"motion sensors are pretty rel
"motion sensors are pretty reliable. I would suggest checking the cap and low oil sensor in the upper oil reservior. you can check with a simple ohm meter to see if a signal is being sent. The most frequent culprit seems to be the alarm sensor module (black box mounted on port side of motor). These are pretty bad about going out and sometimes they do it gradually, producing an alarm at times and none at other times. I just replaced one on my 90 XR4 for about 180 $ and solved my problems. There is a fairly complicated diagnostic test you can do with a simple volt/ohm meter to determine if this is the culprit. Part of this diagnostic will also help you rule out the motion sensor. You basically test the lead out of the motion sensor with a voltmeter. Keep the engine from starting with your kill switch and turn the engine over with the starter (protect your impeller with a drum of water, garden hose suction cups, or boat on trailer in water). For each revolution of the crankshaft you should notice a voltage pulse (easy to see on a digital voltmeter). If you see the pulse, most likely the motion sensor is working. There are several posts about these situations on the net. I can get more specific about my procedures if necessary. Good luck."
