Harley 45 Replace Breather Valve In Gear Cover
Article by Mark Trotta
On the back bottom of every Flathead 45 gear cover, there is a small, round breather valve, commonly called a flutter valve.
These little one-way valves are often overlooked during an engine overhaul.
Breather Valve Operation
When operating properly, they open by vacuum on upstroke of the pistons, sucking some oil out of the cam chest through a passageway in the right crankcase.
Why They Go Bad
Through no fault of their own, from lack of oil changes or when left sitting for long periods of time, they can and do clog up. And since the Motor Company stopped producing these motors in 1973, it may well be over 50 years old!
When clogged, engine vacuum can't pull oil through it. With nowhere else to go, oil begins to drip from the cam chest out of the relief pipe.
Pictured: Relief pipe oil leak on author's 1961 Servi-car.
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Gear Cover Removal
Replacing a clogged breather valve requires removing the gear cover, which entails taking off the right floorboard, ignition timer, generator, oil feed pump, steel oil lines and both exhaust pipes.
Read: Remove and Install Harley 45 Gear Cover
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Remove Breather Valve From Gear Cover
Because it is staked from the factory, it needs to be pushed out from the inside.
Here, I'm using a 2" metal clamp, 1/2" socket, and an 8-32 machine screw with the head cut off. There is just enough room in the relief pipe cavity to fit the headless 8-32 screw (5/8" length).
Insert the screw into the cavity against the back of the valve, with the 1/2" socket on the outside of the gear cover.
By slowly tightening the clamp, the flutter valve will pop out of it's factory-staked position.
You can try cleaning the old one by soaking it in brake parts cleaner, or buy a new one here.
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How To Test Breather Valve
The valve can be tested while still in the cover.
To check if it's working properly, place your mouth over the valve opening and blow into it. If you feel air coming through the other side, it needs to be cleaned or replaced.
Then try sucking air out. You should be able to suck air through it, but not blow air through it.
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Install Breather Valve In Gear Cover
You can easily install these backwards - make sure the larger hole faces out!
To double check, blow into it. Air should not go through it. When you suck on it, you should be able to pull air through it.
The old breather valve taken out of my 1961 Servi measured .04385" in diameter. The new valve measured .4405" in diameter. This made it a little harder to install.
You can try to drive it in with a small socket or bearing driver tool, but the problem with this method is the outer (finned) part of the cover is not flat, so you can't get a good solid hit on it. Plus you may damage the valve.
The best and easiest way to install is with a shop press.
If yours goes in easily, to insure it doesn't work it's way out, lightly stake the case around the valve in four places with a hammer and punch.
Install cover with new new gasket. Sealant is not necessary. Install and tighten ten screws in a star pattern.
Cam Cover Gasket for Harley 45 Flathead replaces OEM 25226-37
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