holding the wheels on the bike. My big torque wrench goes down to 10 foot pounds but at that level it's about as accurate as a politician's predictions.

And guess what sort of threaded things tend to strip their threads? LITTLE nuts and bolts, that's what. Things that only need 4, 5 or 10 feet pounds. I have seen small torque wrenches which I presume are more accurate at these lower settings? Maybe I should buy one. Most good manuals will have most torque settings and there are charts for various metals, threads, lengths and so on. Seriously nerdy stuff.

A small short torque wrench
Dinky torque wrenches for dinky nuts and bolts.

Anyhow. But. As explained I have a fear of tightening things. Especially spark plugs. A threaded engine case, meh, there's plenty of others we can live without that one. A threaded wheel spindle, pain in the ass but just buy a new one and slide it in. A threaded spark plug hole? That's a whole world of pain removing the cylinder head and either replacing it or getting it helicoiled.

Due to my fear of (almost) everything I am fitting Iridium plugs. Why? Because of their improved spark? Because of some technical things that I don't understand? Nope. Because they last a long time so they don't need replacing that often so I don't have to go through the worrying about the how tight they are thing too often. I'm not just a pretty face you know.

NGK understand my fear. As such they've kindly given me a tiny little diagram on the side of the box. Put the plug in hand tight then using a wrench tighten it by about 1/6th of a turn. Wait what? I'm sure it used to be a quarter turn but this diagram clearly shows LESS than a quarter turn. Things change. If NGK said insert till hand tight then secure with the bogeys of a small child then that is what I should do. I'd have to get someone else to get the bogeys because I hate small children. And big ones too.

The guide on the box from the spark plug
Tighten by hand. Turn 1/6th of a turn. Not a quarter any more, one sixth. One section of a six sided nut.

The nice picture shows hand tightening using your hand. Hmmmm. My spark plug's hole is located down at the bottom of a 3 metre well that requires 4 sockets extensions and a drilling rig to reach. I can't get my hand in there. OK, yes I know. I tighten the plug as much as I can by turning the extensions with my feeble fingers.

The rocker cover has 2 deep holes donw which are the spark plugs
Deep deep down in them there holes are the plugs.

I fit my ratchet wrench. I carefully note it's position and calculate a 1/6th turn. I turn the ratchet wrench. It does not feel enough. At all. My every being screams at me to go at it harder, make it tight, make sure it doesn't work it's way out! I give it another couple of degrees but then stop. No. no no no. NGK know what they're doing. There's a crush washer designed to work like this. I stop, unwillingly but I stop.

The bike is running fine. I'm sure in the fullness of time I will stop worrying that the spark plug will work its way loose then shoot out the top of the engine then enter the fuel tank which will blow up and leave me scarred for life with terrible burns and a girl that witnesses this will suffer from post traumatic stress disorder and never find the answer to interstellar travel that solves world hunger.

Seriously though. I do worry, maybe not as much as I've made out here but I do worry. Like the tightness of a threaded fastener there is a healthy balance of worrying to be found. If I was "laissez faire" about tightening things I'd be at risk of things falling off. I also and I should worry a little about my trips because some preparation is always required. Equally - worrying too much can spoil the fun of a trip and paralyse the pleasure I get from spannering and tinkering.

I am getting better at finding the balances of my tightening, my trip preparations and my worrying. It's far from perfect and I don't believe it ever will be, but better is better so I'm happy with that.

If you're business sells small torque wrenches and would like to sponsor Bikes And Travels with one we'll do a review on it and mention your name! Contact

