Assembling the 65 motor. I've recently had two Ironhead mechanics tell me to leave the breather valve screen (25276-52) out when assembling the oil pump, as it tends to cause problems.

There are two screens. This is the one I'm talking about.



Pinion? Patrick? Anyone have any experience with this? Please weigh in.

 

I left mine out when I just recently rebuilt mine. If you have pulled the machine apart and know that the oil lines are cleared, the crank is clean, the tank is clean, and you know your not using any gasket sealant then I say you don't need it.

Others will disagree I'm sure, but the chances of something that large going through your system is unlikely.

 

I have no idea what 'problems' could be caused by using the breather screen. Ask those guys what they are referring to. See if they can provide an answer that makes sense. I would be surprised.

Myself, I always install the breather screen. I would no more leave it off than I would leave the scavenger section screen off. Both screens are there to prevent metal chunks from entering the oil pump.
To leave these screens off is to invite disaster in my opinion.
If a gear tooth chips off or a spacer washer breaks (unlikely, I know) and pieces get to the pump internals, then the game is over.
I recommend you use the screen............ pg

 

I built several Sportster motors years ago (1970-1975), one being a fuel dragster motor,I had several friends that had been building Sportster engines since the mid sixties. Leaving any screen out was NEVER discussed, What does leaving it out get you? As usual, PINION knows what he is talking about better listen!

 

im not trying to hijack your thread moonwolf but just wanted to ask a simple question----does that go inbetween the oil pump and the engine or is that located inside the oil pump?i am guessing it goes inbetween....i do not remember seeing any screen on/in my old one and nor did my new one come with it and i would like to have them.i have an 81 xls i am assuming it calls for it as well.seems like it would be a long shot that it would be needed but if you did not, not only would you have that problem(whatever broke) now you possible have a broken oil pump and a toasted engine....i suppose somthing like that might have a tendency to clogging up over time especially if oil is not changed often, i dunno. i would like to know what the ironhead mechanics reason for not putting it on as well.

is ther any chance of that screen being sucked into the oil pump?

 

That screen does not occur anywhere in the 79 to 85 parts book or FM, so i would assume that it applies to only earlier models.

 

Thanks, Pinion. That was my inclination as well. I was just trying to pin down the rumor, trying to find out if anyone had heard anything about this.

 

i wonder what changed to make them not put it in the later models???

 

Yes, this screen is only in the early model pumps. There is a another screen outside the pump.

On late model Sportsters, apparently riders often remove the screen on the outside of the pump because it interferes with scavaging. This is hearsay, of course, as I am strictly an old bike guy. That may have been where the idea of leaving the internal screen out came from. I'd like to get to the bottom of this, though, so if anyone has heard any reason why the screen I'm referring to should be left out, I'd like to hear it.

 

The screen you are talking about is a loose screen that you need to hold in place with grease as you install the oil pump. This screen is for the breather.
The other screen is a round and slightly conical screen held in place with a pin. This screen is for the scavenger section of the pump. (Return of oil to the tank)

As for the later models not having the breather screen.......? My best guess is because the oil pump was redesigned sometime around 1977 wasn't it? Perhaps the screen was eliminated then?
I do not know that for a fact, so maybe someone more familiar with models later than 1976 can weigh in here......... pg