Is the accelerator pedal on an RN box saloon secured to the control spindle with just a clamping action or does the 'clamp bolt' act as a cotter pin?
Looking at the factory List of Spare Parts, publication 888, page 24, the accelerator control spindle (BF36) would appear to have a notch in the end suggesting that the bolt (BF34) fixing on the accelerator pedal (BF1) is actually a cotter.
My accelerator pedal is marked 1A 140 and has 2.5" total throw. I'm wondering if there were several pattens of accelerators over the course of the production run and if so what differences might there be in excursion/throw - i.e. is there another lever with more movement in it than mine?
I guess you are not getting the carb butterfly fully open, so thinking the pedal is too short.
If all the parts are standard, there should be enough movement to work the carb.
I had this problem, it was caused by the hand throttle lever slipping round the control tube and the linkage then stopped the accelerator pedal moving through the correct arc.
If you look at the bolt side of the pedal you will see that it is slotted and the bolt closes up the slot to clamp the pedal onto the shaft. With the bolt slack the pedal can move on the shaft quite a bit, the procedure is to hold the pedal up against the floor whilst tightening the clamp bolt/nut for which you need three hands. If you tighten the clamp with the pedal down then you will not achieve full throttle opening.
In my case, I have an SU carb on my RN and the butterfly would not open fully when adjusted to be fully closed, and vice versa. The throw of the throttle linkage was not enough to complete the full arc required.
I could get it to idle nicely but it was not too keen on hills or the traffic light grand prix!
My solution was to weld about 3/4" into the short part of the pedal below the footpad, thus increasing the pedal movement. Problem resolved immediately!
I found on my RK saloon that the adjustment of travel on the accelerator was very critical. With the linkage adjusted as Dave suggests then the travel is exactly correct to go from fully open to fully closed. Someone must have done some careful design work! It was exacerbated by play in the linkage, especially the crude 'bent rod' section up to the carburetor. I have replaced this with ball joints at both ends and a spring from throttle lever on the carburetor to the lever on the cross shaft beside the rod. This eliminates any play and ensures the throttle closes fully.
Carpet under the pedal will prevent full throttle being attained.
As a diversion I have done the same thing with the ignition advance-retard lever. I have a spring between the lever on the end of the steering column to the lever on the carburetor. Without it the distributor can wobble quite a long way and introduce timing scatter.
