It is not uncommon to have more
crankcase pressure when engines are
modified. The engine demands increased
venting. In most cases the pressure is
minimal and just enough to be
aggravating. In the case of the 1999 –
2006 Twin Cam 88 Harley Davidson
engines, this is easily eliminated by
installing a Doherty Machine MYSTFREE
The kit comes with all parts needed and
easy to follow instructions to replace
the factory breathers. If you work on
your motorcycle and have some hand tools
and basic knowledge you should be able
to do this at home quite easily.
Rogue’s dresser. Not many see the miles
this one does.
I started by removing the seat and the
battery ground cable.
The instructions say you can raise the
gas tank and not have to remove it. I
opted to drain and remove it for more
room and also better light for these
Front rocker removed.
Remove the six bolts securing the rocker
box cover using a 7/16 box wrench, 3/16
Allen wrench or 6529 Kastar Rocker Box
Wrench. Discard the old gasket and then
remove the two bolts from the stock
breather with a 3/8 socket. Clean the
There’s the stock breather, we’re going
Install the copper gasket, lower unit,
paper gasket, and the top plate. Use a
little blue Locktite on bolt threads and
torque to 90-inch LBS.
Stock breather removed.
Install the new rocker box gasket and
tighten bolts in sequence shown in the
shop manual. Torque to 180-215 Inch LBS.
Installing the lower plate of the new
Repeat for other cylinder, re-install
gas tank, connect battery ground,
install seat, start engine and check for
Top Doherty cap installed.
There were none, so I went for a ride.
When I returned there was no misting or
fluid creeping out the breather.
Taking the torque wrench to the breather
I wish every job was this easy and
worked as well. Give the MYSTFREE a try.
I am sure you will be happy you did.