When you say master cylinder, I'm assuming you mean brakes, not clutch.
You can buy a OEM master cylinder rebuild kit for cheap. Like under $50. Check your favorite online OEM dealer. I absolutely don't trust any aftermarket rebuild kits, ONLY OEM when it comes to o rings and seals.
btw, BikeBandit is more pricey than the others, but their delivery is very quick. imo.
I use https://hollisterpowersports.com/Hom...00/fveh/124383
When putting rads, fairings, tank, etc., back in place, pay particular attention to proper wiring routes. It's so easy to get chaffed, pinched, or grounded out wires from vibration and rubbing that can cause mysterious problems later.
As stated above, the valve cover gasket is reusable. The only place that I use sealant on that gasket are the two "half-moon" sections on top of both of the cylinder heads (near the end of the camshafts). I used to wrench for Yamaha and this was recommended to prevent any leaks or seepage. I just place a very thin layer of high temp silicone (or yamabond/hondabond/etc) on the flat sections of the "half-moon". Easy peezy....no leaks.
Yes, the service manual also mentions this.
I reused my valve cover gasket too, but replaced the o-ring's mentioned. Yamabond is my choice as well, just a dab.