There could be a lot of reasons for this. Typically, if it blows instantly, for example – when you replace the fuse, this means that a device in the amplifier, typically a switcher in the power supply or an output device is bad.
If, on the other hand, it blows after playing for a while. Then it’s a whole different issue. This could mean that either the gains are set too high, or the load impedance is too low, and/or the power/ground connections need to be checked.
Another problem could be that you are using CCA power/ground wire and not oxygen-free wire (Or OFC). This makes a huge difference.
Never…. repeat. Never use CCA wire in any audio system… ever!
If you are blowing fuses, and it takes a while, meaning more than 30 seconds Then you need to start testing for voltage drops. Check at the battery, before and after the fuse, and at the amplifier power input. Two tests – Before powering up the system (at idle) and at full power (playing it LOUD) what is the voltage at these 2 points? Anything larger than a 0.7-volt drop in voltage is not good. Voltage drops can cause overheating and excessive distortion. Fuses are there to protect the BIKE…not the amplifier(s) The fuse should be ½ MAX current draw of the system. 1000 watts would be 116 amps FULL POWER Current draw,…so you should use a 60 amp fuse to protect the BIKE. NOT THE AMP!!. 500 watts would be 30 amperes and so on and so forth.
90% of the time it is a voltage drop or the charging system just can’t keep up with the audio system. Testing is the only way to know for sure. NOTE: replacing the smaller value fuse with a larger value fuse will cause all kinds of issues. If there are voltage drops because of using CCA wire, then the wire will get REALLY HOT. Possible causing a fire. Since the power wire is extremely close to the fuel tank you need to be extra careful. Voltage drops equal heat. NOT a good combination.
Test. Don’t just guess what is going on! TEST!!!!