• SU H6 Carburetor Will Not Decelerate

    I have a 1962 Triumph TR3B with SU H6 carbs. After a recent disassembly, cleaning and reassembly of the carbs the RPM would not return to idle after a load. It continued at an accelerated rate whether under load or at a stop - racing. Only by "goosing" the throttle with the accelerator did the RPM drop, but still not to the proper idle - 600 - 900 RPM (or anywhere close to it).

    I checked that each throttle plate was centered in the barrel, that they closed easily and no "daylight" around the edges of the plate. The carb pistons went up and down easily, dash pots properly filled with the right oil, jet needles centered in the jets and not binding. No vacuum leaks at gaskets.

    After much investigation I discovered that I had two problems: (1) the throttle return springs were not set in high enough torsion and (2) the coupling assemblies on the connecting rod were slipping under load. I could not detect slippage at curb idle by manually manipulating the throttle linkage but under load it seems the connection to #2 carb slipped. This allowed at least #2 carb to remain with an open throttle plate vs. #1 carb. The coupling was just tight enough to respond to "goosing" the accelerator but having slipped it was now out of balance. Also, the shafts are made of brass and over time will score from the connectors, also contributing to possible slippage.

    By torsioning the springs another half turn and tightening the connecting couplings I now have proper carburation. (Note: I also have a slight vacuum leak on #1 at the throttle shaft due to wear. This affects balance and fuel consumption but was not the cause of the "racing" problem)

    I hope this helps someone. I couldn't find a similar discussion anywhere.

    I have attached the Moss plate showing the connectors (66) and the springs (77):

    https://mossmotors.com/triumph-tr2-3...retors-su-h6-1
  • Recent Articles

  • Recent Forum Posts

    ggrant162

    I'm here!

    For the second time (they unsubscribed me by mistake!)

    ggrant162 Yesterday, 11:54 PM Go to last post
    Stan Kowznofski

    1275 Blueprints

    Greetings all,
    I'm looking for the engine blueprints for the 1275 MG Midget engine, anybody know where I can find them?
    Thank you!

    Stan Kowznofski Yesterday, 11:34 PM Go to last post
    Basil

    Re: Citizenship test

    The Federalist Papers were written by Alexander Hamilton, James Madison and John Jay, collectively under the psudonym "Publius". Here's a screen

    Basil Yesterday, 11:34 PM Go to last post
    Graham H

    Re: A type overdrive

    Hi Phil,

    The accumulator cylinder has an O ring that seals it in the casting when I first took it apart the O ring had a large bite out of

    Graham H Yesterday, 11:10 PM Go to last post
    pdplot

    Re: Citizenship test

    84.2%. Missed a couple - 1789 instead of 1787, 26 amendments not 27 and Publius??

    pdplot Yesterday, 10:48 PM Go to last post
  • Recent Blog Posts

    Spit451

    Connections for a 'Service Warning Module' - 1976 MG-B

    I am rebuilding a 1976 MG-B that I purchased non-running. There are a few 'modifications' to the electrical system, particularly in the motor compartment.

    I found a module that is mounted on a...

    Spit451 02-04-2019 12:04 PM
  • Twitter