Author Topic: Case breather convert to head breather  (Read 516 times)

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Offline 91 evo

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Case breather convert to head breather
« on: May 31, 2018, 09:00:25 PM »
I have a 91 Evo and it's constantly spitting oil. In the bike it has half a 91 and half 93 flywheel. I changed the nose cone to a 93 so that it would fit the 93 pinion shaft, gears, and bolt. I'm now having a constant leak out if the breather hose that comes out of the case. I know the 93 is a head breather and that's why I'm getting the leak.

How do I change to a head breather to match the nose cone?
Any way to reroute the oil line to make it stop?
Any other suggestions?

Offline Riverside Joe

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Re: Case breather convert to head breather
« Reply #1 on: June 01, 2018, 05:31:39 AM »
Never done this (or considered it), but I'd say the heads and covers need to be changed to accommodate the reed valves and passages to vent to the a/c. This would be a start I would think about in converting over to a head-breather. I would want to consider why your oil pump is not scavenging oil also. If the pump is worn, the dripping oil issue may be present even with the heads changed over. The new cone may not have the passages to allow a weak pump to scavenge effectively. One of the more experienced pro's here can give more depth, but these are my first things to consider. Good luck---------RJ
« Last Edit: June 01, 2018, 05:55:24 AM by Riverside Joe »
RFFR

Offline Mule

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Re: Case breather convert to head breather
« Reply #2 on: June 01, 2018, 07:24:05 AM »
You have a head breather cam cover on a case breather set up, sounds like that could be your problem... late 92 was the change. You need to change the heads to breath out of the top.

Offline Scott P

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Re: Case breather convert to head breather
« Reply #3 on: June 01, 2018, 08:07:04 AM »
Heads need to be machined, breather head hardware, and breather head rocker cover(s).
Otto Knowbetter sez, "Even a fish wouldn't get caught if he kept his mouth shut"

Offline 91 evo

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Re: Case breather convert to head breather
« Reply #4 on: June 01, 2018, 03:55:30 PM »
Because of the the way the cases are set up, will I get to much oil in the cases through the metal dowel if I covert to head breather?

Offline Mule

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Re: Case breather convert to head breather
« Reply #5 on: June 01, 2018, 04:10:12 PM »
Last year I built a 3 13/16 std cased ,axtell cylinders evo engine, it was a case breather case with late evo head breather heads. I used an early Jim's case breather two piece cam cover with the breather heads and umbrella valves. Sold that motor to a guy in Northern California ,he installed it in a 96 softail, no oil carry over issues at all and runs like the famed striped ape.  It breathed out of the top and bottom. If you are using the case breather, I think you need the early cam cover...

Offline Mule

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Re: Case breather convert to head breather
« Reply #6 on: June 01, 2018, 04:13:10 PM »

Offline Riverside Joe

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Re: Case breather convert to head breather
« Reply #7 on: June 01, 2018, 05:28:16 PM »
You could pull the cover and look at the differences between the covers, and re-verify the breather timing for piece of mind. The vent is supposed to allow air to move back n forth. The oil mist is going to dribble any where you put it. Alot of misting would tell me alot more oil is accumulating some where, and the pump is not pulling it out fast enough. "will I get to much oil in the cases through the metal dowel" metal dowel?-------------------------------RJ
RFFR

Offline 91 evo

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Re: Case breather convert to head breather
« Reply #8 on: June 01, 2018, 06:35:30 PM »
I'm going to modify the heads and get new rocker boxes then plug the bottom breather hole in the case. I'll let you guys know if it works.

Offline JW113

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Re: Case breather convert to head breather
« Reply #9 on: June 01, 2018, 06:55:16 PM »
The '93 nose cone does not have the oil baffle chamber to separate the oil mist from the air before getting passed out the breather tube. So the combination that you have is bound to not work. You can fork over coin to convert the heads/rocker boxes to '93+, but an alternate approach would be to have your '91 nose cone machined to accept the '93 pinion shaft.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Offline Burnout

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Re: Case breather convert to head breather
« Reply #10 on: June 03, 2018, 05:29:16 PM »
I don't think you can just switch the cover to get a case breather.
Aren't the cam cover gaskets different?
I know if you have the wrong gasket on it, it will be a slobbery beyotch
Or,
Back off the spark timing so the rings can seal if the factory setup won't hold oil.
Or fix whatever else is wrong causing the ring seal problem.
If you try to re-engineer stuff especially if something else is the cause you will just wind up keeping oil in stock (by the case).

Got a leakdown tester? Got a bore scope? Does your oil quickly get black?
They don't call me Ironhead Rick just because I'm "hard headed"

Offline turboprop

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Re: Case breather convert to head breather
« Reply #11 on: June 03, 2018, 07:00:43 PM »
Just stop. Converting a case breather to head breathing is as simple as switching out the heads (or having the early heads machined) and using the later style rocker boxes and AC hardware. Simply use the correct cam cover and gasket for whatever year the case is. Done. Amazed at the ongoing discussion over this and all the wrong info being repeated here.

Offline JW113

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Re: Case breather convert to head breather
« Reply #12 on: June 04, 2018, 05:24:01 AM »
Rick, I've done just that. Put a set of '94 flywheels in my '91. Simple operation to machine the nose cone to clear the pinion shaft.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Offline 91 evo

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Re: Case breather convert to head breather
« Reply #13 on: June 22, 2018, 04:12:43 PM »
Got it running and no issue. I ended up drilling out the head and putting 93 and later rocker boxes on.

Offline turboprop

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Re: Case breather convert to head breather
« Reply #14 on: June 22, 2018, 06:44:40 PM »
Got it running and no issue. I ended up drilling out the head and putting 93 and later rocker boxes on.

Yep. Its that easy.