1988 k75s oil consumption, valve seals?

[xyxy]

After replacing main engine seal and rebuilding water pump my bike is now not leaking but consuming oil at the rate ~0.5qt in less than 300 miles.
I have a little blue smoke on start but not much - especially if the oil level is below the center dot.
Always park on center stand.

So this seems to be either valve seams leaking or piston rings worn right?

Related to valve seams - anyone used VITON valve seals https://www.ebay.com/itm/305574043289 ?

[Scott_]

Maybe before you go the route of stem seals and rings, I've known of a few riders that have reduced their consumption with some MMO. It took some miles and a couple of oil changes, but it did work for them on their 1100's.

[Laitch]

If that is ≈0.5qt every 300 miles, that's a lot of oil and its use at that rate should likely be accompanied by smoke or by oil infiltration in coolant, unless it is just the result a dirty oil sight glass. Consider performing a compression test and/or a leak-down test to determine and isolate compression losses.

But first, follow Scott's suggestion. 

[xyxy]

Thank you both!

I'll try MMO and I need to look into how to do the compression and leak tests as well.
I did put a seafoam a few times before into this bike.

It puzzles me that it's not smoking much too, I probably need to check if my coolant is contaminated with oil as well.