Reader's Comments

NigelS said :-
Sorry, but I'm a great believer in doing things properly and there really is no substitute for the proper tools. £35 will buy you a 3/8 drive 5-50 lbs ft torque wrench (Silverline, Nielsen, Sealey etc) which will be accurate for tightening not just spark plugs but all small (4mm) fasteners viz oil filter, engine outer covers etc. I have to be especially careful on a Chinese bike as the castings are probably not nearly as good as your Honda. I'm sure others will poo-poo the thought of spending such a huge sum of money for the right tool but I like to sleep soundly without worrying that I might have over/under tightened it and will it fall off or strip the threads!
12/1/2019 4:08:35 PM UTC
Upt'North said :-
You are a worrier, our Ed. If in doubt a torque wrench is best and you'll be using it for the next 30 or 40 years. My man maths says about a squid a year. That's the upside.
I can remember one acquaintance who fitted new spark plugs to his Ford Capri, it was a while back. Whilst taking it out for a spin later one decided it wasn't quite tight enough and formed a power bulge in the bonnet as it tried to escape. He wasn't chuffed. Don't worry Ed yours will just go into your tank, dropping the fuel all over the hot exhaust and cabooommmmm.
Hope that settles your mind a little.
12/1/2019 4:22:37 PM UTC
Ren - The Ed said :-
I...I fear this...I'm happy to spend a few quid on a half decent small torque wrench. I'm thinking for dinky nuts and bolts more like a 1/4 inch drive. My half inch one is fine for the big stuff, it's mostly used on wheel nuts and engine mounting bolts. That said it's like 25 years old at least now, I wonder if they lose their accuracy?

Draper has a 1/4 inch drive 5-25nm (3.6 to 18.4 ft-lbs) for £25. Hmmmmmm.
12/1/2019 5:06:15 PM UTC
Ren - The Ed said :-
Oh and Upt'North. Go and do something horrible to yourself you rotten meanie.
12/1/2019 5:07:13 PM UTC
Upt'North said :-
Rotten Meanie.....there's no need for that kind of language, young man.
Torque wrenches if looked after will last a long while and still be accurate. But if you are the type to throw your tool about (oooohhhh matron) then they won't. I'm sure you do this Ed, but just in case always wind the load off before storing it away.
I've never tried to self calibrate a torque wrenc, but I can see no reason why you couldn't hang a known weight off a known length lever, ie, 20 lbs on a 1 foot lever and check your wrench against that. If the nut is the same tightness all shod be good. No?

12/1/2019 6:01:26 PM UTC
Jim said :-
As others have said, no substitute for the right tool, and £25 is a bargain. However, you're unlikely to cause any damage by slightly overtightening a spark plug that has a washer. On the other hand, I once had to drill four conical seat spark plugs from the head BL 'O' series engine after they had been only very slightly over-tightened. Ended up having to get Helicoil inserts. But don't let that put you off, Ren (unless you've got a 1979 Morris Marina stashed away somewhere).
12/1/2019 6:32:29 PM UTC
pocketpete said :-
Don't worry about the small torque wrench I will get you one for you when you do my shim things along with a breakfast.

I had exactly the same problem whenn doing up the brake bolts after I changed my pads I my own only went down to 30mn and I need to go to 12 or 17.
12/1/2019 6:34:38 PM UTC
Ren - The Ed said :-
Sorry Up't'North, such terrible language. Sharon says she's going to wash my mouth out with coal tar soap.

I was taught as a young spanner monkey to ALWAYS slacken off the torque wrench before putting it away. This stops the spring from shortening due to being under constant load. I always have done and I have instructed Sharon to do the same with hers.

Checking would be easy. For ideal accuracy using a bar and weight would not be 100% accurate. Why? Because of the weight of the bar! Of course a light tube and say a 20 pound weight checked against the torque wrench would be MORE than accurate enough for our purposes.

No Jim there's no substitute for the right tool. Sharon often thinks I'm a right tool and wishes she could substitute me for a nice man. Apparently she painted a wall in the living room from white to green. I did not notice.

Cheers Pocketpete. I'll message you on faceache and arrange a suitable day or two.
12/1/2019 6:57:18 PM UTC
pocketpete said :-
Maybe your suffering from a phobia of some sort cant seem to find one to exactly match your fear of tight spark plugs.
nothing quite matches.


SpendSpannerphobia: Fear of spending money on Spanners
RenTightenPhobia: Fear of Over doing your nuts or maybe just tight
Chrometophobia: fear of mmoney

