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OK I have a 100% original stock 92 FXR. The breather hose comes from the right side of the case at the oil pump and vents to the atmosphere a little ahead of the swingarm. I have seen other 92's do the same thing. I have read articles that say head breathers started in 92 and others say 93. I just had the aircleaner assembly off and fired it up. Air was coming out and pulling back in at what would be the breather bolt holes. The 92 has the larger bolts like a head breather but they are solid. Am I just short the umbrella valves, correct bolts and A/C backplate that woud work correctly? 92 sure was a bas_ard year.
What have I got here???
 

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Did you convert this yet? If not it sounds like you can convert is over. I forget where, but I seem to remember reading that some guys would actually run both the crank case breather and head breather setup.
 

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My 92 softy was a bottom breather, I was always led to believe that 93 was the first year for head breathers.
 

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I could see the moco having a mix bag of parts on a crossover year. If the bolt holes are big enough for the banjo breathers then I would guess those heads could convert. Does anyone know if pre-head breathing heads can be converted into top breathers? I mean is it just a through hole or some elaborate passage way to vent through the heads?
 

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its not he heads that determin the top or bottom breathing its the engine block having the lower vent for the breather valve - 1992 in all the parts books it is a top breather - it was for emissions, sending all the air from the crankcase to the air filter so it could be trapped internally in the engine --
92 up engine blocks might or might not have the vent plug behind the oil pump to be able to do that conversion - when you buy an after market block like S&S they recomend converting to the bottom breathing - it will help keeping the motor from leaking and will produce a better power cerv < on a dyno you COULD see a speed of torque increase by switching to bottom breathing -- jz
 

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Cool, I guess that makes sense then. You need the air to be routed to the top. So to Cranky's question if he's feeling pressure coming out of the banjo bolt hole then he may be feeling just the valve train, and he needs to pull the oil pump to check for sure? (Yeah, I'm hijacking his thread, but I have a '91 and I want to know how this works and hopefully answer his question too :) )
 

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Cool, I guess that makes sense then. You need the air to be routed to the top. So to Cranky's question if he's feeling pressure coming out of the banjo bolt hole then he may be feeling just the valve train, and he needs to pull the oil pump to check for sure? (Yeah, I'm hijacking his thread, but I have a '91 and I want to know how this works and hopefully answer his question too :) )
breather valve part number is 25300 - 36 < 1936 first year used and is the first one to be put in a harley motor, they had the same design with the air exiting the engine block bottom till 1992 sort of dont beat me i am trying to explain with out an hour of reading, in 1992 they changed the internals of the cylinder heads to vent only through the head ports with the banjos and not the engine block bottom -- because of emissions they sent the air to the air filter so it did not escape into the sounding air, like the bottom breather does -- i hope that answers your question -- jz
 

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Your breather hose originally was routed to the air cleaner backing plate.

But it was re routed down to the frame, just as most of us have done.

Your bike originally came set up as a bottom breather. The `92 heads are top breather castings, but there were inserts in the heads to block the openings where the backing plate mounts. If you remove those inserts, you can use the larger size bolts like the head breathers use.

Your heads did not come with umbrella valves installed.

I think reason that the factory went with the head breather was to eliminate the external hose that we could vent to the atmosphere away from the intake. It was an attempt to make it difficult to re route the breather, not to make the breather system better.
 

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Discussion Starter #9 (Edited)
Check your parts books, 92 A/C backing plate has no provision for a breather hose or for 93 up head venting.
92 is a bastard year, the case vents to the atmosphere below the frame. The cases are definitely bottom breather parts. The head part numbers are all for top breathers. Solid bolts and the absence of umbrella valves and correct A/C backing plate are the limiting factors for head breathing.
In 93 there was an addendum to the 92 FSM showing the head breathing service. These addendum a are rare but I do have one. I also have the FSM and FPM's for 91, 92 and 93, 94.
I prefer the bottom breather since there is no oil down the right side after a highway run.
When I do the cam and bearing I have a breather valve I modified per Donny Petersons directions in his book.

Enough rambling. Bye for now




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Well, Thanks for the info guys. It looks like next month my 91 is going to get a top end job done to it. I'll have to look up the Donny Petersons breather valve modification and see if I should change anything while I'm in there.
 

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Check your parts books, 92 A/C backing plate has no provision for a breather hose or for 93 up head venting.
92 is a bastard year, the case vents to the atmosphere below the frame. The cases are definitely bottom breather parts.
Enough rambling. Bye for now




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`92 backing plate (OEM) most certainly does have a provision for the breather hose.

The breather hose on all models in `92 were routed to the intake , not vented to the atmosphere.

`92 a bastard year? Not by a long shot. `92 is easy...

Start looking for clutch and transmission parts for an `84 and you will know what a bastard year is...
 

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Hi guys, I have a '92 softail and I'm having too much oil leaking from bottom breather hose. Since some weeks ago I had to replace a pushrod I bought a gasket kit including all gasket for two heads, also with the umbrella valves. So, I installed also the umbrella valves when I closed the heads (that weren't installed originally by MoCo in '92) and I'm planning to close the bottom breath hose and to try to top breath to see if oil leaking will go better. To do that I need proper banjo bolts and fittings, but I saw solid bolts installed on my heads are 5-16/24 and I can't find anywhere banjo bolts of this size, the standard size is bigger I think. Can anybody help me?

Ps later I will try also to open the cam Cover and to apply the indications by Donny Petersen on his book about timing of breather valve to see if this solves.
 

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Discussion Starter #16
If this ain’t a blast from the past. I remember making this post. My FXR is long gone though. Leg was getting to unstable to hold up two wheels so I’m on 3 now. I do have a 91, 92 Softail FSM I’d let go. Some other stuff too.
 

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Yes I replied to a discussion very old, but I'm sure a lot of people who love oldies like me are still following this website and this topic ;)
Sorry for your FXR, but I'm happy to read you're still on the road!
 

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Unless you get top breather heads (93on) do not plug the breather from the cases. I repeat DO NOT PLUG BREATHER HOSE!!!

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Hi Misterfredy, thank for your reply.
I didn't mention that my heads are already for top breathing, if I unplug the solid bolts in the head I feel air coming out. Then, when I dismounted Rocker covers to change pushrods I verified that there is a passage behind those bolts through heads.
In '92 engine came out still bottom breathing but heads were yet ready for top breathing
 

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read section 3,, the first dozen or so pages,, so you understand how the breather and scavage oil systems function... before starting your project...
 
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