C50 Rear wheel spoke issue
 

Hello everyone,
I took my 2005 C50 to a few shops to find why there's a clunking noise coming from the rear brake drum.. Nobody could figure it out, so I decided to dig into myself. I found that there were 2 loose spokes that are causing the noise. I can't find the torque specs so I can try and tighten them to see if that helps. I don't want to over tighten them and possibly puncture the tube. Does anyone know?
Thanks