Motorphobia: The fear of automobiles in general, also referred to as ochophobia. This goes as far as fearing the very idea of vehicles, much less being around them.
Mechanophobia: The fear of machines. For some, anxiety about vehicles can extend further to most man-made, mechanized creations.
Claustrophobia: The fear of closed, small spaces. Automobiles might look harmless from the outside, but being stuck inside the confined, enclosed cabin of a car can cause intense panic.
Vehophobia: The fear of driving. Being in vehicles might not be terrifying, but controlling one can cause severe emotional distress to some.
Amaxophobia: The fear of riding in a car. Even if you're not the one behind the wheel, riding in a car can create a paralyzing sense of dread for some.
Dystychiphobia: The fear of accidents. A reason some people don't like being in a moving car, this phobia is concerned with the possible danger on the road.
Traumatophobia: The fear of injury. Related to fearing vehicular accidents, you can fear any sort of bodily harm, inside or outside the car.
Hodophobia: The fear of road travel. Some people avoid travelling on the road altogether due to this.
Technophobia: The fear of advanced technology or complex devices. As vehicles continue to get more computerized and digitally-connected, this phobia is affecting more drivers.
12/1/2019 9:36:20 PM UTC
Steve said :-
I'm not a great fan of changing spark plugs on these deep recessed heads either. Pushing the plug down on a long box spanner extension always gives me fear of cross threading as well. Fortunately on the NC700 they only need changing every 32k so I've only had to do it once and have a couple of years to build up for the next one and if the stress gets too much i can sell the bike before 64k.
13/1/2019 9:13:01 AM UTC
Ian Soady said :-
I do have a couple of torque wrenches but rarely use them (definitely not for plugs) and I can't remember the last time I stripped a thread. The recommendation from NGK seems reasonable but only applies to the first time you fit them as the washer has crushed then so on subsequent fitting will need slightly less torque to be applied. Mind you, plugs are so cheap these days that many people will never actually refit them.

The worst thing is just to leave them in there for too long as the danger is they corrode in place as Jim experienced on the O series. For most people (not Ren or Sharon of course) 32K miles would be several years giving plenty of opportunity for them to seize up.

WRT the deeply recessed ones I have a 3/8" drive socket with a rubber insert that holds the plug quite tightly and in line so it's relatively easy to start (using finger pressure only of course). But I accept some are harder to get at than others.
13/1/2019 12:20:22 PM UTC
Steve said :-
Good advice there Ian, my NC has done over 50k and I have had the plugs out a few times just to check. Because the engine lays over almost flat the plug recess is quite protected from water and when the belly pan is off access is good.
The 32k inteval translates to about 3 years for me but in practice they get looked at least bi annually and refitted with a wee smear of copper lube on the threads. As you say those rubber insert deep sockets make the job of centering and starting the thread alot easier.
13/1/2019 9:06:31 PM UTC
Ren - The Ed said :-
Despite a perhaps rather sensible fear of recessed spark plugs there are advantages to them. As Ian noted spark plugs rust. The plug on the CBF125 sails out in the wind and soon changes from a shiny metal finish to a crispy crusty rust patina. It is - I believe - the reason I've had trouble with the spark plug caps as they're so exposed. However the plugs pulled from the deeply recessed 500 have lost their shine for sure but they're not rusty and have a mere light dusting of dirt upon them.

Pros and cons as always.
14/1/2019 8:10:59 AM UTC
Ren - The Ed said :-
Excuse me folks...I'm just testing the updates are working...

14/1/2019 7:55:19 PM UTC
Snod said :-
I use my cheapo small torque wrench for cam caps, some of these can be very sensitive to torque as overtightening them can warp the cap and promote massive wear. I've never used it for plugs though, I just turn the socket as much as the box says.

Best of luck with the iridium plugs btw, I ran a couple of Denso iridium plugs and they were absolutely fantastic for the first 50 miles or so, then the same as the old NGK coppers, then they died after 6K miles with the spark crawling down the outside of the porcelain. The boring NGKs did 25K!
14/1/2019 9:32:25 PM UTC
Ren - The Ed said :-
I've used NGK Iridium in the Fazer 600 before now with no issues. I guess there's baduns in every bunch. Like ya say there's an element of luck. Managed over 100 miles this weekend without issue... I just hope there's another 50,000 miles more to go!
14/1/2019 9:47:15 PM UTC
Snod said :-
Absolutely, the plug that comes in a 250SL is a special iridium with a platinum core which seems much more resilient - 13K for me and not a spot of bother. Considering they're about £14 each it can stay there for as long as possible!
14/1/2019 10:05:05 PM UTC
Ross said :-
"Ren - The Ed said :-
Excuse me folks...I'm just testing the updates are working..."

Something doesn't look right to me...!

