Last Saturday a friend and I changed the cam chain tensioner on his 2001 GS. Enjoy the photo journal.
To begin, here is some information that will address a few common preliminary concerns.
The method of replacing the cam chain tensioner described here does not require a throttle cable readjustment.
The engine crankshaft does not have to be at TDC or BDC or any particular orientation.
But, the 'tension side' of the cam chain should be tight. And the 'slack side' of the cam chain should be slack. This only means that before you start the job, rotate the crankshaft a small amount in the direction it normally turns.
Turning the crankshaft by hand is easy to do. Put the bike on the centerstand and put the gearbox in top gear. Using your hands, rotate/bump the wheel forward until you feel some bit of engine compression, then stop.
Good. The cam chain slack is now on the tensioner side. The chain slack is on the tensioner side when the engine is running.
The chain slack is normally on the tensioner side. But, sometimes when the engine stops, the crankshaft rotates backward a small amount, 'slackening' the tension side. Turning the crankshaft a small amount returns the chain slack to the tensioner side.
The original tensioner has a spring. And when unscrewing the tensioner, when the last thread is reached, the spring will push the tensioner body up from the bore.
The spring tension is gentle. Gentle as in about 2 pounds. About twice the spring tension of a retractable pen.
Also, no parts can fly across the room. The tensioner body will lightly contact the bottom side of the control arm, and stop. At that point the tensioner body will be only 2/3 of the way out of the bore. That is as far as it can go under its own power.
Getting the tensioner the rest of the way out of the bore will probably consume the greatest percentage of the total job time. It would be nice if the tensioner 'sprang' out of the bore, that would eliminate the only time consuming part of the job.
No tensioner parts can fall into the engine from the tensioner bore. Not even if it falls in 'just the right way'.
At some point your hands will be working in a limited space while fiddling around trying to get the tensioner spring out from under the tensioner body. Go at this with abandon, no tensioner parts can fall into the engine from the tensioner bore.
Here are the factory original PREVIOUS MODEL parts, and the FIRST EDITION UPGRADE MODEL parts as of Feb '05. The first upgrade model was priced over $200
Here are the factory ORIGINAL PARTS, and the CURRENT PARTS as of May '07. About $60 to $70.
Start by loosening these two intake tube clamps. Do not loosen the tube clamp that is located next to the cylinder head.
These steps are straightforward enough.
Your throttle body o-ring may look like it has stretched. This one looks pretty good. The o-ring absorbs hydrocarbon crankcase vapors and swells. If it has, the intake tube will tear the o-ring when slid back over the throttle body.
This phenomenon is identical to what happens to the o-rings on the fuel tank quick disconnects.
BMW O-ring p/n 13 54 1 341 797 ___ 52mm x 2mm ___ $3.10
Unplug the fuel injector electrical connector.
Remove the fuel line retainer spring clip.
Remove the two fuel line screws.
Pop off the injector fuel line.
Look at that, the o-ring stayed with the fuel line end cup.
Pull out the fuel injector.
Put the o-ring back on the injector.
Disconnect the Throttle Position Sensor (TPS) electrical connector.
Cut the zip-tie for the TPS cable.
Remove the throttle body ground lead.
Remove the two intake manifold flange screws.
Here is a look at the end of the intake manifold 'flange'.
You will need another special tool.
Make a hangar out of the wire and suspend the throttle body and intake manifold out of the way.
Without stopping to stage photos, it takes about 10 minutes to get to this point.
17mm combination wrench works well enough to loosen the tensioner.
Get you a big paperclip and make one of these.
Use the small hook to grab the top, or near the top, of the spring
First pull down on the spring, and then out from under the tensioner body.
Here is the spring removal sequence. You may get lucky and get it the first time.
Use the other end of the paper clip tool to retrieve the piston. Make the paperclip 'vee' large enough so that it is a force fit and will grasp the piston from the inside.
Old parts going to the archive.
Now it is time to install the new tensioner. Start by dropping the piston into the cylinder bore. (There is no picture of this step.)
The large piston can be dropped into the bore . . . plunk. The old piston did not fall into the engine, and neither will the new one. Just drop it in.
The new components fit together like this. It is easier to drop the piston into the cylinder bore that to try to install them while mated.
Slam dunk. Remember, the top of the tensioner body must go up and behind the suspension arm before it can be guided into the bore.
These casting marks are for component alignment.
Rotate the fuel injector body out of the way, and snap on the retaining clip.
The fuel injector retaining clip must slide on smoothly with a nice 'detent click' when fully seated. If the retaining clip does not slide on smoothly, the problem is the injector is not pushed far enough into the fuel cap.
Rotate the injector body so that it is in front of the retaining clip.
Plug in the electrical connector. When oriented correctly, the electrical connector blocks the injector retaining clip.
Job complete. A-a-a-h-h - h - h. The first start up was nearly silent.
Thanks for the props everyone. Happy wrenching.