Thanks Freebird for your help. When I next started the mower it worked fine so no further changes were required.

For the last few weeks I have been researching rust. So many methods available on the internet but most worked well on unpainted parts. What I wanted was to remove the rust with out damaging the paint and original stickers.

I ended up purchasing a product called Evapo Rust. It's a non acid based product. I tested first on the air filter lid. Here is how it turned out.
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Next I removed the cowl and submerged it in the solution. Here are the results.

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It's not perfect but it has cleaned up well considered the age.

Please let me know if you notice anything else in the photos.

What should I now do to these surfaces to prevent rusting again.

Also the starter cable is now grabbing a lot and not retracting very well. Is there any good threads on here describing how to diagnose this and get it back to normal.

Appreciate your advice

DonnyW