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Technical Rochester 2GC Accelerator pump issue

Discussion in 'The Hokey Ass Message Board' started by alteredpilot, Feb 9, 2024.

  1. So this is the 4th carburetor in a row that we've had this problem with. The accelerator pump not functioning properly. In this case, the piston just doesn't want to travel in the bore. It seems that the diameter of the rubber cup is just too big and it's jamming in the bore. I've purchased multiple kits and they all have the same parts, (blue cup with a spring inside) and I can barely get the cup down into the bore without an unusual amount of force. Once its in there, it feels like its jamming. We had another 2GC recently that was on a car that the guy had freshly rebuilt at a big carburetor house out here. It had the same problem and it had the same parts that are in the kits.

    Any idea maybe where to find a different style accelerator pump or is there something we're missing?

    Thanks in advance for your input.
     
    tractorguy likes this.
  2. bchctybob
    Joined: Sep 18, 2011
    Posts: 5,355

    bchctybob
    Member

    There’s two different sizes; 21/32” and 3/4” make sure that you are using the correct size pump cup. Some kits came with both size cups, some don’t.
    Sometimes there’s corrosion in the bore that causes them to stick, it doesn’t take much.
     
    Moriarity likes this.
  3. Thanks. This set up is 21/32 and the bore is clean as a whistle. Same with the last one we had this problem with.
     
  4. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,789

    Johnny Gee
    Member
    from Downey, Ca

    Polish the bore.
     

  5. with what?
     
  6. RICK R 44
    Joined: Dec 13, 2009
    Posts: 474

    RICK R 44
    Member

    Had the same problem. Turns out the pump supplied in the kit is not the proper pump. I believe this pump you need has a leather cup. I got a couple from a carb rebuilder. If you want more info call me at 705 934 4434 or email me at [email protected]
     
    1oldtimer and tractorguy like this.
  7. Thanks. I haven't been able to find a leather pump around here. Every carb shop I talk to uses the kits with the rubber pumps. If I can't find one, I'll hit you up.
     
  8. Rice n Beans Garage
    Joined: Dec 17, 2006
    Posts: 1,682

    Rice n Beans Garage
    Member

    Check with Performance Carb in Ontario
     
  9. alteredpilot likes this.
  10. hepme
    Joined: Feb 1, 2021
    Posts: 542

    hepme
    Member

    Yep--go get some crocus cloth, do NOT use sandpaper of any grit. Go in circles, not up/down and make sure to travel the full length of the bore. If its a new rebuild, use some lithium grease in the bore for the cup to slide on for the initial startup. Like others said, be sure you have the right pump.
     
    The Magic Ratchet likes this.
  11. I talked to him. He said he couldn't help without the carb tag number, which of course i don't have and I can't find my dial bore gauges to measure the pump bore.
     
  12. carbking
    Joined: Dec 20, 2008
    Posts: 3,738

    carbking
    Member

    The reason carbking wants carb tag numbers (or the stamped number on 1968 and newer carbs) is these accelerator pumps have variables:

    (1) pump cup diameter (discussed in this thread)
    (2) overall length
    (3) compressed length
    (4) type of end on pump shaft

    Between the 2G series and the 4G series there are at least 50 different accelerator pumps.

    As far as suggestions go:

    I know this won't be a popular answer, but make the pump! That is why we have leather pumps, is because I make them.

    Jon
     
    pprather, tractorguy and INVISIBLEKID like this.
  13. bchctybob
    Joined: Sep 18, 2011
    Posts: 5,355

    bchctybob
    Member

    If Jon can confirm that there were only two bore sizes, you could use a piece of .750” round stock to verify if it is the 3/4 version or the 21/32 (.656”) by default.
    Then check eBay. Search “2GC leather acceleration pump”. I found several offered.
     
    tractorguy likes this.
  14. carbking
    Joined: Dec 20, 2008
    Posts: 3,738

    carbking
    Member

    There are only the two that one is likely to encounter; as mentioned 21/32 and 3/4.

    Just for grins, I grabbed a 50 year old catalogue, and 43 different pumps were listed for the 2G series alone.

    Jon
     
    bchctybob likes this.
  15. carbking
    Joined: Dec 20, 2008
    Posts: 3,738

    carbking
    Member

    The ebay search found 3 for the 2GC and 2 of those are not leather!

    Looks like my prices need to increase! ;)

    I have only been charging an extra $15 for the leather pump kits over the kits with the modern chemical pumps that I cannot pronounce or spell.

    Jon
     
    tractorguy and bchctybob like this.
  16. carbking
    Joined: Dec 20, 2008
    Posts: 3,738

    carbking
    Member

    For those who might buy one of these, and have never before used a leather pump, one should place half a dozen drops of light machine oil (neetsfoot, 3 n 1, sewing machine oil) on the leather a few minutes prior to assembly.

    Jon
     
    tractorguy and bchctybob like this.
  17. bchctybob
    Joined: Sep 18, 2011
    Posts: 5,355

    bchctybob
    Member

    Neetsfoot oil works like magic on the leather plungers. I’ve had some that were mighty old and dry but they came back to life after a soak in that stuff. My Dad introduced me to it back when I was playing in Little League baseball, to keep my gloves pliable. Been using it ever since.
     
    tractorguy and carbking like this.
  18. Joe H
    Joined: Feb 10, 2008
    Posts: 1,563

    Joe H
    Member

    I recently had a 2G with a pump not working, I used some 600 grit paper just enough to remove the high spots, then red scotchbrite wrapped around a wooden dowel rod that I polished the bore with. It worked great, the pump ran smooth with no more binding.
     

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