Bing Jetting advise

[drpetemurray]

I give up, the bike runs strong, no hesitation, and proper mixture. What is the problem other than rocking at idle?

What is it you are looking for? IF you are looking for a smooth idle, either you are setting idle speed too low or idle mixture on one or the other carb needs to be tweaked not in 1/4 or 1/2 turns but minute increments. The recommended mixture settings are starting points.

I mean come on, if the bike is running strong, no hesitation, good fuel economy, proper plug color, ride it as long as it doesn't stall at idle and is fairly smooth. St.

I appreciate your response albeit a bit truculent. I am trying to tune to a proper standard.

[schrader7032]

Engine rocking could be due to differential timing. Have you looked at that before?

Kurt

[srankin]

I am sorry I come across a bit truculent, If you consider the Bing recommended settings to be a measure of proper standing than good luck. They are starting point recommendations so the bike will run well enough to fine tune the carbs. 1/2 out is a starting point and you may have to either back off or turn in perhaps 1/64 of a turn from that starting point to get a smooth idle. That is proper tuning to obtain proper idle as LONG AS there are no other issues with valve adjustment or ignition. The same goes for the individual idle speed adjustments.

As you have found at certain times in the carburetor's operation there is a transfer from the idle circuit to the running circuit. You have established you get good performance and proper mixture at the 1/2 setting. Have you done fine adjustments to the idle mixture to determine if there is any change or have you only done 1/4 turns and 1/2 setting? Maybe the right carb needs to have the idle mixture screw set at 3/8 out and the left 1/2? Am I clear?

"Clip positions on the needle are crude jumps in fuel flow".

If I am reading correctly, you are thinking about making a major change. Moving the needles. This is a crude change and I can say from long experience if you have a powerful running bike with good fuel economy and have established proper mixture by assessing the spark plug color after a long ride, you will find moving the needles up a notch or down is going to do more harm than good. The same thing will happen if you change the main jets.

Personally I am a fan of setting idle speed as low as I can get, for me 1000RPM is high, but that is me. Talking to my airhead shop owner, he suggested maybe bumping your idle up a hair to smooth things out. Maybe your bike idles best at 1050RPM maybe 950RPM. Like the mixture settings any listed figure will be a starting point. Who knows, maybe your two carbs are not synchronized for equal idle speed? Have you tried minor adjustments on that?

So yeah, I can be a jerk but I am trying to help you the best I can without your bike at hand and limited to writing in the forum. I also don't know you or your level of mechanical skill. If you feel the need to change the needles or jets, no problem. Maybe I will be wrong, it would not be the first time. Good luck, St.

[malmac]

Lots of good help has been coming your way.. I would not contradict or really add to that detail.

I have a digital temperature gauge.
When I have one of the bikes reasonably sorted - sort of at the fine tuning level.
I use the gauge to assess how hard each cylinder is working.
The heat levels change fairly quickly when one cylinder is doing more work than the other.
This is not measuring carburation but rather the end result of all the inputs, including differential timing etc.

If one head is running hotter then it is working harder. (for some reason).
I find it provides a different take on the question, a bit like your Doctor running a different blood test.
If you exhaust the adjustment options available through adjusting your carb settings and still have unequal head temps, then you can review other aspects of your engines running conditions.

I hope you get you bike tuned to your total satisfaction.


Regards

Mal

[drpetemurray]

Engine rocking could be due to differential timing. Have you looked at that before?

Kurt

Indeed, As noted in the opening post.

[Copy Paste]
Disclaimer the carbs have been fully rebuilt and balanced with the Carbmate, float levels are properly set, valves properly adjusted, static and advanced timing verified with a timing light. no air leaks.

Thanks

[schrader7032]

Pete -

You mentioned you did static and advanced timing...but that's not what I was referring to. Differential timing is where one cylinder fires earlier or later than the other. Each cylinder fires every time one of them comes to the firing point (points open). This is wasted spark...just one of the cylinders fires, the other has no fuel charge and the spark just goes wasted. This situation is caused by a worn out advance unit as well as how the advance unit is secured to the front of the engine.

The easiest way to see if there is differential timing is to look at the marks seen in the timing window with a timing light. If you see the S-mark quite clearly, then both left and right firings are at the same time during the engine rotation. If you see fuzzy images, then you have differential timing. Mac pointed out a way to see if one cylinder is working harder than the other. Differential timing can cause a cylinder to run inefficiently and if far enough off you could get pinging. The actual difference between left and right firing can be observed manually. Vech has mentioned that if the difference in firing point is on the order of 3/16" that might be too much.

If you don't have differential timing, then forget all above!

[drpetemurray]

I am sorry I come across a bit truculent,
[If you consider the Bing recommended settings to be a measure of proper standing than good luck.]

I never stated that.

They are starting point recommendations so the bike will run well enough to fine tune the carbs. 1/2 out is a starting point and you may have to either back off or turn in perhaps 1/64 of a turn from that starting point to get a smooth idle. That is proper tuning to obtain proper idle as LONG AS there are no other issues with valve adjustment or ignition. The same goes for the individual idle speed adjustments.

As noted in post 1 after the disclaimer, yes valves adjusted etcetera

As you have found at certain times in the carburetor's operation there is a transfer from the idle circuit to the running circuit. You have established you get good performance and proper mixture at the 1/2 setting. Have you done fine adjustments to the idle mixture to determine if there is any change or have you only done 1/4 turns and 1/2 setting? Maybe the right carb needs to have the idle mixture screw set at 3/8 out and the left 1/2? Am I clear?

