Actually i found it myself ,after some googling and an awesome link
http://tech.avivo.si/2011/10/increase-maximum-request-length-for-wcf-rest-web-service-asp-net-4/[
^]
<bindings>
<webHttpBinding>
<binding name="ApiQuotaBinding" maxReceivedMessageSize="10485760"
maxBufferPoolSize="10485760" maxBufferSize="10485760" closeTimeout="00:03:00"
openTimeout="00:03:00" receiveTimeout="00:10:00" sendTimeout="00:03:00">
<readerQuotas maxDepth="32" maxStringContentLength="10485760"
maxArrayLength="10485760" maxBytesPerRead="10485760" />
<security mode="None" />
</binding>
</webHttpBinding>
</bindings>
----in the endpoint section make a reference to binding ApiQuotaBinding
<endpoint address="" bindingConfiguration="ApiQuotaBinding" binding="webHttpBinding"
contract="Avivo.Web.Services.IApiService" behaviorConfiguration="ApiBehavior" ></endpoint>