By Ron Schmidt
Throttle Cable Basics – BMW R259 Engine [R850, R1100, R1150]
The two most common reasons we see oil heads arrive in our shop on a truck or trailer are broken throttle cables and broken alternator drive (poly v) belts.
This seminar is to show you how to do a road side replacement of throttle cables. This seminar paper only addresses throttle cable issues and does not cover clutch cables. Now, before we get into the repair procedure on throttle cables, I would like to tell you how to NOT have to do this along side the road.
The cables and the alternator drive belt are wear items. They need to be inspected and are expected to be replaced periodically just like tires or brake pads. The easiest way to avoid problems is preventative maintenance!
We will discuss the two main types of throttle cables so you know which style you have, but for now I’ll just tell you that if you have the older 2 cable style the suggested replacement interval by BMW is 24,000 miles. The newer 4 cable with distributor replacement is suggested at 36,000 miles.
Oddly, we see almost no failure with the older 2 cable system, even with bikes having many more than 24,000 miles on them, yet have seen many of the new and “improved” 4 cable systems break the upper throttle cable even before the 36,000 mile replacement! So, as with all things in periodic maintenance, a careful inspection of problematic areas on a regular basis is better than just waiting until a specific mileage has been reached. In the case of the newer 4 cable system, I would suggest inspection of the upper cable every 6000 miles or so, just to be safe. In BMW’s defense, they have improved the cables for the 4 cable system and the frequency of failures has decreased since the improvements were made.
Also, this seminar is written as if you were not in a workshop with all the cool toys (like an accurate means of synchronizing the throttle bodies) and it assumes that you have a set of cables with you. It seems to me that if you are going to buy a new set of cables to carry with you, it would be better to have those cables installed before you are on a trip and then carry the old ones as spares for some poor rider who was not as forward thinking as you are and is stranded with a broken cable! We will show you how to get the cables installed and get the throttle bodies synchronized close enough to get to a proper repair facility to have the synchronization done properly.
Terms & Tools
Terms:
Throttle body: This is the air control valve that the cables attach to. There are two, one on each side of the motorcycle. It is the item that is just to the rear of the cylinder head that looks like a tube with some other items on it, about 4” long and 2” in diameter. The one on the left side has a black box on the outside of it that is about 2 ¼” square. The throttle body is normally silver in color, but on some models it will be black.
Synchronization: We will discuss the need to synchronize the throttle bodies. This simply means that the two throttle bodies, one on each side of the bike, need to be opening the same amount. This is necessary to keep the engine running smoothly.
Throttle Position Sensor (TPS): This is the 2 ¼” black square box that is on the left throttle body. It “tells” the Motronic unit (engine control computer) how far you have opened the throttle.
2 cable system: This is the earlier throttle cable system that uses one cable for the fast idle (marked choke but it is not really a choke) and one other cable that controls both throttle bodies. The easiest way to tell if you bike has this old system is to look at the left side throttle body. If it has 3 black cable housings with threaded adjusters on it, you have the old system. If there is only 1 cable going to the left throttle body, you have the new 4 cable system.
4 cable system: This system has 4 separate cables that meet in a distributor box that is under the battery. See two cable system notes above to determine if you have this system.
Vantage point: Left, right, front, and rear are all as viewed sitting on the motorcycle.
Tools and supplies:
All of the hand tools you need will be in your tool kit. They vary from model to model. You will also want to have available:
• This “seminal instruction” paper.
• A fuel line clamp or a pair of vise grip pliers.
• Throttle cables!
• Ten 7” zip ties—you will need more on some models than others, but never more than 10.
• A pair of rubber gloves if you do not want your hands to smell like gasoline when you are done.
• A shade tree if available.
• Some rags or paper towels.
• A lubricating spray like WD40 or chain lube.
Procedure
1) Park the bike on the center stand on stable ground (if possible, as side of the road repairs may prevent this luxury). You will be pulling and tugging a bit, so make sure it is as stable as possible. If it is hot outside, try to find a shady area because you will be working on it for a while!
2) Remove the fuel tank. On many models this will require removal of some fairing panels. It would be a good idea to know how to do this on your particular motorcycle when you are at home. (We are not going to go over this procedure for every model during this seminar due to time constraints).
NOTE: On older models that do not have the quick disconnect fuel fittings, you will have to pinch the fuel return line (the upper of the two larger rubber fuel lines that are on the right hand side of the bike that clamp onto the shiny plastic hard lines that go into the unknown depths of the engine area) to keep from draining the fuel tank.
This can be done with the proper fuel line clamp shown at the seminar, or with a vise grip pliers. If you use vise grip pliers, just make it tight enough to stop the flow by pinching the hose shut, being careful not to make it so tight that you cut the hose! The lower hose will not need to be pinched off as it will only dribble a few drops of fuel. Make sure you pinch only the rubber line, as far forward as possible so you do not damage the hard plastic line that the rubber hose clamps onto. If your bike has the quick disconnect fittings, you do not need to pinch the fuel lines at all as they stop the fuel flow automatically when they are disconnected.
