4T clutch strip

Spent a cracking day off work stripping my 4T engine. Got the magneto side stripped without a problem but have hit a snag right at the end of the clutch strip. Ignoring the fact that the copper shim has been destroyed and there are particles of copper everywhere (pic 2), the main problem is that I can’t remove the clutch chain wheel centre off the gearbox main shaft (pic 1). It rotates happily around the shaft in its assembly position but within a millimetre of trying to withdraw it it starts to bind and I have failed to persuade it to move any further after an hour of trying. I can press it back down and have tried twisting it off with the box in first, levering it Etc but it’s too tight on the shaft. Any tips?

Thanks JH. I'll have to see what pullers are available as the one I have has fingers too thick to get under the clutch centre as the gap is only about 3mm. There doesn't seem to be any burrs or any visible damage. It's almost like it was undersize but was tapped on anyway and has worn a tiny clearance in its installed position on the shaft so it now won't come off. You'd have thought the clutch centre would have worn though rather than the mainshaft. I did try tapping the inner chaincase off the shaft (after removing the nuts/screws) to take the clutch centre with it but access is awkward and it is difficult to keep it square.

New day, new approach. 10 minutes with a makeshift puller and significant force moving it a fraction at a time and the clutch centre is off. Max hole diameter of 14.05mm. Splines measured a minimum of 14.2mm. No wonder it was tight.
Difficult to take a picture whilst holding two spanner’s but you get the gist. I’m assuming that the hole is under size as everything else fits fine on the splines.