I think I’ve answered my own question? The throttle cables can slip right out of the carb “threaded” bosses so simply loosening the lock nut on the chock and throttle cables allows me to remove carbs easy enough.

what a learning curve!

My understanding is that our Bing CV carbs are actually quite good at compensating for changes in elevation without modification. 

Both the carb needles and needle jets are wear items. The wear will make the midrange more rich as it progresses. If you don’t know the maintenance history, I would start with fresh parts and stock settings. 

I also understand that moving the needle one position produces a rather significant change in mixture, probably more than might be desired. Changing the NEEDLE JET size is the finer adjustment. According to Mr. Snowbum, moving one notch on the needle is equivalent to approx 3 steps in needle jet size. 

Attached (I hope) is a chart produced by Bing with standard jetting for our carbs. Go by carburetor numbers, not motorcycle models. If yours is a ‘78 R100/7 with 32mm carbs, than I AM GUESSING that your stock setup would be 2.68 needle jets, and needles at position 3. Again, if you don’t know the history, I’d start stock with fresh parts. Then, should you want to try a slight adjustment, you could move to say 2.66 needle jets.

These are just my thoughts and opinions.  I’m certainly no authority on these matters  

Maybe there is someone here that also lives at 7000 feet, and would have some input. 

Posted by: @mark-creek

I just bought my ‘78 R100/7 at an elevation of 1,000-2,000 feet. Its new home is at 7,000 feet. I rode for 30 minutes and pulled the clutch/cut motor and I had a black plug (pic attached). I was thinking of dropping the needle one spot to #2. 

Mark -

Welcome Aboard !!

Why don't we start with some basics....

• First of all, lets make sure you have the correct plugs before we go changing things. Maybe it's as simple as too cold of a spark plug. Wouldn't that be something. Most of the newer plug charts are wrong, and the plugs in your owners manual are no longer made, which means it's a very good question.
• Secondly, the plug color reflects the state of the compression, ignition timing, fuel type, and 10 other static tuning adjustments that are quantifiable. Wouldn't you feel foolish if several weeks from now you reset the ignition timing only to find out that you need to un-do all the carb work? That's why we always do a complete tune-up first, BEFORE we start messing with the carbs. In the "food chain" of a motorcycle engine, everything else gets adjusted of FIRST.
• One of those tune up things is plug wires. 1) Exactly how old are your plug wires and plug caps? And 2) are they metal core wires?
• Another one of those tune-up things is your air filter. A clogged air filter cuts off the air intake, which forces the engine to ingest more.... you guessed it... fuel. Which would make the plugs darker. So it would be nice to know the age of your air filter.

And BTW, to complete the tune-up you're going to need a carb balance tool of some sort, and an ignition strobe lamp. You're also going to want to fit the latest Bing floats and float needles too.

So all in all, it's a worthy adventure, but you're not nearly ready to start messing with any carb adjustments. 

Hope this helps.

@wobbly

thanks so much for the nice welcome. Yes, I’m aware. All considered and adjusted first,  As my repertoire of skills grows, simple cable knowledge has not and I wanted to get thoughts on how others are pulling needles on the bike without as much disruption.

On my ‘78 w/40mm Bings;

Choke - I just break loose the top locknut at the boss on the carburetor cap. Then, spin the bottom locknut completely off and let it fall down the cable. The entire cable can then be lifted up and disengaged from the boss on the carb cap (without undoing the cable from the little choke arm below).

Throttle - DON’T loosen the cable adjuster at the boss on the carburetor cap. Leave that alone to preserve your adjustment.  Reaching behind the carb and lifting the throttle arm creates a bunch of cable slack. You will see that there is a slot in the arm that will allow you to unhook the cable from the arm (with a little fussing, of course). Unhook the throttle cable and just let it be. 

You can now remove the two screws holding the cap on the carburetor. Lift the cap straight off, taking care to keep that throttle cable happy. You can lay the cap aside on the cylinder, again carefully with the cable still attached. You can then remove the spring and lift the carb piston with needle out of the carb body. To reassemble, you will need to remove the intake tube so you reach into the carb and guide the needle into the needle jet. 

I think this is the least disruptive way to get to the needles. 

Posted by: @mark-creek

@wobbly

thanks so much for the nice welcome. Yes, I’m aware. All considered and adjusted first,  As my repertoire of skills grows, simple cable knowledge has not and I wanted to get thoughts on how others are pulling needles on the bike without as much disruption.

Mark -

I took a long time, thought about your issue, and typed you up a very lengthy reply because I thought you were serious about repairing this bike. The information I requested is simple. It may seem silly to you, but I assure you each answer is necessary for a correct diagnosis.

Your answer completely ignores my offer of help. That's too bad.

All the best, my friend.

Hello Mark. I just had sinus surgery, so I’m laying low for a few days and have too much time on my hands!  Anyway, for your entertainment, I’ll share a little reassembly tidbit. Again, this experience is with my 40mm Bings.

I used to endure mild to moderate frustration when it came to re-installing the carb pistons and cap, namely with getting the diaphragm to lay nicely in the groove around the carb top.  Most of the time the diaphragm just won’t lay down, and it’s hard to feel sure that the cap will push it down into place. I saw this technique being used on some Mikuni carbs. I will attempt to attach pictures. 

First step is fold the diaphragm down around the piston. Then, drop the piston in, guiding the needle into the jet, BUT don’t let it all the way down.  Instead, insert a paint stick into the carb mouth, and set the piston on the paint stick. This will hold it at the exact right position, and the folded down diaphragm will lay securely in the groove. Be sure the orientation tab on the diaphragm is in the notch. Then drop on the spring and re-install the cap. Lastly, of course, remove the paint stick.  Ta-da! No frustration. 

Wow. The system posted my entry 3 times. It keeps kicking me out and I have to start over. Hmmm. Technology. Here is another picture. See the paint stick holding the piston in position. 

Install spring and cap, secure, then remove the paint stick. 

The plug does not look sooty enough to worry about, IMHO. How does the bike start, and run? How about gas mileage? If it ain't broke, don't fix it. If it starts, idles and performs OK, maybe give it 1000 miles or so before trying to 'fix' it. Again, I do not see an issue with the pic of the plug. Also, once again, JMHO. 

thank you all, richard, I appreciate your response and applied what you said. I think you misunderstood my response. You are awesome!