HINT: If you regularly work on your own bike, or if you want to make real good friends with the people who do work on it, the quick disconnect fittings can (should) be installed if your bike does not already have them.
3) Once the tank is off, spend a few moments looking at how the cables are routed from the throttle twist grip and from the fast idle lever around the frame and other hoses, etc. This varies from model to model and needs to be duplicated exactly. Make a drawing if you think you might forget! Note if you have the 2 or 4 cable system as some of the instructions will differ.
4) Remove the upper throttle cable and upper fast idle cable fittings from the handle bar grip areas.
On the 2 cable models there is one Phillips head screw that can best be seen by standing in front of the motorcycle looking toward the rear of the motorcycle. It is black and holds a small cover that pulls off toward the front of the motorcycle after the screw is taken out. Once the cover is removed you will be able to see the barrel end of the cable where it fits into the twist grip. Pivot the cable upwards to align it with the slot in the twist grip and pull the barrel end to the outside to remove it. On the 2 cable models there is no reason to remove the fast idle cable from the upper end at the handlebar.
On the older 4 cable models (1997 onwards for R1100 models, until the R1150 was released — except the R1100S which always had the new style) the upper end of the throttle cable can be removed from the twist grip in the same manner as the 2 cable instruction above.
On the newer 4 cable model’s upper throttle cable (R1150’s and R1100S), there will be a small black Phillips screw that can best be seen by standing on the right side of the bike looking toward the left side of the bike. The screw is just under the rubber twist grip. The cover the screw holds on, can then be pulled off—it has a snap fitting and can be recalcitrant, but it will pop off with just a little force. Loosen the 10mm hex nut on the adjuster at the upper end of the cable and screw the adjuster all the way out of the plastic housing it is screwed into.
Once the cover is removed you will be able to see the barrel end of the cable where it fits into the twist grip. Pivot the cable upwards to align it with the slot in the twist grip and pull the barrel end to the outside to remove it.
On the newer 4 cable model fast idle cable there are a couple of different operating lever styles. If yours has an operating lever that is horizontal with a black plastic cover about 25mm in diameter that says choke on it, feel lucky and proceed as follows. Pry the black plastic cover up. Under it will be a large screw. Remove the screw. Note that there is a special washer under the screw head that has tabs on it. Pay attention to how this washer is in the lever so you can assemble it the same way, with the tabs down. Remove this washer. Now lift the lever up. The cable will come out of it usually as you lift it up. If your bike is has a fast idle operating lever that moves vertically, bummer.
Proceed as follows: Looking at the left handgrip from the left side of the bike, and by moving the big rubber flange of the grip out of the way so you can see the outside end of the plastic handlebar switch assembly, you will see 3 Phillips head screws; all black. There will be screws at 7 o’clock, 8 o’clock and 10 o’clock. The one at 8 o’clock is smaller than the other two. Remove this screw only and the lever will come right off, leaving the cable inside the switch housing. The cable can then be pulled out toward the front of the motorcycle.
If your bike has heated handgrips, double bummer. You may have to pull the grip towards the left side of the handlebar by removing the two Phillips screws that hold it onto the handlebar. These screws will not be visible until you pull the rubber of the grip back a little away from the switch. DO NOT PULL THE GRIP ANY FURTHER OUT THAN NECESSARY. PULL IT VERY CAREFULLY OR YOU WILL BREAK THE VERY SMALL WIRES THAT MAKE THE GRIP WORK!!
5) Follow the cable(s) and cut off any zip ties that are holding them to the frame.
6) Remove the throttle bodies.
Loosen the 10mm locknuts on each of the throttle cable adjusters at the throttle bodies (one on each throttle body for the new 4 cable system, OR one on the right side and 3 on the left side for the 2 cable system).
Loosen 2 clamps (as far as they can be loosened), one on each end of the air tube that goes from the rear of the throttle body to the air box. These tubes can then be pushed off the rear of the throttle body and into the air box. They often will be stuck to the rubber boot at the air box end. If they won’t move, slip a flat blade screw driver blade between the rubber boot and the plastic air tube and squirt some WD40 or similar between the two parts.
Locate the fuel injector.
The injector comes out of the throttle body at the top at about a 45 degree angle. It has an electrical connector on the top and a hard shiny plastic tube that goes on the back of it.
Pull off the square metal clip at the junction of the fuel injector and the high pressure shiny black plastic fuel line. Pull the line off the injector. A few drops of fuel will drip out of the line. Remove the electrical connector by pushing the metal bale wire at the front of the injector toward the injector and then pulling the connector up and off the injector. Do this on both throttle bodies.
On the left throttle body only, also remove the wire connector from the TPS by pushing the metal bale wire inward and then pulling the electrical connector down. There will also be an Allen bolt holding a wire to the bottom of the throttle body. Remove the Allen bolt and the wire.
