I agree, it needs carb o-rings. You can get them from Tower Hobbies...They are easy to change and I'll bet you will find the current o-rings hard and brittle once you take it apart...

It's a standard RF-P (not a Hanno) right?? The Hanno uses a different carb (6P) where as the standard RF-P uses the Type 86 carb...Does it have four nipples on the pump or just two??

edit:
attached is a PDF copy of the manual for the Type 86 carb which has the o-ring locations shown...

The o-ring part numbers are:
[link=http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=27881800&search=Go]27881800[/link]
[link=http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=27881810&search=Go]27881810[/link]
[link=http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=27881820&search=Go]27881820[/link]
[link=http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=24981837&search=Go]24981837[/link]
(If you click on each of the numbers above it will take you to the Tower's web page for that part...Order one package of each...)

Also...To avoid any confusion...The OS RF-P does not require a check valve...