Hi, My Stihl ts400 saw has no spark ? Can you help... Regards Griff

First try a new sparkplug. If no spark disconnect the single wire off the stop switch and trace it back thru the saw and make sure its not chafed anywhere. Do the same with the high tension lead off the sparkplug. If both these are ok the saw has a one piece cdi unit which unfortunately will have to be replaced. Hope this helps, Phil.