I'm about to give financial advice based on incomplete information, so keep that in mind. Also, I'm not licensed to give financial information to people, so keep that in mind too.
How much are you saving per month to buy the bike? Is that comfortable, or do you want to drop it down a bit? I'll assume you are saving $100 a month, and can continue to do so comfortably after the purchase. After you subtract for the insurance, you have $70 a month left. What will $70 a month get you? Assuming an APR of 7% and a 36 month loan, you can only borrow ~$2,300. That means you should wait until you have $4000-$5000 to put down. By contrast, if the bike is $6500 and you put down $1,000, you will have to pay $170 ($200 with insurance) a month for the 36 month term.
Experiment with these numbers on a website with a
loan caluclator and find something that fits your budget. Remember that if you think its going to be a bit tight, it will be very tight. My strongest recommendation is to pick a payment plan that you think will be easy to maintain, because anything other than easy is hard.
As to were to go for financing? Credit Unions, Banks, Dealer/Mfg financing, Insurance agents...lots of places will lend you money. Shop around. You need to know the APR, the term and the amount borrowed. From that, you should be able to get to the payment. DONT talk about payment with the Dealer, talk amount financed.
As to Insurance...lots of options there too. Progressive, Geigo, Foremost will all insure a stand-alone motorcycle, but if you also have an auto, check with Allstate, State Farm, American Family etc. (whoever you have the car with) as they are likely to write motorcycles also.
Remember to keep your emotions in check, and if you can't afford it yet, wait. You already have a bike that works.