That fuse is what protects the charging system from doing damage to the MPEM,(Multi Purpose Electronic Module). I would check the charging system to see if the regulator or rectifier is not working properly. Here is some information to check out on teh charging system.
When the engine is running, set your voltmeter for 20 VDC and put the leads on the correct terminal posts. With the engine running, you should be reading anywhere from 14.5 to 14.8 VDC. (typically this test is done at 5,000 rpms) This tells you your charging circuit is good. If the voltage is higher, the regulator is bad. If you’re not showing a charge and you've replaced the rectifier, you may want to do a test on the Magneto/stator/charging coil. If you’re not a premium member and you don't have access to a manual, this test will be hard to do without it. There are 2 fuses that protect the charging system. Check the 15 amp fuse in the MPEM and the 15 amp fuse between the solenoid and the MPEM.
The magneto and stator create un-regulated AC current. The "rectifier" converts that AC to DC current and the regulator maintains the current between 14 to 14.5 volts DC for the engines operation and charging circuit.
disconnect the yellow wires from the rectifier, then plug the 5amp fuse in, tak'n that, this is the fuse that pops when power is supplied, then if it pops, disconnect the red wire from the rectifier, then install fuse again..note, don't use any thing bigger then the 5amp fuse, if fuse still pops, then yes, send the MPEM board.
It be ashame, to send out and fuse still pops. The rectifier and stator, will also cause the same fuse to pop....good luck
I hope this info helps.
Karl
