Loose spokes

The last time I lubed my chain I noticed some of my spokes had a dull thud instead of a ping. I got the correct size spoke wrench and proceeded to tighten them using the every 3rd spoke 1/4 turn method until all 36 were done. I then tapped them again, every 3rd method, and gave only those spokes that were not "ping tight" another 1/4 turn. After this, I still had quite a few which did not sound tight and upon closer inspection, found 3 spoke nipples were cracked. Anyone have any insight to this spoke issue? Is it common for them to be so loose? My 2008 SM510R has 2300 miles and this is the first time I have tightened the spokes. I ordered new nipples to replace the cracked ones and only used very gently one finger pressure while tightening them. This is the rear wheel, the front spokes all ping as they should. Thanks.

could the nipples of cracked due to the other ones loosening up thus creating more tension on the others? or perhaps from the others being loose it caused the others to get a shock loading effect due to hub oscillation? just a thought, idk.

Spokes stretch from new. Your methodolgy was correct but frequency was too little. I think that after the bike has done its first 100 miles is a good time to check than every 500 miles. Also every second wash put a little WD 40 on the spokes where they join the nipple. It stops corrosion.

I agree, the spokes need to be checked fairly frequently for the first 1000 miles or so, then about every 500-1000 miles or so after that depending on how rough the terrain is and how fast you ride it.
However, I'd use 'Spoke Set' instead of WD40, as it wicks into the nipple, then turns into a rubbery putty like substance - keeping water and corrosion from seizing the nipple to the spoke. A drop in each nipple lasts 2-3 years or more.

Thanks for the advice/information. I just didn't give it any thought after riding sportbikes for so many years. Once the new nipples come in I'll change them out and keep a closer eye on them. I rode today after I adjusted the valves and the cracked nipples and corresponding spokes(3) held fine. Not sure if they have been cracked for some time or if it happened when I was tightening them. I used very gentle pressure, so I think they may have been cracked for some time do to looseness. I would like too say that I love my SM510R and that I almost passed on buying it due to negative forums/internet info about maintenance, durability, parts being scarce and so on. This bike has been nothing but fun. Oil changes and valve checks are more frequent, but the bike is designed well and all that can be done in a couple of hours.

I now only do valve checks once a year or if I find it getting hard to start (hard starting has not happened as yet). I have not come across "Spoke Set" before sounds interesting though.

I had an issue when I was out riding in West Texas. I noticed my front wheel was not totally straight and sure enough when I stopped to check I had 2 spokes come loose. Good thing I didn't get a flat. The nipples were stripped so I am waiting on a whole new spoke set to go with my "ahem" new front excel rim. If I would have checked them like I normally do then I wouldn't be waiting around for new "custom spokes" I had a brain fart that day and didn't check them.

I have been told by a wheel builder that you tighten each spoke the same amount the wheel will stay true. It has worked for me. Also if the nipple gives way the spoke base is worn and they both need to be replaced.