Some things to try that might help you pinpoint the problem:
BTW, do you have the owner's manual for the BC2. You should grab that as well if you don't to make sure you have set everything on the unit correctly.
Get two ICOM units and push the bike ICOM PTT button - can anyone else hear you? Note the color change on the ICOM when you use the PTT button. If noone can hear you, then something is wrong with either the transmit on your ICOM or the recieve on the other ICOM. Try switching ICOM units to confirm.
Assuming both ICOM units check out, then plug one into the bike and hookup your headset. Hit the PTT button - does the light on the ICOM change color? If no, then it is not receiving a close signal on the PTT switch. So either the wiring/switch for the PTT is bad, the wiring to the ICOM is bad, your microphone/headset wires are bad or the intercom has an issue. Try the simple things first. If pressing the PTT lights the ICOM, then you know the wiring is okay and you have an issue with either your microphone/headset wires or the intercom itself.
Remove the rubber boot from the back of the PTT switch and physically touch the 2 bare wires together. Can you talk now? If you can, then the PTT was defective and can be replaced with any normally open switch that fits in the hole and is waterproof. You could also place an OHM meter across the switch, push the PTT button and verify that the circuit closes.
If your switch checks out, the next thing to look at is the wiring cable you made. Using an OHM meter, carefully check each pin on the intercom side against each pin on the ICOM side to make sure no wires were crossed. Then check each pin against every other pin to make sure there isn't a short somewhere in the cable. Assuming no shorts or breaks exist in the cable the next step would be to check the headset.
Is there anyone in your area with a known working headset? If so, try to borrow it for a quick test. If their headset works, then it is either your headset microphone or cables. Try swapping cables to see if your headset will now work. If it does, then you have a defective headset cable which needs to be replaced. If your friend's headset works and swapping cables doesn't make yours work and you have verified that the cables in the headset are plugged in and haven't worked themselves loose, then you likely have a defective microphone. J&M sells replacements at www.jmcorp.com
If all of the above check out, then it is likely the BC2 unit that has the issue. You could try some contact cleaner or WD-40 on the place where you plug in the ICOM cable to make sure you have a good contact point. If that doesn't address it, then the next step would be to disassemble the bike, remove all cables going to the BC2, clean them, reassemble enough to test and try again. If you still have problems, then it is likely the unit itself that will require service.