Web service intermittent slow response time

[sachinkendale]

I have a web service developed in .net 1.1 and hosted in IIS 6 and using own application pool. Web service reponse is a xml. XML file can get as large as 2-3 megs.
Most of the times it takes less than 10 seconds to return response but sometimes it takes 60-80 seconds. I thought large XML file might be causing this delay but IIS log contradicts that.

Following are IIS settings,

Application pool set to recyle evey 25 hours
http compression settings are disabled in IIS.

Any ideas why this might happen?

Thanks,
sachin