The engine came with the stock 8.2:1 compression pistons. But the early RS motors came with high compression 9.5:1 pistons. The bike has 83,000+ miles on it. So I decided to install new high compression pistons. Tom Cutter at Rubber Chicken Racing Garage, told me due to the very tight piston clearances in the Nikasil cylinders and the amount of variation in piston diameter with the new pistons, the best way to proceed is to replate the cylinders with Nikasil and hone them to match the pistons to ensure proper clearance. So, I send him the new pistons, rings, wrist pins and old cylinders for this work to be done. I also had him vapor hone the cylinders to refinish them to the factory patina.

Refinished Cylinders with New Push Rod Tubes

The other work needed was to the heads. When I tested them, the valves were leaking. So I sent the heads to Randy Long, at Long’s Mechanical Services, who is a well respected head rebuilder, for his opinion. We decided to replace the exhaust valves, all the exhaust guides, springs and keepers. I had him machine the heads for dual plugs. I have dual plug heads on two airhead bikes and I like the improved gas mileage. Randy milled the valve cover mating surfaces so they are flat and bead blasted the heads so they look brand new.

Randy Long’s Rebuilt Heads

Rebuilt Head with New Exhaust Valve and Dual Plug Conversion (Note Two Spark Plug Holes

Here is what I ended up with. The red tape indicates things I need to do before first engine start: install new spark plugs and put oil in the engine. The rags protect the heads from getting anything inside from the intake and exhaust ports.

Red Tape Means Not Ready Yet

All Done

Here is written documentation of the procedure:

• 11 BMW 1983 R100RS Install Top End

And here is a video of the procedure.

VIDEO: 1983 BMW R100RS Install Engine Top End

I had the connecting rods inspected, reconditioned, and new wrist pin bushings installed by Tom Cutter at Rubber Chicken Racing Garage.

Connecting Rod Parts

I did that since this engine has over 83,000 miles on it. As Tom said about the life of connecting rods:

“Metal parts get deformed when they get traumatized by 270 TRILLION
combustion cycles (4500 RPM, 60 MPH, 100,000 miles= 270 and more zeroes
than I have left in my computer.) Just a lotta lotta little taps will make
metal flow. In the case of connecting rods, that becomes manifested in
misaligned and ovalled bearing bores. Wristpins rock, both radially as well
as axially, which deforms the small-end bushings. That stuff needs
attention on a high-mileage engine reconditioning.”

Here is how I install the reconditioned rods and the cam followers.

• 11 BMW 1983 R100RS Install Connecting Rods & Cam Followers

And here is a short video summarizing the procedure.

VIDEO: 1983 R100RS Install Connecting Rods & Cam Followers

I decided to install 9.5:1 high compression pistons used in the earlier RS engines instead of the original 8.2:1 pistons used in the 1983 RS motor. Due to variability in piston diameter and the tight clearance required with Nikasil cylinders, the advice of Tom Cutter at Rubber Chicken Racing Garage is to replate the cylinders with Nikasil and hone them so they provide the optimal clearance with the new pistons. So I sent the cylinders and new pistons to him to have this done, but before I did, I removed the push rod tubes and the head studs from the cylinders. You can see how I do that here:

• 11 BMW 1983 R100RS Remove Push Rod Tubes & Cylinder Studs

Now I am ready to install new stainless steel push rod tubes and the original head studs into the cylinders.

Here is a link to the write-up.

• 11 BMW 1983 R100RS Install Push Rod Tubes & Head Studs

And a short video summarizing the procedure.

VIDEO: 1983 BMW R100RS Install Push Rod Tubes & Head Studs

I always mark the installation of the engine back into the frame as a happy milestone. At last, entropy is being reduced along with the parts pile in the corner.

Here is a short video showing how I install the engine.

VIDEO: 1983 BMW R100RS Install The Engine In The Frame

And some pictures.

Frame Back From Powder Coating

Frame Rails Protected with Foam Packing Wrap

Engine Ready To Pickup And Install

Engine Slides Into Frame At The Rear

Front & Rear Engine Mounting Rods Installed

Engine & Frame Strapped to Motorcycle Stand

It’s time to work on the bottom of the engine.

Engine Block Securely Mounted On Harbor Freight Motorcycle Stand

I replaced the oil pan and the oil pump suction flange gaskets.

New Gaskets-Green Is Oil Pump Suction Flange Gasket

Along the way, I checked the oil pan to see if the mating surface was flat.  It was not, so I sanded it and now it’s flat. That should go a long way to ensure the new pan gasket does not leak.

Checking For Uneven Mating Surface On Oil Pan

The gaskets I need are included in the EMC engine gasket kit. I’m also going to replace the oil pan bolts and wave washers with new stainless steel hardware I got in the bolt kit  from “The Bolt Guy” for the RT model since I’m converting the RS to an RT, not that RT pan bolts are different from RS ones.

To prevent the threads of the stainless steel bolts from galling in the aluminum bolt holes in the engine block, I apply anti-seize. However, it’s a lubricant. Since the recommended torque for the bolts is 6 FT-Lbs, which is quite low, if I torque the lubricated stainless steel bolts to that value, I stand a good chance of stripping the threads. So I reduce the torque by 20% to protect the threads.

For low torque like this, I always use my INCH pound torque wrench.

You can read about how I did the work here:

• 11 BMW 1983 R100RS Replace Oil Pan & Oil Pump Suction Flange Gaskets, Get Oil Pan Mating Surface Flat

And here is a short video summarizing the procedure.

VIDEO: 1983 BMW R100RS Replace Oil Pan & Oil Suction Flange Gaskets