don't use WD40
I'm a clock and watch repairer and the moment I smell wd40 I curse the owner no matter how good there intentions are.
i like most reputable repirers have a big waiting list and the smell of wd40 keeps your clock at the bottom of the waiting list.
if it uses a battery and won't go check the hands aren't catching on any thing. change the battery if it's still not going fit a new movement, there only designed to work for 10 years then replace.
chat to some one who repairs them as a job (not uncle bob who tinkers on Sunday with a old mg miget )
talk is cheap get advise from local expert
for example today I was asked to fix a 15 year old 31 day Korean strike its a waste of time and money if it's sentimental I'll retrofit a quarts pendulum movement
any good clock reparer will be honest.
it's a dieing trade (in the England any way) we don't need the hassle of a badly made clocks wasting our time.
if you can't find a clock repairer search for British horological institute they may be able to help Find some one in your country
like I said it's a dieing trade do you think you could do it. the BHI are the only institute that I know of that offer distant learing courses think about it.
is it wound check the key dose it fit, can you wind it.
identify the clock type is it a wall. mantle . strike . chime .400 day. westmister. longcase.
if it has a pendulum can you get it to tick, forget if it level in the wall, listen to it. is the tick tock even. adjust the clock to allow a even beat.
when was the last service if known.
if you can get it going how long until it stops.
forgive me for not writing more. it's a massive subject subject and I'm always learning
this is a super quick guide if a old mechanical clock is broken
basicly find a expert get advice and the questions you may be asked.
just because you can fix most things, dosent mean fixing a clock is easy.
its my fulltime job and I have a 200 year old French mantle clock on my bench that won't strike at 2 o'clock it's driving me potty it's been there three months every day I try something new to no avail.
but I'm always learning I love it.
quick warning most books avalable are so overly complicated you need to be a expert to understand them.
I'll try to write more asap. but thank you for reading hope this helps if you think my English is bad whoop dee doo go fly a kite I don't care.