"Take the ideas of the masses and concentrate them, then go to the masses, persevere in the ideas and carry them through, so as to form correct ideas of leadership - such is the basic method of leadership."
"Some Questions Concerning Methods of Leadership" (June 1, 1943), Selected Works, Vol. III, p. 120.
Attach the front mounting ears to the steering stem.
The rear attaches to the brackets with the two rubber pads above the bracket and one underneath on each side. DO NOT OVER TIGHTEN!
It is a good idea to use new rubber gas line and hose clamps available at any auto parts store. Don't forget the cross-over pipe that runs under the frame. There are two little tubes that come out of each side of the gas tank at the bottom back. These have to be connected with a piece of hose.
Removal
If possible/practical drain all fuel from the tank into an approved/safe container before proceeding.
Underneath the tank and running underneath the frame's cross-over pipe there is a rubber tube connecting both sides of the tank (to keep the tank fuel level balanced). You will need to carefully remove one side of this so that you can...
Chang Jiangs do not come with a fuel filter installed. Adding one to the fuel line that connects the petcock to each carburetor is a very simple and a very smart thing to do. (Help Us: Add your knowledge here!) provide photo and links to suitable fuel filters
Carburetors
28mm carburetor used by M1, M1M, and M1S
Balancing / Tuning
The carbs have to be synchronized for the engine to run well. If you can find a flow meter gauge, commonly used on old British sports cars, this will make life easier. Mine is called a Unisyn and I've had it for 25 years. If you have the tool, you know how to use it, so enough said.
Start with a warm engine. There are three adjustments on each carburetor. These are the cable adjuster at the top, the idle speed stop on the bottom (at an angle) and the idle air bleed screw on the side.
Start by loosening the locknut on the bleed screws of both carbs and screwing them in gently all the way. Now back both out 1.5 turns and tighten the lock nuts just a bit.
Next, loosen the lock nuts on the idle speed screws. Turn these screws out until no resistance is felt.
Now run them back in until you can barely detect upward movement of the throttle slide. This is better accomplished with a clean finger touching the throttle slide than by eye.
Now tighten the lock nut on one side. On the other side, disconnect the spark plug wire and ground it by plugging an old spark plug in and laying it on top of the cylinder head.
Screw in the speed screw a couple of turns and start the engine. Run the screw in and out until you get the lowest idle you can get without the engine stalling. Tighten the lock nut.
Now back out the idle air bleed screw one half turn at a time. The idle speed should go up. At some point the mixture will become too lean and the engine speed will start to decrease again. Back the screw in to maximum RPM and then run it in again one more half turn. Set the lock nut and turn off the engine. Repeat the process on the other side.
Now hook up both spark plugs and start the engine. It should start and idle smoothly. If the idle speed is too low, adjust both idle speed screws in an equal amount. Blip the throttle. If the engine hesitates or coughs, adjust both air screws in one half additional turn. Do this until the hesitation disappears and the idle speed is steady and not too slow. If it gets too slow, adjust the stop screws again.
Lastly, adjust the cable adjusters until there is almost no free play on either side. Now, with the engine off and the slides all the way in the down position, look at one slide at the same time you have a finger lightly placed on the other side (because you can't see both at the same time). Turn the twist grip slightly and adjust the cables so that both throttle slides lift off at precisely the same time. This takes a few tries. Remember to keep your hands clean! Replace the rubber rain boots. If you push on them, they will cover the tops of the carburetors and keep moisture out.
Now go ride the bike and see how it runs on the road. If things are good, ride it for a few days and then remove the spark plugs. The color of the electrode should be brown or tan. If it is white, the mixture is too lean, and if it is black, the mixture is too rich. Adjust the mixture by lowering or raising the metering needle. Raising it a notch at a time richens the mixture, and lowering it leans out the mixture. To get to the metering needle, loosen the ring nut at the top of the carb and pull out the slide. There is a little clip that holds the needle in place. Slide off the clip, move the needle up or down, and replace the clip. Don't lose the %$#@#$ clip! Now do the same for the other carburetor. Drive the bike again for a few days and check the spark plugs again. If your bike is still not running beautifully, check the points and timing.
Note: I prefer a fast idle speed. Since this engine uses oil slingers, a faster engine idle speed will circulate more oil to the piston bottoms at idle and keep the engine cooler. In warm weather this is very important. It is also important to turn off the engine if it is going to idle for more than five minutes. This comes straight from BMW and I didn't make it up.
The 1973 Chilton BMW manual describes this process a little differently. It recommends at each step of the operation to pull a spark plug wire and listen to the engine, then pull the other one. Whichever side runs slower, adjust the idle speed screw so that both cylinders run independently at the same speed. Then do the same thing with the air bleed screws. The idle speed will then be too fast, so back off the idle speed screws equal amount for both cylinders. Chilton recommends a millimeter of free play on the throttle cables.
The exhaust system consists of a header pipe and a muffler for each side. The sides are not interchangeable.
Install the header pipes into the exhaust ports of the cylinder heads. Make sure you use some anti-seize compound on the finned nut threads. You can get this at an automotive supply store.
Tighten the finned nuts somewhat, but do not tighten completely. The mounting ears attach to the foot peg studs. Loosen the nut, slip on the mounting ear and reattach on each side. The right tool for this is a BMW fin wrench, which costs about $40. If you don't have access to one, you can use a strap or chain wrench (or even a pipe wrench if you are careful) to tighten the finned nut.
Next, slip the mufflers over the ends of the header pipes. The mufflers are hung from the inside on the lower shock absorber pinch bolt. On the right side this is a tight fit. On the left side it is quite easy. Tighten this bolt on each according to the torque listings. The castle nut on the front of the muffler can be tightened with the special tool in the tool kit that looks like a hook, a hammer and punch (ouch!) or a pipe wrench/channel lock. If using a pipe wrench or channel lock pliers, wrap duct tape or masking tape around the nut at least two layers thick. This will prevent the chrome from being ruined.
Lastly, tighten the ring nuts on the cylinder heads until the packing is comfortably tight and nothing is slipping. Over tightening risks stripping the threads in the cylinder head. *Don't forget that anti-seize compound!*
