In my opinion Cenvat Credit of service Tax paid on serving and repairs done for cars and bikes cannot be availed.
as per rule 2(i) of CCR 2004, Input Service means:-
(i) used by a provider of taxable service for providing an output service; or
(ii) used by the manufacturer, whether directly or indirectly, in or in relation to the manufacture of final products and clearance of final products upto the place of removal,
(This clause has been amended vide Notification 10/2008 C.E. (N.T.) - dated 01-03-2008)
and includes services used in relation to setting up, modernization, renovation or repairs of a factory, premises of provider of output service or an office relating to such factory or premises, advertisement or sales promotion, market research, storage upto the place of removal, procurement of inputs, activities relating to business, such as accounting, auditing, financing, recruitment and quality control, coaching and training, computer networking, credit rating, share registry, and security, inward transportation of inputs or capital goods and outward transportation upto the place of removal;
Rule 2(I)(i) is applicable to service provider and Rule 2(I)(ii) is applicable to a manufacturer.
as the above mentioned is a service porvider and the mentioned service doesnot fall in the definationof Input Service hence it will not be eligible for Cenvat credit.