1929 additional throttle linkage on driver side help

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  • December 9, 2025 at 7:03 am #481822
    Author nameAuthor names are only available to PAS members.

    Good morning, a mechanic friend of mine and I are working to get my restored 1929 seven-passenger running after several years sitting in my collection.  We have cleaned the fuel and cooling systems and run the car in the driveway but noticed an issue and I don’t have the resources to sort it out.  Hoping for some help here after trying to search old threads.

    I’ve attached a few photos.  The throttle linkage to the carburetor has a cross shaft so that on the drivers side of engine there is additional linkage ( in addition to the carburetor on the PS).  Sometimes- not always- when pumping the accelerator the linkage at the green circles gets stuck at the green circles.  It has to do with the rotation of the entire assembly, including the red-circled portion.  At other times the assembly isn’t stuck on the housing but is nevertheless sufficiently out of adjustment and causes a high throttle/idle.

    We are mechanical minded but simply don’t know what function these are serving and notice several points of possible adjustment including a set screw on the silver vertical rod.  Has anyone encountered this?  The stuck throttle of course allows the engine to rev high which is dangerous to drive as well as being undesirable when the engine is started cold.

    Thank you in advance for any help!  The car is stock save for an electric fuel pump used when the pump is empty only.  We are anxious to be able to take a safe test drive.  The car has only been driven a few miles since total restoration in ending in 2017.  Startup oil pressure/idle/charging seem perfect except for this accelerator issue caused by the assembly.

    Thank you- Nick

     

    December 9, 2025 at 12:51 pm #481823
    Author nameAuthor names are only available to PAS members.

    This is the linkage for the hand throttle to fix an increased rpm without the foot pedal. It is operated from the RH lever on the steering wheel hub. I am familiar with the later model Pierce that used a push-pull wire in a flexible tube rather than this bell crank mechanism, but basically with the hand throttle lever in the disengaged position (down) the rod coming up from the bottom of the steering column should just slide up and down the ring of the bellcrank arm without engaging at all regardless of the foot pedal position. The clamp with set screw engages when the hand throttle is set. It’s position should be adjusted so it doesn’t quite engage the ring with the hand throttle lever on the steering wheel in the closed position and the throttle lever on the carburetor is sitting on the minimum idle stop (no choke fully warmed up).

    The bellcrank arm is swinging with the foot pedal motion and is apparently scraping against the shiny bit that appears to be a clip (?) Holding the oil filler cap closed? Something is wrong with that, there should be no interference with the bellcrank motion as the foot accelerator pedal is operated.

    December 10, 2025 at 6:43 am #481824
    Author nameAuthor names are only available to PAS members.

    Jim-  thank you so much for a thorough reply!   It’s a little unusual that I wasn’t conversant on the operation of the hand throttle, but I’m afraid I accumulated a sizable little collection over the years and as it happens sometimes I have not given the PA enough exercise.  Your description is exactly what we needed to sort it out for safe reliable operation.

    The shiny bit, incidentally, on the oil cap is just the light reflecting on the black paint.  For the benefit of the forum members when we adjust it all we will rely back for posterity.   Thanks again! -Nick

    December 12, 2025 at 7:13 am #481833
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    Update:  we investigated the hand throttle with throttle closed and found it operates as we now understand it is designed.  The closed throttle position on the wheel gives complete accelerator pedal travel.  Wheel closed position is 3:00, marked as such.  Moving it down gives us increased throttle to about 6:30 position.  Moving it anti clockwise to noon gives us little effect.  We cannot replicate any movement to catch the lever on the oil cap, which is great.  We had the starter on and off several times including cleaning the commutator, so perhaps had stuck the rod inadvertently.  Many thanks for the help from Jim on the explanation!

     

    We drove the car yesterday after some fuel and cooling work and some pre-oiling under cranking, it ran beautifully and was quite a thrill for my mechanic and me!    -Nick

     

    December 12, 2025 at 10:58 am #481834
    Author nameAuthor names are only available to PAS members.

    Great, glad to hear it. Enjoy!

    December 17, 2025 at 6:12 pm #481881
    Author nameAuthor names are only available to PAS members.

    To add to Jim Chase’s explanation, you can remove the horizontal link completely and the foot throttle will work normally.

    The bell crank assembly that bolts to the top of the transmission bell housing is often in need of lubrication.  Also the link with the roller that comes through the floor and carpeting often will drag on the opening in the floorboards, or on carpeting.

    Adding an additional or changing to a slightly stronger throttle return spring is often done to overcome the friction in the linkages.

     

    Greg Long

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