Hi again, second post here!

So the bike is a 1985 K100RS that I've had for a few months now. This ticking sound from the left side of ye engine has been happening since I first bought the bike. I changed the oil about 1000mi ago and put 20w-50 regular motor oil in it. I realize that's on the thicker side for this bike, but it didn't make any difference in the noise.

Now, I believe this noise is a lifter. And since I -think- it's only one of them, based on the speed of the tick, I dont believe it's an oiling problem, because if that were the case, I would assume all of them would be ticking.

I suppose my questions are: is my assumption correct that it is a lifter?
Are these things adjustable on the 1985 k100?
And if it needs a replacement, an approximation of price of parts (and labor if I decide to take it in)
And would an oil additive and a couple oil changes even be worth trying?

Thanks all!

The K bikes don't have "lifters" in the general term of Hydraulic lifters like auto engines.
They have the cam working almost directly on the top of the valve stem with a follower and a shim for adjustment.
If you remove the cam cover on the left side you can then very easily measure the valve clearance using a set of feeler gauges.
I would suggest downloading the clymer or haynes or OEM manual from the downloads section (you need a password from Crazy Frog to do this) and those manuals will give you a good run through on how to do the job including changing the shims if needed.

The ticking could also be an injector clicking.

So essentially, it could be a valve adjustment (the shim) that could just be a little high on clearance that could be ticking and I would just have to check that out? Is it possible that it's worn and is ticking due to that?

I've heard that about injectors as well, that they will sometimes tick. The ticking increases speed in conjunction with RPMs, if that tells you anything helpful. If it was an injector, I would have no idea where to begin as I've only worked with my 1968 BSA before. Is an injector ticking a detrimental thing?

You can use a screwdriver as a stethoscope to check where the noise is coming from. Work along the cam covers over the valves, and if one of them is noisy you will be able to pinpoint it.

Put the pointy end on the engine

Some would say that it's "better to hear the valves ticking that to not". But these valves don't do a lot of ticking. If it's loose it's a too-wide clearance issue and can be shimmed to the proper clearance as per Rick's suggestion, with the proper tools and a reasonable understanding of the correct procedure, as well as the useful info available from the downloadable manuals here.

The shims don't wear much, per se, it's the valve seat or valve face itself that wears, usually leading to an excessive tightness of clearance. If the tickover (idle) is steady and smooth and the revs increase without obvious strain then that's an indicator that the valves are likely within or close to spec.

A ticking injector is of no particularly big drama unless she runs like sh*te.

20W50 oil is a good viscosity for the mighty K in a Summer climate.

So I finally got around to stethoscoping the engine, and I actually couldn't hear any ticking noise when through the screw driver when placing it on the valve cover over each piston. I DID hear a ticking when I placed the screw driver on each injector. So I'm assuming it's just one or more injectors ticking, which is no biggie as far as i know.

Thanks everyone!

The injectors are always ticking it's when they stop you got problems.