R Bike (Air-cooled) Valve Job

Last February my purple 1991 R100RT rolled over 100K as it rolled, coughing, missing, and wheezing into my garage. It was raining out and I had just read San Jose BMW/CC Products ad for their valve job packages that said "The off season is here; send us your heads". So I figured now is the perfect time to do a job that I had been putting off for almost a year. As any owner of an air-cooled boxer knows, your valves are a weak link with unleaded fuel. The valves require constant attention with adjustments every 5000 miles. For me this turned out to be a task that came around every 4-6 weeks. (Hilary would say "Oh no, not the valves again" as I spent the next couple of hours in the garage.)

If your boxer is experiencing premature valve closure, and has over 60K on the clock, you might consider what is called a leak-down test. If you don't have the tool, your dealer can do it for you very easily. A leak-down test will pressurize the cylinder, and over a period of time determine the sealing quality of the valves. If yours turn out to be as bad as mine were you might want to think about a valve job.

This is my third valve job on three different boxers. I am not an expert, but the following steps have worked for me in the past:

Disassembly:

Remove the carburetor, spark plug & wire, lower fairing (if RS or RT), exhaust gas recirculating tube, valve cover, and exhaust nut and pipe (use the proper exhaust nut wrench). Loosen the head nuts, two on the 6 and 12 o'clock position and the four on the rocker shaft supports. Remove the rocker arms, rockers, and supports with all the parts carefully and set them in a clean place. If the head does not want to slip off easily, rap around the gasket split line with a plastic or rubber tipped hammer. Remove the head and old gasket.

While you have the heads off, and since you have broken the crankcase to cylinder seal, slide the cylinders off the pistons, being careful to cushion the piston and rings from the head studs.

Head Work:

I bundled up the heads and headed to CC Products where I found out that everyone else had read the same article about bringing their heads in during the wintertime. Great plan, I had to accept the fact that it would take six to eight weeks to recondition the heads. Kurt was very helpful and disassembled the valves from the head while I waited. Upon inspection we found what I had suspected, both exhaust valves were "tuliped" worn to a razor edge with little cracks around the circumference. The intake valves were OK and could be reused.

Clean up & Inspect:

While the heads are at the shop, clean all the parts with solvent and scrape any gasket cement from mating surfaces. Inspect all parts. Check the cylinder for any unusual wear, scoring, pitting or ridges. Those of you who have the newer cylinders without steel liners will probably not see any wear; mine still had the honing marks visible. When you go to the shop to pick up the heads, pick up new head gaskets, push rod tube seals, a tube of sealant for the base seal (I used a product called Dirko), valve cover gaskets and any other worn or unusable parts.

Reassembly:

Last off, first on, remember that! Install the new push rod tube seals and check to see that they are installed with the large side facing down. Put a thin layer of sealant (more is not better) on the mating surfaces of the crankcase and cylinder. Two o-rings that go on the upper studs should be installed on the cylinder so you do not pinch them as the cylinder assembles. Check the position of the ring gaps, make sure none are aligned, and install the cylinder using a ring compressor (I use a large hose clamp).

Install the head gasket correctly; make sure that the holes for the push rods are clear. Slide the head over the studs and just snug up the two nuts at 6 and 12 o'clock. Don't forget to insert the push rods down the tubes into the sockets of the lifters. The rocker arm shafts and nuts go on and you are ready to torque the head. The valve adjusting section in your rider's manual will show you the correct torque and pattern of tightening the head nuts. Squeeze the rocker arm supports together as you tighten the head nuts for proper clearance. The rocker shaft end play should be close to zero, just so the rocker rotates with a snug feel, without binding. Adjust the valves on the loose side for break-in (0.010 exhaust, 0.006 intake) and reinstall the valve covers.

Reinstall everything else: carburetors, exhaust system (use no-seize on exhaust nut and spark plugs) and make a thorough check around the bike to see that all parts are installed correctly and bolts and nuts properly torqued. Now is not the time to find two push rods lying under a rag by your toolbox!

Road test:

Now is the magical moment, you turn on the ignition and... nothing! You have neglected to keep the battery charged while awaiting parts. Success at last, the beast fires up and roars like a new machine. The smells of cooking gaskets and oil on the exhaust pipe fill the air as the engine warms up. As I pull out of my driveway I notice right away the improved torque and throttle response. At stoplights the engine idles very smoothly and does not die as before. It is amazing how much deterioration in power we get used to when we drive a bike everyday. An engine gets tired very slowly.

Ride your bike for 50 miles, then park it overnight and check the valve gap cold. Check it again at 250 miles and at 500. After 500 miles adjust valves to 0.008 exhaust, 0.004 intake and adjust your carburetors with the engine warm.

Now the engine is ready to go another 100K, but the real question is am I? The lure of the shiny R1100RT has taken some of the glitter off of the poor R100RT.

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