Starter poblems ! hit it with hammer NO PROBLEMS plz help

[TEMPO]

OK i get all lights on when turn the key, can hear a click ( think from glovebox relay ??? ) but nothing happens.I been told by RAC that starter was knackered and to hit solenoid on starter, she fires up.
I took starter to auto electrician, overhauled, no issues for wee while 4 months. Now same scenario. Took back to auto electrician, they report starter fine. HELP
I thinkin that battery slightly losing charge and not enough initial power to kick starter ??? it is intermittent at moment, been starting ok of late, but been on few runs.
Any ideas, as mrs bit nuts on the gas when i hitting starter, and nearly took me arm off twice please help before she cashes in on my life insurance and poor old BETTY is traded in for a swish apartment in ACAPULCO
Tempo

[Oldiebut goodie]

What injun (before everyone else asks you)?

[TEMPO]

hi
air cooled 2L with twin carbs

[Oldiebut goodie]

I think all the petrol boys will guess at the starter motor bush then.

[jamesc76]

bush or earth strap, as a temp test next time just clicks put a jump lead from a good point on the engine to a good earth point on body and see if it then starts if it does its probs the earth strap!

[TEMPO]

Will try many thanks, so earthing the engine/starter to body, understand, sounds like idea