Buying a new Bike without a cosigner

Hi i was wondering if anyone knew my chacnes of getting approved without a cosigner.

my credit score is 743 i can put a 2000$ downpayment on a 5500$ bike. I work under the table so i can't really get a proof of income and i am 20 years old. Will i need a cosigner or should i bring someone just in case?

My gf is willing to cosign for me (her credit score is ~650) and i will be able to pay it off within a month (its on sale for 2000$ off brand new so i want to get the deal while it lasts instead of waiting 1 or 2 months and risk not getting the deal)

ANy help/suggestions?