Synchronized the carbs initially and after subsequent adjustments. After the initial sync tuning adjustments were made equally to each carb idle mixture screw. Following the IMS adjustment idle speed was adjusted
"Clip positions on the needle are crude jumps in fuel flow".

0FF]Agree[/color].

[[[[If I am reading correctly, you are thinking about making a major change. Moving the needles. This is a crude change and I can say from long experience if you have a powerful running bike with good fuel economy and have established proper mixture by assessing the spark plug color after a long ride, you will find moving the needles up a notch or down is going to do more harm than good. The same thing will happen if you change the main jets.]]

>>No you misunderstood I would first change the jet needle. One change in the clip position is about a >>2,5 greater jump in the next incremental jet size.


Personally I am a fan of setting idle speed as low as I can get, for me 1000RPM is high, but that is me. Talking to my
airhead shop owner, he suggested maybe bumping your idle up a hair to smooth things out. Maybe your bike idles best
at 1050RPM maybe 950RPM. Like the mixture settings any listed figure will be a starting point. Who knows, maybe
your two carbs are not synchronized for equal idle speed? Have you tried minor adjustments on that?

>>I set the idle speed at the upper threshold of oil pressure indicator light flicker. Yes I have tried >>increasing idle slightly without benefit

So yeah, I can be a jerk but I am trying to help you the best I can without your bike at hand and limited to writing in
the forum. I also don't know you or your level of mechanical skill. If you feel the need to change the needles or jets,
no problem. Maybe I will be wrong, it would not be the first time. Good luck, St.

>>No apology necessary.
>>But since you asked here is a brief description of my motorcycle experience and mechanical skills. Riding and working >>on bikes for over 53 years. I have raced, tuned, jetted, and rebuilt MX bikes for many years. Restored antique HD >>motorcycles to Senior First AMCA standard. Ground-up restoration of this bike in question my 73 R75/5. The /5 was >>judged by the AMCA in September with a qualifying award of junior first 98 1/4 points out of 100. Competed in many >>extreme Long Distance motorcycle events with many accolades.

>St perhaps you can explain this. In all my experience historically a richer fuel setting yields a darker plug reading not a >leaner fuel setting. As noted I've established the bike performed notably better with a leaner idle mixture screw >setting.( I get it this implies the IMS setting was rich) Prior to the lean setting IMS turned in, the plug reading was lean. >With the IMS in the lean setting my spark plug reading is tan. Why?

>Again thanks for the help, I welcome others to comment regarding this spark plug reading phenomenon.
(somehow the bottom of the reply all of the font color change to blue my error

[drpetemurray]

Mal great information and thanks. I do use the digital temp gauge and will check again once sorted.

[drpetemurray]

Pete -

You mentioned you did static and advanced timing...but that's not what I was referring to. Differential timing is where one cylinder fires earlier or later than the other. Each cylinder fires every time one of them comes to the firing point (points open). This is wasted spark...just one of the cylinders fires, the other has no fuel charge and the spark just goes wasted. This situation is caused by a worn out advance unit as well as how the advance unit is secured to the front of the engine.

The easiest way to see if there is differential timing is to look at the marks seen in the timing window with a timing light. If you see the S-mark quite clearly, then both left and right firings are at the same time during the engine rotation. If you see fuzzy images, then you have differential timing. Mac pointed out a way to see if one cylinder is working harder than the other. Differential timing can cause a cylinder to run inefficiently and if far enough off you could get pinging. The actual difference between left and right firing can be observed manually. Vech has mentioned that if the difference in firing point is on the order of 3/16" that might be too much.

If you don't have differential timing, then forget all above!

I will look into this. With the timing light, my S and F marks were solid. I replaced the springs in the spark advance unit upon rebuild and the unit does not appear worn.
Thanks

[srankin]

>St perhaps you can explain this. In all my experience historically a richer fuel setting yields a darker plug reading not a >leaner fuel setting. As noted I've established the bike performed notably better with a leaner idle mixture screw >setting.( I get it this implies the IMS setting was rich) Prior to the lean setting IMS turned in, the plug reading was lean. >With the IMS in the lean setting my spark plug reading is tan. Why?
Pete, I am impressed with your experience. As to the above question, I can only answer, I agree with the richer fuel setting yielding a darker plug and the converse. IF you started out with dark plugs and poor performance at initial Bing recommendations, for needle settings, main jet settings, and idle screw mixture adjustment, and found by slightly leaning out the idle mixture, performance improved and plug color lightened. That is part of fine tuning and can be expected. You start with the recommendations and go from there.

I am trying very hard to understand here. At this point, the bike runs fine with rock at idle?

Do I not make myself clear that perhaps minor tweaking of idle mixture not of both carbs at the same time but one carb at a time may smooth things out? Have you tried that?

Setting the each carb exactly the same doesn't always work. Allowances have to be made for individual carb variances. So as I wrote, setting one carb to 1/2 may be spot on, the other carb may need to be 33/64 to get the same final performance, and running mixture.

The idle system only works at a tiny fraction of throttle opening, at that point needle position takes over. And at that point, you are saying you have a good running bike with proper plug color or assumed fuel mixing. However in that fraction of a point in time between true idle and run, one carb may be a bit richer or leaner at total idle but that difference won't be noticed during riding or acceleration. It may however be noticeable at idle. St.