Hi. Can some one please explain to me (or direct me to the right net site) how can I adjust my carbs? I took them off for repairing and now they are on the motor again. I only know that each carburetor should be adjusted individually. Thanks in advance.
Micha.
R51/3 Carb adjusting;
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Allan Atherton
Re: R51/3 Carb adjusting;
This assumes your ignition system, timing, valves and carbs are all working properly. If the spark is weak, the timing is off, valves are tight, and the carbs are dirty or worn out, then carb adjusting may not make the bike run as it should.
Pull up the rubber cable boots at the carbs, so they are up on the cable sheath. Put some grease on everything so the boots will slip back down easily later when you are done adjusting.
The throttle cables should be installed in the throttle housing so there is no slack in the chain. Then make sure the throttle cables have a little slack or play in them, so they are not always pulling on the slides and affecting the idle. You should be able to turn the throttle a little bit before you feel the resistance of the slides. At the carb end, this play is created by your being able to pull the cable up a little bit before feeling the slide. The current BMW Mobile Tradition high bar cables seem to have too little cable exposed outside the sheath to get any slack even when the carb adjuster is screwed all the way in. If this is so, I have found NOS Flanders cables have more exposed cable, but are not as smooth.
Loosen the lock nuts on each idle mix screw and turn each screw in to find its bottom, then back out two turns and lock gently. This takes a 9mm box end with a thin box (ground down) with a medium screwdriver inserted through the box.
Start cold bike by turning gas on, kicking slowly 2 times, then tickling each carb to a count of two, pressing in the key, opening throttle a wee bit (a hair), and giving one hard kick followed immediately by another hard kick (two seamless kicks without pause). If it started, then reach down and press each tickler for one count. (Hot bike and flooded bike have other, different drills.)
Let bike idle for two minutes to warm up a little. If weather is hot, and if your adjusting takes a long time, it is good to put a large box fan in front of the bike and turn it on after motor gets really hot.
Put a leather work glove on one hand to protect against heat and shocks, and remove and replace one plug wire then the other, while listening to which side is idling faster. Turn in the idle stop knurled screw on the slow side, to raise the slower slide so both sides run at about the same RPM.
(Electrode extenders are a better way of turning off the spark plugs as they protect the coil by not making the killed spark jump the safety gap above the coil. This can be bad for the coil. The extenders are bolts with the same thread as the end of the spark plugs, with their heads cut off and replaced with spark plug tips -- the little things we throw away. The tips become unions, allowing the threaded rods to be added to the tops of the plugs, exposing a bare section of electrode that can be shorted out with a big screwdriver. To plunk along on one carb for getting its best adjustment, just wedge a screwdriver under the opposite electrode. To synch the carbs, slide screwdrivers back and forth to seamlessly ground one side then the other, transferring the spark instantly from one side to the other. This will immediately show any difference in rpm. In the paragraphs below, instead of pulling off and putting back the spark plug cap, just slide the screwdriver along the fins to touch the electrode. See photos at the site http://www.flickr.com/photos/roundel/sets/437125/.)
With bike idling, unlock and turn each idle mix screw in and out to find where it makes its cylinder idle fastest, then turn it in 1/4 turn more and gently lock it.
Now that each cylinder has basic idle mix set, pull off one spark plug cap and the other to see if each side runs at same RPM alone. Use the idle stop screws again to either speed up or slow down one side or the other.
The idle when hot should be fast enough so you don’t worry about stalling at a stoplight. This idle may seem too low when first started cold.
After the idle is adjusted, synchronize the throttle cables next.
Open the throttle a little and listen to see if one side starts pulling harder, ie if one slide is coming up before the other. If this is happening, there will be a little roughness, shaking or rocking in the transition from idle to throttle. Loosen the cable adjuster locknut on your side (9 mm open end), open the throttle again a little, and turn the cable adjuster back and forth until the carbs sound synchronized. (Or use the electrode extenders to instantly transfer spark from one side to the other to see which is faster.)
Lock the cable adjuster nut and slip the cable boots down onto the carbs.
Pull up the rubber cable boots at the carbs, so they are up on the cable sheath. Put some grease on everything so the boots will slip back down easily later when you are done adjusting.
The throttle cables should be installed in the throttle housing so there is no slack in the chain. Then make sure the throttle cables have a little slack or play in them, so they are not always pulling on the slides and affecting the idle. You should be able to turn the throttle a little bit before you feel the resistance of the slides. At the carb end, this play is created by your being able to pull the cable up a little bit before feeling the slide. The current BMW Mobile Tradition high bar cables seem to have too little cable exposed outside the sheath to get any slack even when the carb adjuster is screwed all the way in. If this is so, I have found NOS Flanders cables have more exposed cable, but are not as smooth.
Loosen the lock nuts on each idle mix screw and turn each screw in to find its bottom, then back out two turns and lock gently. This takes a 9mm box end with a thin box (ground down) with a medium screwdriver inserted through the box.
Start cold bike by turning gas on, kicking slowly 2 times, then tickling each carb to a count of two, pressing in the key, opening throttle a wee bit (a hair), and giving one hard kick followed immediately by another hard kick (two seamless kicks without pause). If it started, then reach down and press each tickler for one count. (Hot bike and flooded bike have other, different drills.)
