Cylinder Head Out

Hi
My 650 Terra from 2013 have started to burn oil heavyly.
Could be the valve gaskets?
The cylinder head gasket?
Or the cylinder itself?
Anyway, anybody have this problem?
What compression preassure could one expect?
Is it possible to get the cylinder head out without taking the motor out?

How dirty was the air box and throttle body?

if you're still using the stock airbox and did a lot of dirt riding the engine may have sucked in dirt. In that case i'd suspect worn piston/rings/cylinder. But first check if it's burning oil that's been pumped into the air box and then got sucked into the engine. This is quite common when the engine got overfilled with oil.

You mean if the oil comes through the crankcase ventilation. No, the airbox is clean.

The problem is the opposite. The oil level goes low with about one litre/ 750km. And it comes out through the exhaust pipes.
if I start it after a couple of days a black cloud comes indicating that the valve stem seals are to blame. Oil got time to zip down to the cylinder.
On the other hand the compression pressure is only about 90 psi (if I measure correctly) indicating the piston rings are worn.
What compression pressure could be expected?

But everything is strange, it has only run 15000km (330 motor hour). There should be non of those problems.
I am preparing my self for removing the cylinder head or maybe the hole cylinder.

I'm curious how you measured the compression. There is a decompression lever on the inlet cam that only disengages when the engine starts. Surely this would prevent accurate compression testing using the traditional compression tester?

Aha, thats news to me.
You mean it sort of let out compression to make the start easier?
So how can the compression be measured?

https://faq.f650.com/FAQs/CompressionTestingFAQ.htm

almost the same engine and procedure.

I'm not sure how to do it hence why I'm asking. An alternative would be a leak down test.

Sussurf is right for the leak down check. WARM ENGINE CHECK...(everything is warmed up and in place/expanded) Get it on top dead center on the compression stroke(make sure your not opening the exhaust valve) then hook up the air(you don't have to have a leak down gauge you can give it regular shop air). You will hear hissing air leaking by the crank case vent(piston ring failure), coming thru the throttle body is intake valves and hearing hissing air thru the exhaust pipe is exhaust valves. Make sure you are feeding it at least 100-120 psi(good compression values). COLD engine will be lesser psi values.. Warmer the better..