Help MC22 loud thunk when starting

So just in case someone finds this thread five years from now, it was the starter! Bought a second hand one and it works beautifully, better than the old one ever was.


I wasn't able to open the old one as there was one screw that was seized on and my mate's impact driver bit was too big.

In the end I wasted a bunch of money because I was impatient - I bought a new battery ($80), reg/rec ($20), and starter solenoid ($40).

Thanks to everyone for all your help!

 

At least they will be useful spares.

 

I'm sure happy to hear my theory of something inside the cases tightening up was wrong for your sake. I like happy endings...