Cylinder repair/replacement

I have been resisting the urge to open my engine to fix an oil consumption issue. Not 100% sure what the issue is but I can assume it's piston/ cylinder/ ring wear. If during a tank of fuel (26ltr Safari) I cruise at 120kph I find I'm burning about 200ml of oil. However when riding under 100kph I don't use any. Gear ratio is 15/44 so its not revving its face off. Don't notice any blue smoke when revved stationary, power is still there too.

Before I get stuck into it I need some info on whether it would be cheaper buy a new cylinder as opposed getting it replated/ Nikasil. What have others done in the past? I would prefer to keep OEM piston for longevity as its long distance stuff I do more than racing around on the streets/tracks etc.
I should just keep throwing oil in it until the power starts to drop off..

Ambient temps can get quite warm here so usually run a 15W-50 however since the oil issue was discovered I have tried 20W-60 to see if that would change rate of consumption, which it didn't.
The bike has about 25k on it, I'm hoping if/when I open it up the bore will be in good shape and I can get away with rings and gaskets only.
Still a bit confused with the oil consumption I'm getting although I have read of others experiencing the same/similar symptoms.

How many km you do between oil changes ??? mine is 2000 km service interval, does not use a drop , i don't cane it to death but also don't baby it, i use 15W-40 Gulf Western, temps here usually about 20-30 celsius .Sort of expecting the cam chain will die before the piston and rings, and yeah i prefer to stay with stock parts and specs. too,seems to give the best longevity.   

Do a leak down test, it could be the valves causing the problems....

I have noticed one thing about the xr engine , the cylinder its very wear resistant ,  and this is just my opinion but many owners have wasted money on a new one or replating  on a perfectly good cylinder  , all you need is a new piston and rings  , i would change the timing chain for piece of mind and inspect the conrod  as they are notorious for failing especialy if you had ran the bike low on oil . As for the oil usage , its normal and most xr's do use small amount of oil , especialy when ridden hard , i ride mine like a sissy so it is not using oil .
Remember watching some videos on utube  about the baja 1000 race and when the bikes have stopped for fuell and new tyres they have topped the oil , so on a tiptop condition race bike  ( they know the beast and know how to service it , the engines are stripped and checked  before every race and parts are replaced when needed )  there was some oil usage . Just keep it topped up and ride it .

I have been changing oil every 1000klms, sometimes twice in that period due to the oil not being left on the stick and not knowing how much is in there.

Mauser, could you explain your valve out of spec theory please? Do you think the the oil usage is via the stem seals?

Mad Frosty, my first reaction was to sell it when I found it using oil. I've not owned anything that has used oil before. However I can't sell it knowing its got issues, karma will bite me back later in life. If I'm going to pull it down and the cylinder looks fine and in spec then I'll throw a piston and rings at it. Cam chain, check cam and guides. Send cyl head off for valves, stem seals and guides.

That should cover all my bases if I do decide to pull it apart.

Not out of spec...worn valve seals...causing oil to get past them ?

Most certainly is something that needs inspection for sure, might see if I can locate a leak down tester just to identify where the possible issue is going to be prior to anything being removed/ replaced.

Rings/ cylinder might be fine.
Starts fine, idles fine and as mentioned power is all still there just consuming oil like nothing else I've owned before.

Just don't know why I cant see any oil burning when revved from a stationary position, would think if it were stem seals I would get the blue puff once revved up.

Valve stem seals most likely, maybe some pitting of the seats as well...... I'd take the top off and check it.
If I'd find both then I'd not put new rings in, and you probably will find the bore's fine.
If you find worn/pitted seats better pay attention to your airfilter - not a cotton gauze one but foam only, not over-oiled, properly sealing and cleaned regularly.

I'm not saying that there isn't anything wrong with the bike, but like Frosty says, I don't think it's unusual for an XRR to use a little oil when ridden for sustained periods at 65+mph speeds on the road. There's plenty on the www about this. Just google "xr650r using oil".
Mine used about 500ml during a one week, 2000mile road trip recently. I had to top it up at the end of every day. But it never uses any oil when I'm green laning or pottering around the local roads.   

Zoro, my bike uses the same amount of oil as you described, I just performed a pressure test and everything was spot on then I pulled the head and jug for inspection.  Rings and cylinder look almost new but it still consumes oil and its consumption has a direct correlation to how its ridden.  If im just putting around all day low and slow oil consumption is very minimal but on days when im flogging it I see the same oil use as you, I have to add oil pretty much every ride to keep it topped off.  If its running good I wouldn't tear it down and throw a bunch of money at it just to find out it still uses oil when its all rebuilt.

Have also seen the many posts regarding the oil usage in these things but one thing the testing cannot account for is the stem seals as a couple of guys have pointed out already.
I would keep it the way it is if I knew exactly where the problem was, I just don't like having to worry about the oil and how much is/ is not left in there when riding.
Most of my riding is a long way from help and on my own.
Would be nice to be able to fill with oil and know for certain that's how much is going to come out when I drop it in 1000klms.
Plus, with my Wolfman Panniers 1ltr of oil takes up a fair amount of real estate, not to mention the constant worry about the oil level whilst riding.
It does take some of the enjoyment away from the whole experience...

The stem seals are cheap and easy to change so if you think they might be leaking just change them , for the piece of mind . It would only make the bike better   

I agree it probably is valve seals and a compression test wouldn't show that.  If you get to the root of the problem please post up your results for the rest of us.  I will continue to support the petroleum industry for the time being.  I thought I sold all my two strokes.

Think I will replace the stem seals, biggest cost will be the head gasket most likely.
Luckily I have access to a glass bead blasting unit so I will give it a good clean up with that too.
Provided the valve seats are in decent condition I'll run some lapping paste over them prior to re-assembly.

I'll go and order the parts today, they should be here in a week or two.

+1 on the seals mate , mine has never used that much oil hard or slow riding .Oil sight tube if you dont have 1 install 1 ,its the best mod on this bike and a must have , i can check oil level on the fly , when its running hard the oil is down the bottom of the tube when cruising its a few cm from the top at correct oil level , its a must have and if ya handy with tools its an easy job
sending my motor down to teknik and getting nick dole to rebuild her there and back should be 3k top and bottom end , he told me to then expect another 90,000+ from it , he also told me i had looked after my bike if it had 90+ and thats what these motors should get if left stock and looked after ,i only use mineral oil , 3 k changes   

Nick was the one that told me to use only OEM pistons for their longevity.
He also gets the cams ground similar to the HRC cam

Sean-0  what conrod have you ran in the bike , was it the stock one ? All the SuMo people claim that they are no good especialy if you rise the compression ratio litttle bit , so i would be impressed if your engine managed those miles/km's  on the original conrod  

not to go to off topic from zoro's post but mine is stock rod stock clutch ,mods are stage 2 cam fitted around 50,000 kms tm 40 pumper at i think 85,000 , these bikes will do 100,000 kms if looked after , i commute it ,i desert ride it , i single trail it , it does it all