Forget the registration fees, you've got bigger problems on your hands. Lemmy break it down for you.
Your insurance costs a lot because you're young and newly licensed, because kids with brand new licenses crash more often than anyone. Your insurance suddenly costs more than the estimate you received because you didn't give the insurance company all the information they asked for. When they found out the real information, they re-issued your policy at the higher price.
If you stop paying the insurance company, not much will happen. They'll send you a letter telling you that the policy will be cancelled for non-payment, and then they'll cancel the contract. Your lender will also get a copy of the cancellation letter, and they'll come after you with everything they've got.
When you signed the finance agreement, you agreed (it's in the contract) to carry valid insurance until the loan was paid off. As soon as your insurance coverage expires, their lender's contingency coverage will kick in. The lender will add the cost of that insurance to your loan payments, and it will cost a lot more than your motorbike policy did. And if you refuse to pay them, they'll come and repo your bike.
All that will happen before the DMV even knows what's going on.