An update - the engine is finally in bits. I only got so far with it, but a mechanic has continued and called me this afternoon.
Apparently the guides are worn away, the chains are stretched, and the sprockets are worn away to being discs with some pointy bits on them. The chains had started eating into the engine!
I'm going to go over and take a look in the morning.
I did some research and a set of chains, sprockets, tensioners and guides is around 400 quid. To change the upper chain and sprockets I guess the head also needs to come off? At the moment the sump is off.
Any initial thoughts on what others would do? My fear is that the engine is way past its best (it's done 343K!) and not worth investing time and money. That said, it ran beautifully before. I also don't know if there's valve/piston damage - that said it was running, just very noisy and difficult to start.
Also, any pointers where to get the parts at a better price? So far I priced up from Island4x4 who I usually use.
Any guidance welcome. I miss my Rangie!
Cheers,
Paul