Loosen the clamps at the front of each throttle body as far as the clamps will go. Pull the throttle body to the rear and out of the rubber boot. It will be easy now to remove the cables from the throttle bodies by unscrewing the cable adjusters out of their holders. (Note: “easy” is a relative term.)
7) Remove the cables.
On the 2 cable system, note the way the cable runs through the engine/transmission/airbox area. It will have to be routed the same way when the new cable is installed. The throttle cable can now be pulled out from the left side of the bike and “unwound” from the left side throttle body. Note how it wraps around the pulley on the left throttle body so you can duplicate it with the new cable.
On the 4 cable system, all the cables join at a distributor box that is held in place under the battery in a tray and secured with a clip that can be seen from the right side of the bike. This clip is hidden by a bent rubber hose about 20mm in diameter. Look past the hose and you will see the clip, just under the throttle cables. Push the clip down and slide the distributor block, with all 4 cables still connected to it, out toward the right of the bike. This will be easier if you spray some lube on the rubber hose and swear in German. Note the routing of the cables, particularly where the two from the left side of the bike go into the distributor block. The new cables will have to be routed EXACTLY the same way.
8 ) Install the new cables.
On the 2 cable system, just reverse the instructions used to remove the old cables on instructions 3 through 7, making sure that the cables are routed exactly the same and zip ties are replaced in the same locations they were removed from.
On the 4 cable system, install the new cable(s) into the distributor box exactly the way the originals were removed. The disc inside the distributor that the cables goes into is marked left and right on the disc. Pay attention! You will not know that you have installed the cables in the distributor incorrectly until you have reinstalled the distributor and re-routed all the cables, and then cannot synchronizes the throttle bodies — which will result in more swearing in German.
Slide the now assembled distributor/cable assembly back into its holder from the right side of the bike to the left side, once again being careful the cables that are coming out to the left side of the bike are routed through the same passages they were removed from.
If you are attempting to do this along the side of the road, by now you certainly are wishing you would have had this done before you left on your trip!!
9) Adjust the cables and synchronizing the throttle bodies.
On the 2 cable system, with the throttle twist grip completely closed (as if the bike were at idle) turn the fast idle cable adjuster counter clockwise (as viewed from the top) until you can pull the cable up just 1 mm without moving the lever arm that the cable operates.
Now, set the left side throttle cable adjusters as follows: With the throttle twist grip completely closed (as if the bike were at idle) turn the front cable adjuster counter clockwise (as viewed from the top) until the black cable housing can be pulled up only1 mm without moving the spool on the throttle body.
Now, adjust the rear cable adjuster up ½ of its adjustment — with as much of the cable adjustment threads above the plate it screws into, as it has threads below the plate. Tighten the lock nuts on these three cable adjusters.
Move to the right side throttle body and set the cable adjuster by turning it counter clock wise (as viewed from the top) until the cable can be lifted only 1mm without moving the spool. Fully open and close the throttle twist grip a few times.
Now open the throttle twist grip about ½ way and then close it slowly. You will be able to hear when the throttle spools come to rest against their stops. They should stop at the same time, i.e., you should only hear one click as they both touch, not two clicks as one closes before the other. If you hear two clicks, adjust the right cable adjuster until you only hear one click as you close the throttle. Make sure you can hear the click as the throttles close, even with the handlebars turned fully to the right and to the left. If turning the bars does not let the throttles close all the way, the engine will race when started if the bars are turned. That would be dangerous!
If turning the bars keeps the throttles from closing, re-do the adjustments, giving each adjuster ¼ turn clockwise (as viewed from the top) until you can once again hear one click as the throttles are closed with the handlebars turned fully in either direction.
On the 4 cable system, all 4 cables will need to be adjusted. The upper throttle cable is adjusted at the twist grip with the grip closed as if at idle. Turn the adjuster out until the black cable housing can only be moved 1 mm before resistance is felt. Tighten the lock nut. Repeat this adjustment for the fast idle cable at its adjuster.
Now adjust the two lower cables, one on each throttle body, so that the black cable housing can be moved only 1mm without turning the cable spool.
Listen for the single click as described above for the 2 cable system and adjust them the same way. Turn the bars fully side to side and make sure the click at the stop is still heard. Correct if needed by using the similar procedure described above for the 2 cable system.
10) Reinstall the fuel tank, fuel lines, fuel pump wiring connector, and vent hoses removed in step 2.
Remember to remove the clamp on the fuel return line before turning the key on. Turn the key on and off a few times and check the hose connections for leakage before starting the engine. Once you have determined that there are no leaks, start the engine. It should run smoothly. If it does not, recheck the synchronization and correct as needed.
11) Reinstall any fairing panels removed, pick up your tools, wash your hands (if water and soap are available) or wipe them on the grass or your now dirty pants, and go riding!
12) As soon as possible, take the bike to Bavarian Motorcycle Workshop so we can correctly set the throttle body synchronization with our electronic equipment!
