Tightening the spark plugs

[Freza]

Recently I changed the spark plugs.
Upon installation, I tightened them fairly by hand, but not too much.
After riding a bike for few days, I went to check them and found out they were loose. By loose I mean they could be unscrewed easily.
I suppose it happened because I tightened them while they were cold, then they expanded during riding, then shrunk again after cooling.


My question is, should I re-tighten them now, while they're cold? Will they cause problems once they start expanding again?

[bandit]

Tighten them when cold.

[BBROWN1664]

finger tight then 1/4 turn is the way I was always taught with spark plugs.
Should always be cold too.

[Nightfury]

finger tight then 1/4 turn

+1.
1/4 to 1/2 a turn after finger tight. And always when cold.

[Freza]

I tightened them while cold, but they got loose after the first ride. I'll re-tighten them.

[Freck]

Why not get it right, torque them up to the correct torque listed on the plug manufacturers website, or look in the Haynes manual which is in the Downloads section on here if you don't have one.
As an engineer I'm amazed at how many Heath Robinson bodges and ideas people come up with when the right information is readily available! 

[sinto]

I'm amazed at how many Heath Robinson bodges and ideas people come up with when the right information is readily available! 

I'm not an engineer though

Brilliant idea for a thread though

[Nightfury]

On the box there is normally a little diagram that shows either a 1/4 or a 1/2 turn.
I am an engineer, and I have spent years trying to find another engineer with the name Heath Robinson. All the childish comments that could be made!

[BBROWN1664]

torque them up to the correct torque listed on the plug manufacturers website

The only spark plugs I have ever used a torque wrench on were fitted to aircraft engines and were even lock wired into place after torqueing up.
On cars and bikes, especially where access is awkward, finger tight then 1/4-1/2 a turn has always worked and is what it says on most plug boxes.

[Jules-C]

The 1/4 or 1/2 turn only applies to new plugs when the crush washer has to be compressed.  It you try 1/2 turn the next time you risk stripping the thread in the cylinder head. 

Torque wrench or calibrated hands that know when to stop before something breaks are the tools to use

[Neon Knight]

Maybe the threads are already buggered and thats why they keep coming loose again ? Just a thought. 

[Freza]

Nope, they're fine

[Freck]

torque them up to the correct torque listed on the plug manufacturers website

The only spark plugs I have ever used a torque wrench on were fitted to aircraft engines

I take it you've never read your bikes owners manual then, that specifies the tightening torque for your spark plugs too......RTFM 

[BBROWN1664]

Freck, I know what the manual says but having worked on many vehicles, I have never used a torque wench on a motorbike or car as experience tells you when things are about right for spark plugs. (That and I cant get my 1/2" torque wrench in the gap under the tank on most motorbikes)