Wolseley wd2 metallic knocking noise on startup and off

I have a wolseley wd2 . It runs nicely...but when first cranking over there is a loud metallic knocking sound (sounds like it's coming from the governor casing). When the engine pics up...the sound goes. When turning engine off (by mag shorting button) the knocking noise comes back until revs are very slow and impulse clicks back in. I have adjusted the governor...all looks OK in the casing..and speed control by the speed knob is good. Does anyone have any idea what this noise could be please....or is it normal for a wd?
Thanks

It's the trip mechanism in the back of the magneto, as the engine slows down the centrifugal force weakens and causes the weights to fly out which are released to spin the magneto faster than the engine to create a better spark for starting

Thanks for your reply. I don't think it's that. I can hear the impulse mechanism clicking when the engine slows down.( I am familiar with impulse magnetos) It's definitely a metallic knocking as the engine first starts and builds speed. ( lasts 3 or 4seconds) . When up to speed the knocking stops. As soon as the magneto is shorted for stopping the sound comes back. If I remove the spark plug and crank over fast by hand all sounds smooth and OK.

Low oil pressure ?

Woodsman wrote:Low oil pressure ?

You don't get oil pressure issues with splash lubrication, if its lack of oil you make get constant knocking but if its like a Lister D they will still run quietly without a big end, at the GDSF one year my Lister D started shrieking so I stopped the engine and looked in the sump to see loads of white metal in the oil, I cleaned the sump out refilled with fresh oil and ran the engine for the rest of the rally with no issues and silence, when I got home I fitted a new big end.
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Maryalice

Probaably the governor weights, they do thrash around until speed picks up and it's quite normal.

Pete.

Thanks for all your replies. The governor weights "thrashing" does sound like the most likely explanation.

Ah, splash lubrication - duh. Never owned one so stabbing in the dark failed again! Cheers ma.