Katana 750 smoking blue - rings or valves?

So my tired, abused bike that I resurrected last winter has treated me pretty good all summer.  Never left me sitting and I was able to put on some significant miles this summer.  Our riding season is drawing to a close pretty quickly I fear, so my attention has turned to perhaps resolving the only major issue I've discovered over the off season so it's ready to go next spring.

The bike starts very well, hot and cold, and really runs pretty good overall.  But it does consume some oil.  I have to add about 1/2 liter every 3000km or so.  So not ridiculous I don't think, especially given the 5L oil capacity.

The only time I see it visibly smoke (or those riding behind me see smoke) is after the engine is completely up to operating temp (which is bloody hot on these old oil cooled Zuks), and I sit at a traffic light idling.  When the light turns green and I get on the throttle, it puffs a significant blue cloud that mostly clears up by the time I'm through the intersection and grabbing 2nd gear.

My gut says valve seals/guides.  Not sure what type of seal is used on these, but it seems more likely than rings to me.  Any opinions on this?

Guides.

1/2L every 3k is nothing. I wouldn't touch it

In American, that's what, about 1/2 a quart ever 2k miles?  I wouldn't touch it either.  Every 4th time you're supposed to lube the chain, top it off.

Ok, thanks for that input.  I'm not too worried about the rate of consumption, I just don't like the smoke show.  It's better than a new bike payment I guess.

I don't really remember the details on this bike.  But a "tired, abused" motorcycle that burns oil probably needs both rings and guides done.  Maybe get a parts bike or motor/trans on a pallet from somewhere and rebuild in your spare time?  They made millions of these things and I bet parts aren't that expensive.  

If you really like the bike or see it as a good bike to build on, why not?  I'm just not that excited about Katana's although on paper they have a lot going for them.

^  yeah, I did a thread on it, but not really a "build thread" as I don't have the patience to do one properly. 

It just rolled over 70,000 km, so only 42,000 miles, but I think they've been very hard miles, and the bike showed lots of neglect, abuse, and general hackery when I got it, hence the $300 price.

It's actually surprised me.  I bought it as a project, and entirely planned on flipping it or dumping it at cost after riding it a few times but it's really grown on me and I think I'll keep it around for a while. I'm sure others would not agree, but I think it's got character.  It feels pretty good for an old budget bike.  I've done a few short road trips on it, it's very comfortable and dead stable at speed.  Excellent MPG too.

I think likely what I'll do is try to find a healthy Kat 1100 or Bandit 1200 motor and swap it.  They are more or less plug n play other than a few minor wiring details.  With better cams and a good exhaust and tune, the Bandit 1200 motors are good for about 130hp and 90-ish torques.  Not too hard to find in theory.

Here's what I turned it into:

It's 99% valve seals, but like others have said leave it be, old oil cooled bikes are hard to kill.  By the time you do the seals you end up with a large case of "youmineaswellofs"  Well I'm in this far...I'll just pull the head do guides and 5 angle valve job oh heck lets port it and do cams and... and... switch to 20w 50 like Spectro 4 or  VR1 and ride it don't hide it.  :)

Supposedly the Kat intake cam is pretty much the same as the GSXR exhaust one, and GSXR intake cams are cheap. You kno, while you are in there...