Motorcycle Repair: 1982 magna v45 honda, honda magna v45, regulator rectifier

Question
i have an 82 honda magna v45 750cc. we purchased used from a person. it started fine. then a couple days later we can't get it to start but when we jump it it starts right up. it runs fine. only problem is when u stop and cut bike off it won't start without being jump. when i push the start button it tries to start but then it seems to go dead. can't figure what is draining battery. lights and horn works but not starting without jumping from car. thought it maybe starter but it starts with the jump. any ideas would be helpful. also i checked the sparkplugs and made sure they were on there tight and still had the same problem. thx for any help. rod

Answer
Rod, Check the battery first. It must be a fresh fully charged unit. Batteries don't last more than 2 years in most bikes, so if in doubt, change it.
You could have some issues with the regulator rectifier, perhaps. If the rectifier shorts out internally, the the battery can drain down through the shorted diodes.
Sometimes, the starter clutch will start slipping on a low battery condition and it can't spin the motor over enough to light off quickly.

http://www.electrosport.com/electrosport_fault_finding.html

Check the alternator wiring connector for any corrosion or heat damage. Check also the ignition switch base, to see if it is tight. Other areas to check are the connections at the starter solenoid and starter button switch/KILL SWITCH assy.

Check the battery, get it running, check the charging system for output over 13 volts. Depending on the miles and condition, the starter motor may have shortened brushes and need an overhaul.

Bill Silver