15/1/2019 8:30:17 AM UTC
Ian Soady said :-
I quite like it. A change from those boring photos of motorbikes......
15/1/2019 9:52:22 AM UTC
Upt'North said :-
Ross, I think you're being a little over critical, it could be turkey deprivation. For you or Ed.
I personally think the man, that's if he is a man and not someone deposited here from a far flung galaxy, is a genius. Just look at those lovely bright coloured ?. How does he do it. I can only watch and wonder. He's certainly wasted here, we don't deserve him, no we really don't deserve him.
I believe he could be head hunted at any moment, just his head, nothing else. I look forward to the I.T.weekends at Ed Towers where we can all be facilitated upon from a great height. While we've still got you Ed, thank you from the bottom......
Yours sincerely,
15/1/2019 10:56:59 AM UTC
Ren - The Ed said :-
Yes yes yes you're all a bunch of sarrrrrrcarrrrstic swines.

If only you knew what great technological feats of genius and cunning guile it takes to make this website work on a technical level. At least Upt'North appreciates my intellect is in fact "other worldly".

There are still a couple of wrinkles to iron out. These are deliberate. When one is blessed with such superior wisdom one must understand that the lessers I mingle with may feel terribly inferior around me. So I sprinkle in a few minor errors to ensure they don't feel overwhelmed by my presence. As regards my artistic digital prowess, might I lead you all to the power of "print screen" and Microsoft's "Paint".
15/1/2019 11:41:35 AM UTC
Ian Soady said :-
Talking about plugs - this was the one that came out of the Norton. It's obviously given good service and the bike was running quite well with it installed.

Note how thin the earth electrode has become....
16/1/2019 12:15:14 PM UTC
Ian Soady said :-
Talking about plugs - this was the one that came out of the Norton. It's obviously given good service and the bike was running quite well with it installed.

Note how thin the earth electrode has become....
16/1/2019 12:15:14 PM UTC
Ian Soady said :-
Where's my photo?

Ah here it is. Improvements? If it ain't broke fix it till it is seems to be young Ren's motto.

16/1/2019 12:16:35 PM UTC
Ren - The Ed said :-
There are good reasons for the update. I could get all technical on you but then you'd just disagree. You'll be fine when you get the hang of it.
16/1/2019 2:06:51 PM UTC
GraemeC said :-
Hi Ren. Another spark plug fear I have, especially with plugs which are set in a deep recess,is the possibility of a piece of grit or other crap dropping into the cylinder when you remove the plug. In addition, when installing a new plug there is an opportunity to dislodge crap at the bottom of the hole when you are fiddling around trying to get the thread started which then falls into the engine. Can you imagine the damage being caused by that grit? I found this "fear" overrides the "tightening" fear, and is actually worse. Just another thing to worry about :)

Don't have nightmares :)
17/1/2019 10:09:41 AM UTC
Ren - The Ed said :-
In an ideal world GraemeC I'd have a long thin artist's paint brush and an airline. I'd use the paintbrush to loosen the grit and dirt then the airline to blow it out.

I did have a suitable skinny paintbrush. I don't have an airline. I ended up fixing a thin straw from a WD40 tin to a bicycle pump. A couple of sharp firm pumps down each recess was sufficient...this time.

I really do need some compressed air. BUT I don't require it often at all. As such I'm thinking of making something I can pump up with a regular foot pump that holds enough air to blow out dirt from recesses and to seat the bead of of a tyre. Hmmmm....
17/1/2019 11:11:23 AM UTC
GraemeC said :-
Good point - clean the hole before starting. Have you tried those tins of compressed air (used for cleaning IT components)? Maybe not enough pressure, but they do have a straw to direct the blast. Might work....
17/1/2019 11:20:35 AM UTC
Ian Soady said :-
Suck is better than blow.....

Tape some small diameter tube to the nozzle of a vacuum cleaner (yes Ren I know you don't have one but Sharon will lend you hers) and use that to suck any bits up before you remove the old plug then again once it is removed. Blowing always has the possibility it will send bits where you don't want them.
17/1/2019 12:29:33 PM UTC
Ren - The Ed said :-
GraemeC - I very nearly bought one then I remembered I'm tighter than a ship's rivets. I have a cunning plan...

Ian Soady - I know what you mean - but. If everything is buttoned down ie. the rocker cover is still on then the rest of the engine catches light dirt all he time. I'm not quite sure "suck" would suck with the same force as "blow". Worth considering though. And yes I do have a vacuum cleaner. Somewhere.
17/1/2019 6:25:53 PM UTC

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