Main Motorcycle: '08 Speed3
Join Date: Jan 2008
Location: Clearwater, FL
Other Motorcycle: '99 TBird (sold)
Ok, this is simple. If your bike is cranking for a short time and cutting out, it's just not getting enough juice. If it cranks forever and won't start, that's a whole different set of possibilities.
So... start here: is the car running? I'm going to guess "no". If it is, it will have more than enough (too much, really) juice to fire your trumpet. It is not a good idea to jump a bike or similar smaller electrical system with a cage... but it can be done.
If the car is running, give it a bit before you hit the starter. Once it fires up, of course you want to take it for a nice long run before shutting her down. Then, the next day, you'll see if your old battery is holding the charge.
This will at least let you know if the problem is with the battery. If it fires up and runs, but won't run tomorrow, you clearly need a new battery. Pony up, get one and put a nice slow charge on it. If it wont start even with the overabundance of power, start over.
Let us know... it really sounds like you just need a new battery