I recently stripped my 140 rx and am now putting it back together complete with stainless steel bearings. I also pulled the pump apart tp see if it was clogged with any gunk, which all seemed fine, but silly me did`nt take much notice of the orientation of the diaphram spring inside, it can either sit with the large side facing towards the pump which is how i think its meant to fit?? or it can sit the other way with the larger side on the plastic washer which mounts flush with the same metal plate.

Can anyone offer some advice on the way it should sit? I would hate to damage the pump by fitting the spring upside down [&o]

I've always heard dont do anything to the pump, not that helps you now You should be able to download a PDF manual from the os website.

No taking the pump apart is ok.. what you most likely heard was not to touch the adjustment on the backplate, this is the pressure and flow adjustment of the pump, i have mine apart and aint anything special inside, its just a diaphram pump, the only thing is im just not sure exactly ahich way the internal spring is meant to face...someone out their has to know???

Rogue Rover,
Had a similar problem when fitting an OS 140 RX pump to my OS 160 FX. I reinstalled the spring with the larger diameter coil against the diaphragm and have done about 200 flights since with no problems.
Cheers,
CW

Ok thats grat to hear you are having luck with the spring, but the design of the pump chamber to me suggests otherwise... on the opposite side to the diaphram mechanism is a small metal plate which just happens to have the same size seating space as the dia. of the larger side of the spring.. it firs in easy and for assembly is easily secured with a small amount of oil to keep it located while the pump screws are put in place.. ill give this a go and see how things go.. given the design of the plastic diaphram washer the spring pushes against, i think i have made the right choice.. will let you know ..

Happy flying

Here is two pictures i took when I cleaned my pump some years ago. They show the correct orientation of the spring.

Dude.. you are a ledgend!!

Thanks for posting the pics. I suspected that was the right orientation just from the design of the housing.

Do you still fly with the 140's ?

Cheers