When it comes to adjusting the chain tension and the rear wheel, I get nervous!! So, I just put the rear wheel back on after getting the bearings pressed in. I don't go by the markings on the swingarm, instead I use a ruler and measure off of the adjustment blocks. I have a question about how close the measurement can be that's considered "good enough". In the pics below, on one side I measure around 25-3/4mm. On the axle nut side I measure right at 25mm. Is that close enough to be okay? Or should I re-adjust and get it closer? Thanks for that help!
I'm kinda fanatical about that too, particularly on my road/track bikes that are going to be going over 100mph for extended periods! I started using a little Motion Pro alignment tool https://www.motionpro.com/product/08-0048 to make sure the chain is *absolutely* straight! That's the key, not where the blocks line up. If the chain runs truly straight between the two sprockets, no power is lost, and wear will be as minimal as possible.
Read the owner's manual for the correct amount of drive-chain slack. Most street bikes also have a sticker on the swingarm. With the engine off, put the bike on its side stand or center stand, and shift the transmission into neutral. Find the midway point of the chain between the front and rear sprockets. Push up on the bottom of the chain and note the distance between the full-slack (lower) position and the no-slack (upper) position on the bottom. 1.2–1.6 inches (30–40 mm) is typical for street bikes, while dirt bikes may need 1.4–2.0 inches (35–50 mm) of slack. To adjust the drive chain, loosen the axle nut a couple of turns. If all you have is a short wrench, you can stand on it to get the nut loose. Most street bikes and some dirt bikes feature bolts that you turn to increase or decrease the chain slack. Adjust them a quarter turn at a time; be sure you make the same adjustment on each side of the swingarm, so the rear wheel stays aligned. Measure and adjust until your chain is within spec. Whatever system you have, when you have the correct chain tension, remember to tighten the axle nut back to the correct torque (check your manual, but usually to 65 foot-pounds or 88 newton-meters).