A few months ago, i bought a used and incomplete K100RS.
I was only interested in the papers and frame, to use it on my sidecar, which had no homologation.
So I wasn't in a hurry to collect this bike, pretty far from home, so a friend had stocked it in its barn.
It eventually was delivered yesterday by a buyer who came to buy my Royal Enfield and picked it up at my friend's.
The bike was abandoned for 10 or 20 years.

The first thing I noticed was the blurp from the Jetronic controller:



It was almost full of water indeed:





But who cares? It was a K75 controller.

So I noticed that the injectors were missing and that only the 4th cylinder had a cloth plugged in the injector hole. The others were open to the sky...




And the rusty juice sipping from a sparkling plug was not a very good presage.

So, time to use the endoscopic cam my brother offered my as present for my 50th birthday with this comment "At your age now, it may be used not only in your garage".

First the valves:







Then the combustion chambers:

A River Runs Through It. Probably an ex-Robert Redford's bike.







Should I go ahead?
No.
I won't even flush the engine. Just a new battery, il will probably start.

Definitely give it a good drain and maybe blow it out with some compressed air before you fire it up jbt.  Just to play it safe of course.

jbt wrote:Should I go ahead?
No.
I won't even flush the engine. Just a new battery, il will probably start.

It probably will. The FICU should be okay after a careful clean.

Those reddish brown stains are probably corrosion and quite possibly conductive enough to mess up the operation of the unit.

I would give that part of the board a bit of a clean with lemon juice and a toothbrush(I always use the wife's toothbrush).  Follow it with a good clean water rinse, blow or shake off the excess and then immediately do a rinse in 90% Isopropyl rubbing alcohol to remove any remaining water.  Let it air dry for an hour or so and give it a try. 

If it worked before the water got to it and the water didn't freeze, there's a good chance it will work again.

I think I won't even try to start it, as I wrote, I bought this bike only for its frame and registration documents. 
As water stayed in the barrels for years, there's probably corrosion into the barrels. So I'll salvage the engine, but will save some elements before, in particular the head to be ported and machined to receive the Luftmeister cams & valves.