Brake Fluid Service - 5 minutes to improved lever feel

 Typically the bubble bleed will work on the M820 Saint brakes. They do have the bleed access near the top of the lever (sounds like you've been working with that already). If you're not seeing bubbles come out with the funnel and still have an inconsistent lever feel it is likely that there is a bubble deeper in the system. On the rear brake bubbles sometimes will get stuck in lateral sections of line and have to be worked to the lever. Lever feel is very rarely, but occasionally, affected by piston motion - insure that all four pistons are working in unison. A sticky piston or pistons well out of balance (equal distance of drive) will cause problems. Is there evidence of leaking from the lever? A failed bladder can create inconsistent issues as well. Hope this provides some direction to review..

 @Nate-at-BikeCo-com: No leakages and I use the yellow block for bleeding so the pistons should be centered. I was also knockig on the line when I had the bike hanging on rope to get the line horizontally so I had both hands free to do full bleed. They are like five moths old so I hope it's not the bladder. I will try to extend the pistons, clean them and lube them a bit with the mineral oil. Do you know how far can I extend them? 5mm each or more?

 @raidenCZE: you don't need to extend them very much at all. Make sure that they are all moving at about the same rate. don't drive them all the way out or it's a ton more work. I don't have a measurement for you on that.

if you can't find the solution check into your warranty before you go too far and break something you can't fix...

 @Nate-at-BikeCo-com: Hi, so I did it as shimano dealer instruction says and I drained out all the mineral oil in adition. Then I filled the brake with fluid again and followed the instructions. I spend like one hour doing it, but the lever is pretty hard and consistent now. Thanks for your inputs mate!

 Thanks for the comment - on the rear brake (as shown) this works well. Front brake you hit the nail on the head - loosen it slightly on the bar to keep it at the highest point for sure.

 Correct, a first for me to see a right hand rear brake

 hahaha - ya you're used to what we call "moto" style in the US sounds like. I almost ALWAYS end up with a bike in my shins when I take moto style bikes off our racks pulling the wrong brake

 I cant imagine swapping over from a moto to a bike and having to change my thinking regarding front brake position, that would make my head explode haha

 Yes this more of a maintenance. There is a write up coming on Tech Spotlight this Tuesday that will touch on it more. The bottle is inserted and twisted against the threads (it isn't a threaded bottle). The write up will go through the service tip to tail. Thanks for the comment!

 Hayes kits for those exact ones. Likely craft store or good hardware store has something similar.

 These bottles come with Hayes kits. Likely something close is available from a variety of hardware or craft options.