Does anyone of you changed valve seals?
any tips? I do not have special tool to remove it

I heard that I should cram into the cylinder air from air compressor (8bar for example)

Do you at least have a valve spring compressor? Once the shim and bucket, spring and collets are out of the way, that would be the first requirement, then just press the valves stem down through the guide and the old, hardened valve stem seals will pop off the stem. They might require a sharp tap. A punch carefully centred would do the job.

I have changed the valve springs in a car using compressed air to keep the valves up. I made an adapter by breaking the center out of an old spark plug and welding an air line connector to it. I didn't have a suitable valve spring compressor, but did have help. One of us pushed down the valves with a ring spanner and the other one picked out the colletts. Same in reverse to replace them. Might not be so easy on a K-bike as you would be pushing sideways. You would want to have the bike well tied down to prevent it falling over.

Avenger GT wrote:You would want to have the bike well tied down to prevent it falling over.

I removed the engine outside the frame

Are you sucking a lot of oil on the overrun so that when you accelerate there is a lot of blue smoke? I ask because the valve oil seals are considered pretty reliable on these engines.
Regards,
K-BIKE

maybe you're right, maybe I gone too far with these valve oil seals.
I don't have a cloud of blue smoke behind a motorcycle during acceleration, in the morning she likes to smoke gray awhile.

Grey white usually in cool humid weather is condensed steam. Are you losing oil so you have to top up. Valve seals normally only allow lots of oil down the stem when the engine is on overrun so there is high vacuum. That sucks oil down the stem and guide gap and when you accelerate the oil burns giving the blue smoke.
Regards,
K-BIKE

Hey, I managed to purchase original valve seals dedicated to the engine in K100 RS (Goetze), but I also bought prophylactically the same ones from Victor Reinz. The only issue with the OEM ones is that they are a bit old (30 years). The Goetze ones are soft and do not have any cracks.

I think we must present you with an award for the longest gap between the original post and a reply.

If the award does not exist, then we will create it for you.

I would trust older seals if they've been well kept in their packaging. Think of how long they last in their intended environment.