SJRoome
Registered user
Hi all
For the last few weeks I have been aware that my carbs were a bit out of tune, and as it was a beautiful day on Saturday I spent a happy hour cleaning them. I took photographs all the way through so I could share my approach.
I don't have any access to compressed air, so I use aerosol cans of carb cleaner and air. You will also need a 6 inch length of car window washer pipe, a 10mm flat spanner, a screwdriver with a flat blade and clean rag.
First off remove one carb. My approach is to drain the float bowl; remove the air pipes, let the carb hang on the cables, remove the cables trying to keep the tightening nut stationary on the threaded end of the cable, remove the fuel pipe. This is the right hand 40mm Bing carb from my 1989 R100GS.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb1.jpg" border="0" alt="Photobucket"></a>
I then remove the float bowl and look for debris. I clean inside the float bowl and check that the brass vent pipe is not blocked.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb2.jpg" border="0" alt="Photobucket"></a>
It is very easy to get blockages in the tiny jet in the tube in the corner of the float bowl. I blow this through with carb cleaner using the 6 inch length of pipe.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb3.jpg" border="0" alt="Photobucket"></a>
Then remove the main jet assembly using the 10mm spanner.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb4.jpg" border="0" alt="Photobucket"></a>
I dont normally remove the main jet from the jet holder. Just check that the main jet is clear and that the o ring has no splits and isn't perished. Remove the needle jet and its holder from the carb body by gently pushing it out with a finger. Next have a good look into the emulsion chamber. If you need to clean it inside, lift the slide by hand to keep the needle out of the way and use carb cleaner on a rag. A wooden skewer can also be useful.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb5.jpg" border="0" alt="Photobucket"></a>
Next remove the pilot jet using the flat screwdriver, being careful not to damage the slot.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb6.jpg" border="0" alt="Photobucket"></a>
Check the o ring for splits and being perished then blow it through with carb cleaner. I do this by screwing it into the 6 inch pipe. However you will need to hold the jet very tightly when doing this as the force on it is quite high. If you dont hold it it will shoot out for at least 10 feet!
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb7.jpg" border="0" alt="Photobucket"></a>
I then dry all the holes in the jet using canned air and check that they are clear.
Next carefully screw in the mixture screw counting the number of quarter turns it takes to reach the end of its travel. Remember this, or better yet write it down, and then unscrew and remove the mixture screw.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb8.jpg" border="0" alt="Photobucket"></a>
Again check the o ring, and look at the tip of the screw for fouling. Using the 6 inch pipe, blow carb cleaner into the mixture screw hole.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb9.jpg" border="0" alt="Photobucket"></a>
The smallest airways are those the feed the two tiny holes that are in the venturi under the throttle plate when it is at rest. These effect the pick-up from idle. To clear these blow carb cleaner into the idle jet holder whilst holding the throttle open. You should see jets of cleaner streaming out from both holes.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb10.jpg" border="0" alt="Photobucket"></a>
Now the carb is all clean simply re-assemble. Start by replacing the main jet assembly. Drop the needle jet and its holder into the main jet tube, over the needle and wiggle until the needle jet holder drops though so that a little shows in the venturi. Then gently screw in the main jet holder by hand, finishing off gently with the spanner. They go in in this order.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb11.jpg" border="0" alt="Photobucket"></a>
Replace the mixture screw, not forgetting the spring, and adjust it to the number of quarter turns you found when taking it out. Replace the idle jet.
Note that I did not disturb the floats or the float valve. I only remove these if the carb is leaking fuel.
Replace the carb on the bike and then clean the other one. Once you have done both check the free play in the throttle and choke cables. You are then good to go (although a tune would be a good idea).
For the last few weeks I have been aware that my carbs were a bit out of tune, and as it was a beautiful day on Saturday I spent a happy hour cleaning them. I took photographs all the way through so I could share my approach.
I don't have any access to compressed air, so I use aerosol cans of carb cleaner and air. You will also need a 6 inch length of car window washer pipe, a 10mm flat spanner, a screwdriver with a flat blade and clean rag.
First off remove one carb. My approach is to drain the float bowl; remove the air pipes, let the carb hang on the cables, remove the cables trying to keep the tightening nut stationary on the threaded end of the cable, remove the fuel pipe. This is the right hand 40mm Bing carb from my 1989 R100GS.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb1.jpg" border="0" alt="Photobucket"></a>
I then remove the float bowl and look for debris. I clean inside the float bowl and check that the brass vent pipe is not blocked.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb2.jpg" border="0" alt="Photobucket"></a>
It is very easy to get blockages in the tiny jet in the tube in the corner of the float bowl. I blow this through with carb cleaner using the 6 inch length of pipe.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb3.jpg" border="0" alt="Photobucket"></a>
Then remove the main jet assembly using the 10mm spanner.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb4.jpg" border="0" alt="Photobucket"></a>
I dont normally remove the main jet from the jet holder. Just check that the main jet is clear and that the o ring has no splits and isn't perished. Remove the needle jet and its holder from the carb body by gently pushing it out with a finger. Next have a good look into the emulsion chamber. If you need to clean it inside, lift the slide by hand to keep the needle out of the way and use carb cleaner on a rag. A wooden skewer can also be useful.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb5.jpg" border="0" alt="Photobucket"></a>
Next remove the pilot jet using the flat screwdriver, being careful not to damage the slot.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb6.jpg" border="0" alt="Photobucket"></a>
Check the o ring for splits and being perished then blow it through with carb cleaner. I do this by screwing it into the 6 inch pipe. However you will need to hold the jet very tightly when doing this as the force on it is quite high. If you dont hold it it will shoot out for at least 10 feet!
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb7.jpg" border="0" alt="Photobucket"></a>
I then dry all the holes in the jet using canned air and check that they are clear.
Next carefully screw in the mixture screw counting the number of quarter turns it takes to reach the end of its travel. Remember this, or better yet write it down, and then unscrew and remove the mixture screw.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb8.jpg" border="0" alt="Photobucket"></a>
Again check the o ring, and look at the tip of the screw for fouling. Using the 6 inch pipe, blow carb cleaner into the mixture screw hole.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb9.jpg" border="0" alt="Photobucket"></a>
The smallest airways are those the feed the two tiny holes that are in the venturi under the throttle plate when it is at rest. These effect the pick-up from idle. To clear these blow carb cleaner into the idle jet holder whilst holding the throttle open. You should see jets of cleaner streaming out from both holes.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb10.jpg" border="0" alt="Photobucket"></a>
Now the carb is all clean simply re-assemble. Start by replacing the main jet assembly. Drop the needle jet and its holder into the main jet tube, over the needle and wiggle until the needle jet holder drops though so that a little shows in the venturi. Then gently screw in the main jet holder by hand, finishing off gently with the spanner. They go in in this order.
<a href="http://photobucket.com" target="_blank"><img src="http://i717.photobucket.com/albums/ww177/SJRoome/Bing%20Carbs/BingCarb11.jpg" border="0" alt="Photobucket"></a>
Replace the mixture screw, not forgetting the spring, and adjust it to the number of quarter turns you found when taking it out. Replace the idle jet.
Note that I did not disturb the floats or the float valve. I only remove these if the carb is leaking fuel.
Replace the carb on the bike and then clean the other one. Once you have done both check the free play in the throttle and choke cables. You are then good to go (although a tune would be a good idea).