The RC51 is one of the most reliable engines Honda made (per UK bike magazine).
I've got over 40K miles on mine and I've heard of others that have 60K+ and even 100K miles.
The valve check internal is every 16K miles, and from 24K to 40K miles I only had one exhaust valve barely out of spec.
As with any engine, routine maintenance is the key.
Treat her lovingly and she will reward you.
And since Guam has a lot of salt air, buy a tube of dielectric grease and apply to every electrical connector you can, including the battery posts.
It waterproofs, prevents corrosion, and lubes the connectors.
Also put a dab on the spark plug boots and caps, it will prevent the rubber from bonding to the plug porcelain.
Do they still use shells mixed with asphalt to pave the roads?
It's been ages since I was on Guam. Where do you find the roads to open her up?
It's not a huge island.
There used to be a long stretch from Agana down to the tip where the Navy base was.
Of course you had to watch for the crabs on the roads at night.
You can choose from many different brands of sprockets.
For the rear you can use steel, aluminum, or a hybrid of both (Stealth sprocket).
A set of sprockets might run around $100 more or less (no chain).