*PISTON RING SEATING - THE "DRY CYLINDER" METHOD by Tom Cutter*

     The "Dry cylinder " method does not mean just don't oil anything. It
ESSENTIALLY means don't flood everything with copious amounts of oil on
assembly.

     Here's how I do it. My customers can tell you whether it works...

     I Hone and then thoroughly wash the cylinders and pistons, rings,
etc. with Safety-Kleen solvent, then finish with hot soapy water, then a
hot water rinse. Everything is blown dry with compressed air, and left in
the sun to dry. (Freshly-Nikasealed cylinders do not need to be re-honed.)

     I use an oily (WD-40 or clean motor oil) rag to lightly wipe the
cylinder walls. This cleans any residual honing grit from the crosshatch,
prevents surface rust, and makes everything slide together well. I want the
surface just barely oily.

     I assemble the rings onto the pistons, then install the pistons into
the bottom of the cylinders until just the skirts and wristpin hole is
showing. Install the rear wristpin circlip if you took it out (I usually
don't.) Then slide the cylinder onto the studs, and line up the connecting
rod wristpin holes. I put a few drops of oil on my finger and oil the
wristpin and bores, then install the pin and clip. If the pin is tight, I
heat the piston a bit with a heat gun. If the pin is still tight, I pull
the cylinder back off and clean the burrs in the pin bore. Once the piston
pin is installed and the clip is secure (put a rag in the crankcase hole to
keep the pin from flying in there,) I'm ready to finish installing the
cylinder.

     I apply a thin coat of Suzuki 1207B sealant onto the cylinder base
sealing surface and both sides of the aluminum base gasket (if the bike
uses gaskets) as well as onto the crankcase surface. The film must be very
thin, and evenly applied.

     Now I apply two or three DROPS of clean motor oil to each side of
the piston skirt, top and bottom, smearing it on evenly. Don't let any oil
drip on the sealant.

     I lightly oil the pushrod tube rubbers on the outside so they can
slide into position.

     Now I push the cylinder fully home, install the head gasket so the
writing faces me, and install the heads and rocker arms without delay.
Torque the heads in a progressive 3-step sequence, and adjust the valves.
Place a powerful fan in front of the motor to prevent bluing of the
exhaust. Start the motor, rev it to 2500-3000 RPM and hold it there for
about 30-45 seconds. Shut it OFF (no idling) and don my helmet and gloves,
jump on and take a brisk 5-10 mile ride.

     When I return, I shut off the motor, prep the carburetor adjusting
tools, place the fan in front of the engine again, start it up, adjust the
carburetors and shut it off.

     Let it cool overnight, recheck the valve clearances and send it off
to the owner, with an advice to return in 600-800 miles for another valve
check.

     I’ve done a lot of BMW motors that way, and they ALL run well. Some
have been apart repeatedly (racebikes and my street bike) and show NO sign
of cylinder damage.)

©Tom Cutter 2014