I have an 81 Yamaha XS400 and I cant figure out why it quit running. In the fall it became harder to get to started until it wouldnt start at all. It turns over and gets fuel but no ignition. I replaced spark plug/wires/battery, and rechecked all of the connections on the bike. If i take the plug out and ground it to a frame it will spark but if I just hold it without grounding it wont spark at all..Can anyone give me some suggestions on this. Ignition coils maybe, Starter Solenoid ? lemm know thanks guys!!