Replacing Mainspring

[nad]

Hello again , I've not been too active on this forum over the last few months but hopefully the extended festive break will give me a little time to pick up on my learning experience.

I've bought a few more 40/50's Roamers over the year that I'm planning to try and improve in the next few weeks. One in particular, a  40/50's Shock Resist with an MST 372, stops from full wind after 20 or so hours. It's keeping time to a couple of minutes over that period while  being worn so I'm guessing that  in addition to a strip & clean,  I'm going to need to replace the Main Spring. (One sourced already from Cousins.)

I've not replace a main spring  before now, and while I've read as much as I can find I thought I'd asked a few questions  on the forum.

I'm guessing that :-

New main springs come lubricated?

After removing the old one, pressing the new one into place with thumbs is not going to damage the new one?

Thanks.

NAD

[Geo]

The new spring should be good to go, and pressing it in with your thumb is how you do it. You should have finger cots on to prevent contamination. Just make sure the direction is correct before inserting!

[nad]

Thanks for the input GEO.

Pictures will be taken while disabling to try and ensure it gets inserted the right way round and finger's covered with cots.

Is there normally a hook on the barrel as well as the arbour? If so how do you get the spring "hooked" to the barrel when pressing in the new spring?

[rogart63]

It not so important to line up the arbor or hook on the spring in the barrel . That will set when you pull the crown and wind up the mainspring later. What ever you do don't try to pull the spring backwards in the barrel as that could brake it.

[nad]

Thank you, appreciate the help.

NAD