If you don’t have a grinder but you do have a cordless drill you could get an Arbor adapter to take a grinding disc- it’s a little slow going but will grind the pins enough for a breaker tool to push them through. Needless to say, wear goggles/safety glasses!
https://rover.ebay.com/rover/0/0/0?m...2F273520091558
Alternatively if you really don’t want to grind the pins down and you have a rear paddock stand and a means of unloading the rear suspension (I use a ladder and tie down straps for this) you can detach the suspension hoop and with the rear wheel pushed all the way forward, just take the chain out sideways- the beauty of the trellis frame coupled with the swing arm attached to the engine case.
Then while you’re there you can also clean and re-grease the linkages and/or replace the rod end bearings in the hoop.
Just had a thought- if you have standard footrests you’ll also have to remove the near-side one in order to get the chain off without splitting it.