12 Nm on the plugs? thats not very tight

on the plugs, they are more like a hollow steel 'O' ring that goes flat once crushed... I'm sure it needs to be fully crushed ??

I've never had a plug come out, but I've never done them to 12Nm before... I have stripped many threads however ;)
 
beaver said:
on the plugs, they are more like a hollow steel 'O' ring that goes flat once crushed... I'm sure it needs to be fully crushed ??

I've never had a plug come out, but I've never done them to 12Nm before... I have stripped many threads however ;)
Click to expand...

I've come across both types of washers, but what you say about steel washer sounds reasonable. In the "old days" with cast iron heads we used to screw until the sparkplug stopped at the washer, then 1/16 of a turn further (this has already been mentioned further back).

The tricky part about using torque wrench on sparkplugs when the engine have some miles on is that carbon buildup on the treads may influence the result. Personally I use copper grease on the sparkplugs to make them turn easy and prevent buildups on the treads. I know it may influence the torque, as there is no mentioning of grease in the service manual. (rule of thumb says 2-3 Nm deduction). This works out to allow the sparkplug to enter the washer, and the sparkplug more or less stops when the spring in the torque wrench starts to build up pressure. If you decide to use 15 Nm on dry plugs, I suspect that we more or less put the same strain on the threads.
I.e we are both ok, or we are both screwed :beerjug:
 
As the thread is hollow there isn't much metal, they haven't snapped so all is good,
the specified torque is on some engines so that the electrode faces in correct orientation ,like and not exclusive to some vw petrol engines, all to do with emissions,,,
 
Its a twin electrode plug so I'm not sure its orientated.... but do you realise how little 12 Nm is?... if you could get your hand on the plug and screw it in as tight as you could, you'd not be far off. :)
 
This is why I don't buy second hand bikes.

12NM on a new plug is fine, the second time you torque it to that the crush washer is already deformed so you're pulling on the threads, essentially deforming them to get the already deformed crush washer to seal. You go higher still and you are deforming the threads even more.

As an engineer I've been using torque wrenches for almost 40 years and never once had anything come loose because of it not being tight enough, had plenty problems with people over-tightening things though.

I hope it's ok for you.
 
Wobbly65 said:
This is why I don't buy second hand bikes.

12NM on a new plug is fine, the second time you torque it to that the crush washer is already deformed so you're pulling on the threads, essentially deforming them to get the already deformed crush washer to seal. You go higher still and you are deforming the threads even more.

As an engineer I've been using torque wrenches for almost 40 years and never once had anything come loose because of it not being tight enough, had plenty problems with people over-tightening things though.

I hope it's ok for you.
Click to expand...

As an Engineer myself, so have I, especialy in Aerospace... and yes, we all understand overloading a thread... but have you actualy read this thread before posting? I'm not on about the torque once crushed... I'm saying that 12 Nm does not crush it on the first go.... and whats the outcome of this?
Also you comment about second hand bikes LOL ... as said above. My bike has always been serviced by BMW and the ones I took out were way over the 12 Nm. the new ones are in at a lower torque for sure... so I'm not sure where you comment is aimed.. I guess your saying I'm a f*ckwhitt or something for raising this?.. well thanks for that.
 
I see. I thought you were looking for opinions not validation. My mistake.
 
Steptoe said:
Two pilot error = both crashed, hard impact. Tri-Pacer and EP9
One oil pressure lost, emergency landing in a field with body damage. Islander.
All in the UK

All my work was on twin beeches, Twin otter and DC3, in USA. :D
Click to expand...

They have more aeroplane crashes in the USA than the UK, is there a correlation? :D
 
It isn't a very sophisticated engine in these old twins.... I have had a plug rattle loose before, I can't remember which bike it was on, R100RS I think - it didn't make a huge difference, except the noise changed. I just screwed it back on and carried on - finger tight plus a little nip is plenty good enough and not stressing the threads. On racing powerboats, where everyone had the exact same, untuned, boats and engines. The most you were allowed to do was clean the hull bottom. On motors, they were all serviced by Honda themselves and propellers were allocated by lottery. So if anyone had 'tuned' a prop, someone else could likely as not end up with it. To gain an extra 1hp, possibly, we used to mark on the ceramic of the plug where the electrode gap was - and tightened down so that gap line pointed at the inlet valve. It might have given us half a boat length over 10 laps of a 3 mile course....maybe not, but the real benefit was in personal confidence. You felt like you had an edge!

On the road, does it really matter? You have 50% more power than you actually need anyway.
 
Wobbly65 said:
I see. I thought you were looking for opinions not validation. My mistake.
Click to expand...

No.. its more a BEWARE as IMO an uncrushed washer over time can only go one way.

If the plug becomes lose, it will also lose its earth to some extent... I'm not electrical so can't comment on the end result of this... overloading the system or spark eroding the thread maybe ;)

In reality, the cap / coil should keep it in place so I can't see it unscrewing... just thoughts as to a potential issue :)
 
Bottom line on this thread......
The OP, who claims to be an engineer, Is very concerned he is being ridiculed for asking about torquing a spark plug .........
Bloody idiot.
:D
 
Onahi said:
Bottom line on this thread......
The OP, who claims to be an engineer, Is very concerned he is being ridiculed for asking about torquing a spark plug .........
Bloody idiot.
:D
Click to expand...

Ay-up.. we have an 'Expert' on the job now ;)
 
Provided you don't snap them off and happy to go over the spec 12 nm all is good,
if they do work loose accompanied with power loss and a loud chuffing sound,
the coil stops it coming out and they normally screw back in, the final stage of the coil is inductive so no fear of electrical woes,
I have however had to remove many broken 10 mm spark plugs as they are fitted in cars as well, renault, ford, nissan,
the thread is not the issue , the shear point from experience is where the washer shoulder is,
sometimes doing them by feel or using a bit of experience has its benefits,
 
roamer said:
Provided you don't snap them off and happy to go over the spec 12 nm all is good,
if they do work loose accompanied with power loss and a loud chuffing sound,
the coil stops it coming out and they normally screw back in, the final stage of the coil is inductive so no fear of electrical woes,
I have however had to remove many broken 10 mm spark plugs as they are fitted in cars as well, renault, ford, nissan,
the thread is not the issue , the shear point from experience is where the washer shoulder is,
sometimes doing them by feel or using a bit of experience has its benefits,
Click to expand...

Agreed.. Ive put plugs in thing all my life.. never with a torque wrench... all I'm saying here is that by 'feel' you would do it to more than 12 Nm...

And doing them to 12 Nm does not fully crush the washer (forst time around anyway) :)
 
beaver said:
Agreed.. Ive put plugs in thing all my life.. never with a torque wrench... all I'm saying here is that by 'feel' you would do it to more than 12 Nm...

And doing them to 12 Nm does not fully crush the washer (forst time around anyway) :)
Click to expand...

If you look at the video below beaver guy put new plug in and you can see the new crush washer, he simply torqued to 12nm


 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.


Back
Top Bottom