Interesting idea from my friendly local mechanic today.
Suspected air leak on the air filter, inlet side of a car.
With the car running spray the INLET side of the engine with burst of WD40 or similar.
When the leak is sprayed the engine note changes.
NB Before anyone else says it. This is a stupid idea. Your vehicle, home, family and geraniums will perish if you try this really dangerous procedure
… and a unicorn will die …
Actually this reminds me of a technique for finding porosity in a carburettor body, as shown to me in a BMW (car) dealership’s workshop manual … 'fact I think he gave me photocopies of the pages, but which I haven’t kept …
This is a good way of finding a split inlet manifold.
I believe God, or at least his prophet Dave Richardson, mentions it in a Holy Book.
You will get an even more pronounced difference if you spray with Easy Start.
Duffo, when did any Moto Guzzi owner ever need a can of Easy Start?
Any Guzzi owner who also has a pre-war Caterpillar diesel or any WW2 American radial aircraft engine.
Now that is one smart errse answer.