O-rings are a better option than the seals.

Yes, if you can anchor them. They tend to move outwards

Has anyone increased size of the breather "jet", located left side power valve.
It seems pretty small hole, and of course it was clogged useless.
Old bike had bigger caliber, and I believe also bigger drain hole in cylinder wall.

Stock S3 piston ring ends are close together and travel through port, while vertex has them spaced, never leaving the wall.

That jet is just a drain, the hose is clamped off from the factory make sure it is open. Never had a need to make it bigger.
Re the rings, most manufacturers have differing thoughts on them. Some have the gaps in constant contact with the wall, which I prefer, others have them passing over the transfer/boost ports. They are small enough that it isn?t an issue.

I did increase the breather hole to 1.5mm, as it was stuck with gunk. Tube is not blocked at the bottom, but joined into "Y" with other side breather, and then out.

Just had the head cut. Old piston squish was 2mm. With new piston was 1.75mm. Cut it to 1.24mm.

Since new piston is apprx 2/10mm higher, he said to use aditional base gasket, to correct port height to piston crown, as it results in 4 degree difference, which could affect top revs.
But I think, those engines aren't so picky, to really need an exact match to previous piston, since you can get them delivered new at very different settings, 200 rpm give or take.... Also exhaust port is perfectly lined up. From factory, one 0.5mm base was used. Will see how it behaves, and adjust if needed.

Head depth was also adjusted, have to measure compression.

The small drain port in the power valve chamber will have to be drilled out too.
Just be aware that this can change the power characteristics of the engine.

Chamber hole still much larger then the increase I made, so will keep it stock for now. Cant see the drain affect engine. I see the small hole as an eco drippage preventer and floor stain after use minimizer. Bandage for overly rich bike when stock.

Breather bolt, LHS

Two options available -
- 0.5mm, called a devap., whatever that means, deeaporate??
- 3.0mm, probably stock non eco friendy, ment for direct-out hose routing, for free spill

So it is a tunable part, and both are speced for 2018 model, didnt check other years.

The 3mm fitting is for the transmission vent- top right of the engine.
The .5mm one is for the power valve drain.