So the only problems with the frame were that the seat post was stuck in it and it was covered in rust.
Any seatpost with no top clamp is likely stuck in the frame. Clamps get broken off trying to use the saddle to turn the post. I tried turning it with a long rod through the hole at the top, but it didn’t give the right leverage and you don’t want to break the frame. So this is how to do cut it out:
* saw the seatpost off, leaving 1cm showing out of the frame.
* saw down inside with a metal-specific blade, starting where the slot is (the post was 10cm in).
* aluminium is soft, so it’s not difficult, but take care not to go through to the frame – saw straight, no rocking.
* when you’ve cut almost through, make another cut 5mm to the side until you have two cuts almost through.
* force a flat blade screwdriver under the 5mm slice and gradually peel it out until it breaks away.
* squeeze the protruding 1cm of post in a pipe wrench to pull the aluminium away from the steel.
It comes out as easy as you like. Sufferers imagine the parts are fused together with rust, but aluminium doesn’t rust and the seat tube wasn’t rusty inside. It’s just that a kind of galling takes place between metals that in this case produced a high friction dust that had effectively resisted all attempts to turn the post. Once free to move, they weren’t attached to each other at all, and the frame was completely undamaged.
Most people either grease the seatpost or don’t bother even to do that, so over time it gets stuck. Grease is a feeble anti-seize. You need copperslip – the copper granules prevent galling. Grease is for moving parts, use copperslip for all other parts, including bolts, bottom brackets etc.
Some would have had the frame repainted, but not me. I like original paint and original decals. I don’t like spending money. 90% of the paint was fine, so were the decals and all the rust was all on the surface, so it was a good basis for a repair. Rust coming right through means moisture inside the frame, the structure has lost its strength and you need a new tube, but surface rust doesn’t affect structural integrity.
I went around the frame with a fine craft file, filing away all brown material and bubbles with rust underneath. Then treat the bare areas with Hammerite Kurust, which converts remaining rust traces to a stable material which can be over-painted. Nothing beneath the new paint will continue to rust.
You can’t get a perfect match between metallic and flat paint (the frame is a nice metallic grey/green), but the worst areas are out of sight, e.g., under the down tube. This is a rider not a museum piece and nobody notices the repairs. Even when shown them, people say ‘where?’
I don’t think it’s necessary to get a frame like this repainted. It costs a bomb, it’s fragile and it never quite replicates the original look. If you ride it properly, you won’t be able to see the paint for mud anyway.