valve problems

[camocj5]

I have a valve that I just acquired. It shoots 300+ for the first shot then it keeps dropping 50-75 fps for about 5 or 6 shots then back to 300+. What do I need to do? Any advice from you guys would be greatly appreciated.
Thanks
Shane

[tdogreb]

what type valve is it? classic,rt,xvalve,emag?

[camocj5]

Sorry, I should of included that. Its a classic valve.

[NeilS300]

Try cleaning out the regulator piston.

[Enemy]

check the reg piston seat tooo had lots of inconsistancy took that out reset it better and that brought me to
+/-5fps so i would defenitly take a look at that too. if not that then make sure you reg spring pack as plenty of lube in it