Let bike idle for two minutes to warm up a little. If weather is hot, and if your adjusting takes a long time, it is good to put a large box fan in front of the bike and turn it on after motor gets really hot.
Put a leather work glove on one hand to protect against heat and shocks, and remove and replace one plug wire then the other, while listening to which side is idling faster. Turn in the idle stop knurled screw on the slow side, to raise the slower slide so both sides run at about the same RPM.
(Electrode extenders are a better way of turning off the spark plugs as they protect the coil by not making the killed spark jump the safety gap above the coil. This can be bad for the coil. The extenders are bolts with the same thread as the end of the spark plugs, with their heads cut off and replaced with spark plug tips -- the little things we throw away. The tips become unions, allowing the threaded rods to be added to the tops of the plugs, exposing a bare section of electrode that can be shorted out with a big screwdriver. To plunk along on one carb for getting its best adjustment, just wedge a screwdriver under the opposite electrode. To synch the carbs, slide screwdrivers back and forth to seamlessly ground one side then the other, transferring the spark instantly from one side to the other. This will immediately show any difference in rpm. In the paragraphs below, instead of pulling off and putting back the spark plug cap, just slide the screwdriver along the fins to touch the electrode. See photos at the site http://www.flickr.com/photos/roundel/sets/437125/.)
With bike idling, unlock and turn each idle mix screw in and out to find where it makes its cylinder idle fastest, then turn it in 1/4 turn more and gently lock it.
Now that each cylinder has basic idle mix set, pull off one spark plug cap and the other to see if each side runs at same RPM alone. Use the idle stop screws again to either speed up or slow down one side or the other.
The idle when hot should be fast enough so you don’t worry about stalling at a stoplight. This idle may seem too low when first started cold.
After the idle is adjusted, synchronize the throttle cables next.
Open the throttle a little and listen to see if one side starts pulling harder, ie if one slide is coming up before the other. If this is happening, there will be a little roughness, shaking or rocking in the transition from idle to throttle. Loosen the cable adjuster locknut on your side (9 mm open end), open the throttle again a little, and turn the cable adjuster back and forth until the carbs sound synchronized. (Or use the electrode extenders to instantly transfer spark from one side to the other to see which is faster.)
Lock the cable adjuster nut and slip the cable boots down onto the carbs.
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Michael Steinmann
Re: R51/3 Carb adjusting;
Wow... Thanks a lot!
Will try it first thing tomorow.
Will try it first thing tomorow.
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peter berry
Re: R51/3 Carb adjusting;
You may notice a little difference on the R51/3 than Allan describes from my experience the R51/3 throttle doesnt snap bak under spring pressure so you need to be careful with the first step around cable slack and you need to makke sure that the throttle is allowinng the slides to return to the bottom . My R51/3 throttle is no where as smooth as my R50. That said I have used Allans proceedure with great success . Ed Korn sells the plug extenders for $5. and they make the job easy . I also have a little flow meter that I purchased that really helps to simplify this proceedure Cheap and available thru one of the US catalogue dist If you are interested let me know and I will get name Peter
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Allan Atherton
Re: R51/3 Carb adjusting;
Maybe this is the Sheleyer Carbureter Synchronizer, available from J.C Whitney Co. in their web catalog:
http://www.jcwhitney.com
Enter search word synchronizer or the number ZX882792N
I have one but never use it. You have to remove the bike's air tubes. The device obstructs the carb it is used on, while the opposite carb runs free. This introduces an imbalance in the carb adjusting, increasingly so at RPMs higher than idle.
http://www.jcwhitney.com
Enter search word synchronizer or the number ZX882792N
I have one but never use it. You have to remove the bike's air tubes. The device obstructs the carb it is used on, while the opposite carb runs free. This introduces an imbalance in the carb adjusting, increasingly so at RPMs higher than idle.
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Han Verhagen
Re: R51/3 Carb adjusting;
Allan,
On my R50 I adjust the idle setting and the synchronization of the carbs with 2 air flow meters mounted on the carb air intakes. The meters are :
BS400 from Midlock. Have a look at : http://www.midlock.nl/Adobe_engels/Inde ... nizers.pdf
The resistance to the inflowing air is minimal. While idling you do not notice a change in rev when removing the meters.
This way of carb tuning is very precise. It is astonishing to see how a little displacement of a throttle cable is necessary to make the air flow meter move.
I am very happy with these meters.
Best regards
Han Verhagen
On my R50 I adjust the idle setting and the synchronization of the carbs with 2 air flow meters mounted on the carb air intakes. The meters are :
BS400 from Midlock. Have a look at : http://www.midlock.nl/Adobe_engels/Inde ... nizers.pdf
The resistance to the inflowing air is minimal. While idling you do not notice a change in rev when removing the meters.
This way of carb tuning is very precise. It is astonishing to see how a little displacement of a throttle cable is necessary to make the air flow meter move.
I am very happy with these meters.
Best regards
Han Verhagen
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Allan Atherton
Re: R51/3 Carb adjusting;
The Midlock synchronizer looks like the JC Whitney synchronizer that I have.