I have just been given a 1980 Sachs Sundancer. The engine runs really well but I noticed that after about 20 minutes If I applied the rear brake the engine would die. The engine would also would try to die if you tried to use the horn. A couple of times after it died it would not crank at all ... then if you let it sit for 10 minutes or so it would start right back up. Does anyone know what could be causing this problem. Thanks in advance.