how can i setal bike purchase on name of firm

ITC not available for the Purchase of Bike...

You can book the total value as Asset head and Provide depreciation on the asset value as Depreciation rate...

Yes book as below Suppose your bike cost with GST 59000/-


Dr : Vehicle A/c. ... 50000
Dr .. Input A/c .. 9000
Cr......To Dealer A/c. .............59000/-

Now Reverse the ITC As per Sec 17(5)
Dr ... Vehicle A/c ..... 9000
Cr.... To Input A/c ....9000

Now charge the depreciation on whole Amount on 59000/-

Show the Above ITC debited & ITC credited in Your 3b , As because your GSTN is mention By dealer of bike in Bill (B2b)

depreciy on whole Amt or on net Amt 50000/-

You can Take ITC if full below conditions  otherwise can not take itc and book  gross invoice value( including GST) in a/c book to a/c fixed asset

1. resale bike

2. transport goods from one place to another