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When testing the car for the past couple of weeks, the throttles seemed to open to fast, and slam shut too fast. The initial action of the pedal caused way too much actuation of the throttle butterflies.
This was caused by the linkage levers being in the wrong positions, partly due to the replacement of the ball joints. The new ones, as it turns out, are a bit longer, maybe 1/4 inch each or so. I noticed this when assyembling the linkage last November, but it wasn't until I rebuilt the carbs this month and eliminated all the other related problems that the meaning of this came to light.
As each rod gained new length (which could not be adjusted out with the threads, which were at limit), the next lever "down stream" would be cocked forward a bit. Well, the error is cumulative. However the angle of the top levers can be adjusted quite easily, but they must also be parallel (which is a function of adjustable connecting rod length), which the new ball joints would not permit. The middle rod, even at its shortest adjustment, forced its top lever way too high. Non parallel levers have an action multiplying (diminishing) effect. Which means lots of travel can be given to the downstream rod for the given push of the upstream rod. Not good. This causes the throttles at the other end of this Rube Goldberg linkage to jump open with the slightest first distance of pedal push, and to slam shut with little modulation as the pedal neared and reached full return.
The solution was to measure the adjustable rod length needed with the rod near the greatest tangent to the rotating shafts that it is connected to. (Because of the 75 or so degrees of shaft rotation needed, the rotation is set to actually begin about 5 degrees before greatest tangent).
Put another way, the rods need to be at ball joint centers, the same length as the distance from shaft axis to shaft axis.
The rods were cut down and additional 10-32 threads run down further on them to correctly accomodate the ball joints and lock nuts.
WOW! What a difference! Now we have full throttle actuation with all the fine modulation shifted to the opening end of the action instead of at the full open end of the action (where it was useless).
So, if you have a similar problem of too fast throttle opening, and too fast throttle closing, (which makes clutch operation heck) examine the linkage geometry. You may benefit from a similar modification and adjustment procedure.
All the best.
[ 04-22-2004: Message edited by: Brian N. ]</p>
This was caused by the linkage levers being in the wrong positions, partly due to the replacement of the ball joints. The new ones, as it turns out, are a bit longer, maybe 1/4 inch each or so. I noticed this when assyembling the linkage last November, but it wasn't until I rebuilt the carbs this month and eliminated all the other related problems that the meaning of this came to light.
As each rod gained new length (which could not be adjusted out with the threads, which were at limit), the next lever "down stream" would be cocked forward a bit. Well, the error is cumulative. However the angle of the top levers can be adjusted quite easily, but they must also be parallel (which is a function of adjustable connecting rod length), which the new ball joints would not permit. The middle rod, even at its shortest adjustment, forced its top lever way too high. Non parallel levers have an action multiplying (diminishing) effect. Which means lots of travel can be given to the downstream rod for the given push of the upstream rod. Not good. This causes the throttles at the other end of this Rube Goldberg linkage to jump open with the slightest first distance of pedal push, and to slam shut with little modulation as the pedal neared and reached full return.
The solution was to measure the adjustable rod length needed with the rod near the greatest tangent to the rotating shafts that it is connected to. (Because of the 75 or so degrees of shaft rotation needed, the rotation is set to actually begin about 5 degrees before greatest tangent).
Put another way, the rods need to be at ball joint centers, the same length as the distance from shaft axis to shaft axis.
The rods were cut down and additional 10-32 threads run down further on them to correctly accomodate the ball joints and lock nuts.
WOW! What a difference! Now we have full throttle actuation with all the fine modulation shifted to the opening end of the action instead of at the full open end of the action (where it was useless).
So, if you have a similar problem of too fast throttle opening, and too fast throttle closing, (which makes clutch operation heck) examine the linkage geometry. You may benefit from a similar modification and adjustment procedure.
All the best.
[ 04-22-2004: Message edited by: Brian N. ]</p>
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