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Discussion Starter #1
Have been seeing several posts regarding pilot screw adjustments again and came up with an easy adjustment option.
Greg Phillips extension to the screw works very well, however my fingers aren't as nimble as they had been. I experimented with a piece of speedometer cable and came up a easily adjustable pilot screw that can even be adjusted when hot or riding down the road. For most of us, once adjusted it should be OK for the duration. For those fortunate enough to be changing elevations rapidly, this may be of help. If interested, perhaps Greg would be willing to make them up for you.
Have just tried mine on a 90 mile ride and it works like a charm.
The picture shows my version with a 10" length which enables minute screw adjustments while riding on a road with no traffic.
I will no doubt shorten it so it just sticks out far enough so as not to burn fingers when the engine is hot.
The two ends of the speedometer cable have been ground down and somewhat squared, then epoxied at each end. It takes very little effort to "bottom" the screw and then turn it out the recommended number of turns. In my case, 1 3/4 turns gave me good results both in starting and running down the road at 55 mph.
Hope this helps,

Senior citizen Ron
 

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Silver solder or brazing are more secure options for what is overall a very good idea.
I would tend not to trust a brittle adhesive like most epoxies that may degenerate over time with heat and vibration..
If and when the epoxy should fail I have found that a pair of very small diameter holes may be drilled into exposed end of mixture screw such that fine pointed tweezers can gain sufficient purchase to turn out and remove the otherwise unserviceable mixture screw.
 

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Have been seeing several posts regarding pilot screw adjustments again and came up with an easy adjustment option.
Greg Phillips extension to the screw works very well, however my fingers aren't as nimble as they had been. I experimented with a piece of speedometer cable and came up a easily adjustable pilot screw that can even be adjusted when hot or riding down the road. For most of us, once adjusted it should be OK for the duration. For those fortunate enough to be changing elevations rapidly, this may be of help. If interested, perhaps Greg would be willing to make them up for you.
Have just tried mine on a 90 mile ride and it works like a charm.
The picture shows my version with a 10" length which enables minute screw adjustments while riding on a road with no traffic.
I will no doubt shorten it so it just sticks out far enough so as not to burn fingers when the engine is hot.
The two ends of the speedometer cable have been ground down and somewhat squared, then epoxied at each end. It takes very little effort to "bottom" the screw and then turn it out the recommended number of turns. In my case, 1 3/4 turns gave me good results both in starting and running down the road at 55 mph.
Hope this helps,

Senior citizen Ron
i'm all for a better way to adjust for the perfect idle without getting burnt. i like the idea you are sharing with us. all though, i think some of your tuning proccesses are confusing. the "pilot" adjusting screw or what i have all was known it as the idle fuel air mixture adjuster, is for finding the perfect setting for a nice idle. if you are finding that adjusting that setting while moving down the road, gives you a better running mixture, then that tells me you have other problems with your carb, pilot or main, depending on what speed you are going. if you adjust the idle mixture screw to compensate at an off idle speed, then you won't have the perfect idle setting anymore. each circuit in the carb has it's own rpm range to control
 

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Discussion Starter #8
Correct me if I'm wrong but...did you simply GLUE to cable to the screw head?
No, I took a 6” piece of 2x4 and drilled a 1/8” hole in approximately the middle so the shaft of the screw would fit snug in the hole. I then used a larger drill to a depth of about 1/4” so the pilot screw would screw into the wood but not protrude through the bottom. Didn’t want to damage the needle portion. After clamping the 2x4 with the pilot screw in place to my drill press, I used 1/16” bit to drill to a depth of approximately 1/4”. The next step was to use an 1/8” bit to the same depth.
Then, I ground the end of the speedometer cable slightly square to fit into the hole. Mixed the epoxy and dipped the end of the cable an inserted into the hole.
Almost forgot, unscrew the pilot screw from the 2x4 before the last step. The other end was an old radio knob and just used the epoxy. Clean the speedo cable and screw with lacquer thinner before gluing.
 

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The mixture screw provides some fuel during all engine operating speeds, not just the idle circuit. So as grewen points out if a beneficial improvement at speed via a mixture screw adjustment is noticed then likely this indicates other problems with the carb.
This animation can sometime help understand the interplay of the various jets and metering orifices on the new style CV carbs:
 

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  1. After removing the plug, and adjusting the screw out 2.5 turns, it sure made a difference in low speed response. My needle was only about 7/8 of a turn out to begin with. It took a bit of playing with it to come to this adjustment. I'm at about 3500 feet altitude. Neat idea on using the cable!
 

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The 1/8th inch diameter x 1/4 inch hole has but approximately 0.003 square inches of surface area where epoxy joins the mixture screw and but about 1/4th of that contact area between cable and mixture screw. Assuming a high strength industrial flexible epoxy with an idealized 11,000 psi tensile strength ( 5,000 to7,000 psi is a more reasonable attainable tensile strength for consumer grade epoxies) one cannot expect the epoxy bond to resist a great shearing force. Silver solders in shear can expect to deliver between 17,000 to 36,000 psi strengths.
 

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No, I took a 6” piece of 2x4 and drilled a 1/8” hole in approximately the middle so the shaft of the screw would fit snug in the hole. I then used a larger drill to a depth of about 1/4” so the pilot screw would screw into the wood but not protrude through the bottom. Didn’t want to damage the needle portion. After clamping the 2x4 with the pilot screw in place to my drill press, I used 1/16” bit to drill to a depth of approximately 1/4”. The next step was to use an 1/8” bit to the same depth.
Then, I ground the end of the speedometer cable slightly square to fit into the hole. Mixed the epoxy and dipped the end of the cable an inserted into the hole.
Almost forgot, unscrew the pilot screw from the 2x4 before the last step. The other end was an old radio knob and just used the epoxy. Clean the speedo cable and screw with lacquer thinner before gluing.
Thank you...but in the end, it is just GLUE holding the two together, correct?
 

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Discussion Starter #13
The 1/8th inch diameter x 1/4 inch hole has but approximately 0.003 square inches of surface area where epoxy joins the mixture screw and but about 1/4th of that contact area between cable and mixture screw. Assuming a high strength industrial flexible epoxy with an idealized 11,000 psi tensile strength ( 5,000 to7,000 psi is a more reasonable attainable tensile strength for consumer grade epoxies) one cannot expect the epoxy bond to resist a great shearing force. Silver solders in shear can expect to deliver between 17,000 to 36,000 psi strengths.
Actually, I used JB Weld and there is no resistance to turning the screw in or out.
silver solder if you feel more comfortable with that.
Ron
 

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No offense Ron, was not condemning you idea.
Just that some of us have been down that road with JBWeld epoxy in years past for that specific application.
That is why I also included a proven method for removal of the mixture screw should a screwdriver no longer work on the modified mixture screw if the glue bond fails.
My comments were not theoretical, but rather based on personal experience.
Hope you have butter success over time than I did.
 

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Discussion Starter #17
No offense Ron, was not condemning you idea.
Just that some of us have been down that road with JBWeld epoxy in years past for that specific application.
That is why I also included a proven method for removal of the mixture screw should a screwdriver no longer work on the modified mixture screw if the glue bond fails.
My comments were not theoretical, but rather based on personal experience.
Hope you have butter success over time than I did.
The use of a speedometer cable is more of an experiment to see how it functions. I have had epoxies and JB Weld fail after use also, especially in a torque situation.. I had been careful to not let the epoxy cover the screw channel. If the epoxy fails, and a small screw driver won't work, then an easy-out will fit in the drilled whole for removal. A production model would utilize a permanent bond of some source.
Thanks for the feed back.
 
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