Torque Table

I think the spark plug torque has gone down from 20 to 16NM?

Sean this information is very old, the thread is from 6 years ago.  Since that time the spark plug supplier is no longer NGK, it is now the branded Rotax plug.  it indeed has a lower torque setting. 

The only reliable way is to follow the latest heavy (HMM) manual for the engine type you are working with.  At the first pages of each section there will be an illustration that shows the values and any liquids, like Loctite, that may be needed.  

Attached is the example from the latest HMM for the spark plugs (Rotax) 

Cheers