Yeah, i know. Somebody will be doing a face palm at the thread title. Quite rightly, I'm a mechanical numpty.
Any hoo, I will lay my ignorance bare for all to see. Two things.

My Mk II powervalve is very stiff, can't move it with my fingers. When I take the header off, as per the FAQ, how do I clean it? Do I have to remove the valve and rod as per pictures and discussion in other power valve threads or can it be done in situ? Slide hammer? Eek! Not on your Nelly.

Second question.. It looks like their is oil in the PV servo motor. I noticed it dripping when I tipped the bike onto a paddock stand. Is the bubble underneath a drain cap? Where would the oil be coming from? I guess wicking through the wires or PV cables. Very mysterious. Not sure if it's gearbox or 2t at this stage, similar colour.

Will give it a good clean and see if I can find any clues, I was hoping just to put a new pilot jet and o-rings in the carb today.
Oh well.

A less complete task of cleaning the P.V. can be done with the valve in situ,but for a more comprehensive clean either remove the engine as one lump,or take the head off.Oven cleaner is good on carbon, but careful with that stuff, where you put, and where it goes.
De-gunge the exhaust as well, that's likely to be well munged up.
Check the cables are nice and smooth in operation. LABEL for correct re-assembly. Check their settings and free play.
The oil is probably from the cables, so at least someone has oiled them.
The sight bubble I believe is to inspect for water ingress, though purging water out of the cables might also be a feasible, other peoples views?
Mike

Well, a day of much faffing revealed the PV exhaust butter fly to be clean as is the pipe, no noticeable carbon build up. Cables may be a little bit sticky. Could the cable lever nut be over tightened? The lever moves ok by hand once it is off the top or bottom of the stroke, just the initial movement is stiff.
The servo did indeed contain a little oil, but not as much as the drips indicated. I learned that under no circumstances should the little bubble be removed. It immediately shrinks to half the size and needed an hours gentle persuasion with a heat gun and Anglo Saxon prompting to get back on. The exhaust flange was designed by the Devil himself, too. That needed 3 cups of tea, a bacon sandwich and half a packet of chocolate digestives to get located.
I may take the bike to my local, friendly bike shop and let them have a quick squizz at the power valve. Normally they only charge me a token few bucks for my stupidity.

Cheers for the reply.

Oh, going through the posts yesterday I noticed a comment in one about the power valve on Yamaha DT's being connected to the throttle. Back in 2012 I think. I also have a DT 230 Lanza and this is indeed the case. Just thought I would mention it in case it comes up in a pub quiz.

if its sticking at the extremes of travel it needs a clean. dont know the construction of the MKII but if it comes out then take it out to clean it properly. splooge can get behind the flap and cause it to become sticky.

Cheers for that. Will add it to the list.