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  1. #1

    Default Options for missing threads on Super E air cleaner bracket hole

    Referring to the carb body in the pic below, the left threaded hole (at nine o’clock) in the body of my Super E is missing threads. Some are in there, but they are much deeper in than those in the other two holes (these are the holes into which the bolts go that hold the air cleaner backing plate on). By “deeper” I mean it looks like several of the initial threads were somehow pulled out. Not just stripped, the diameter of the opening is actually a bit wider than it should be at the opening. Seriously stripped? There do appear to be decent threads in there, much deeper. Problem is, the standard AC backing plate bolts aren’t long enough to go thru the plate and reach those threads. I was thinking of just trying to find a longer bolt, but there still may not be enough threads to hold a new bolt securely. And I don’t want one of them coming through the carb into the engine! So another option is buying a new body. Is that something I can find used, or do I have to buy it new? Or buy a new carb? Or can I ream out the hole and fill it with an insert and retap? That scares me a bit, because of the possibility of it coming loose and going into the engine.

    Are these my only options? I don’t really want to run with just two bolts, although I suppose I could.

    Click image for larger version. 

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    Thanks,
    Steve
    Last edited by scooper321; 04-06-2020 at 9:28 PM.

  2. #2
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    What is the size and thread pitch? How much 'meat' around the outer edge of the hole?

  3. #3

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    If ya got some threads in the bottom, could you screw in a stud with epoxy/JB weld?

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    Might be a good idea to install one of those screen atomizer's ....
    It has a dual purpose ...

  5. #5

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    Quote Originally Posted by TriNortchopz View Post
    What is the size and thread pitch? How much 'meat' around the outer edge of the hole?
    It is 1/4 inch X 20 X 1/2 inch screw. I could probably use a helicoil Although I am a little worried about whether the hole is stripped wider than the 17/64” hole that the quarter inch Helicoil requires. I might also try and get a couple longer size screws to see how they work.

    I don’t think epoxy or JB Weld will work. I’m not looking for a permanent solution.

    And I have no idea what a screen atomizer is.

  6. #6

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    If you can't simply install a longer screw to catch the good threads (and you must be careful not to bottom a screw in the hole, because a broken casting could result), then I would install a helicoil and call it good. Because it is a shallow, blind hole, you may have to shorten the insert by a thread or two. That is easily done with diagonal cutters. There will be plenty of material in the hole to anchor the helicoil. The problem is the casting will be thin around the hole. I think you would be successful. Get it square.

    Jim

  7. #7

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    Quote Originally Posted by JBinNC View Post
    If you can't simply install a longer screw to catch the good threads (and you must be careful not to bottom a screw in the hole, because a broken casting could result), then I would install a helicoil and call it good. Because it is a shallow, blind hole, you may have to shorten the insert by a thread or two. That is easily done with diagonal cutters. There will be plenty of material in the hole to anchor the helicoil. The problem is the casting will be thin around the hole. I think you would be successful. Get it square.

    Jim
    Thanks. I was wondering how to handle the fact that it is a blind hole and may need a shorter coil. Iíve never used them before and while they donít look difficult, itís good to understand the whole process first. Thanks for the suggestions. And the vote of confidence!

  8. #8

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    You really need to do this in a mill or drill press, and clamp the carb body to the table for good control. Drill to the bottom of the existing hole, but no further. There may be a cross drilled passage, and you don't want to break into that.

    Jim

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  10. #10

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    Quote Originally Posted by JBinNC View Post
    You really need to do this in a mill or drill press, and clamp the carb body to the table for good control. Drill to the bottom of the existing hole, but no further. There may be a cross drilled passage, and you don't want to break into that.

    Jim
    That’s going to be the challenge. I don’t have a drill press. Might have to check out the local motorcycle collective nearby (they rent bays and tools) to see if they have one.

  11. #11

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    Yeah. Trying to avoid dropping $200+ on this. I’d rather find a used one at a swap meet for $50 before doing that. If I spend $200, I’ll replace the carb entirely.

  12. #12

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    could you carefully tap it slightly bigger in (gasp) metric thread?

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    Quote Originally Posted by flatman View Post
    could you carefully tap it slightly bigger in (gasp) metric thread?
    was looking at that earlier today...7mm, a not too common size, but an option, as tap drill size is 6mm = 0.2362"

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    Something like this would be my suggestion. Maybe not necessarily that one but like you said hit up swaps, ask your Indy, marketplace, etc

  15. #15

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    Quote Originally Posted by TriNortchopz View Post
    was looking at that earlier today...7mm, a not too common size, but an option, as tap drill size is 6mm = 0.2362"
    The helicoils for 1/4" bolts that I've seen use a 17/64" drill, which is .2656". So that's a little larger than that. I think I'll try to stay with the 1/4" bolts and use a 1/4' helicoil, just to keep things as standard as possible.

  16. #16

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    Quote Originally Posted by markwade74 View Post
    Something like this would be my suggestion. Maybe not necessarily that one but like you said hit up swaps, ask your Indy, marketplace, etc
    Yup. That's my Plan B, or C, or whatever. If the longer screw and helicoil don't work, I'll either go this route or perhaps try and use a different carb altogether. But as I've rebuilt this Super E, I'd like to stick with it, at least until I determine if I like it or not!

  17. #17

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    Quote Originally Posted by scooper321 View Post
    The helicoils for 1/4" bolts that I've seen use a 17/64" drill, which is .2656". So that's a little larger than that. I think I'll try to stay with the 1/4" bolts and use a 1/4' helicoil, just to keep things as standard as possible.
    Yes, that is a proper repair. Fuck the non-standard hardware.

    Jim

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    Have you tried chasing the threads? It sounds like it may be beyond that but maybe running a tap through there to clean and re cut the current threads could help? Most hardware in 1/4 20 comes in 3/4Ē and 1Ē length. I had this trouble on a Sportster rocker box cover, chased the threads tried 2 different lengths and got one that engaged the lower threads enough that it held fine.

  19. #19
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    I have helicoiled several of these with good result.

    One issue is trying to get a full length thread into the blind hole. Helicoil taps are taper style, great for starting threads and tapping thru-holes but they come up short in a blind hole. I have a second helicoil tap with the tip ground down to a bottoming tap profile. Use the taper tap to start the hole and get as far as possible, then switch over to the bottoming tap to get the thread to the bottom of the hole. Then you can cut the helicoil to the correct length - it should end up about 3/4 thread down from the top of the hole. Don't worry about removing the helicoli tang - it will be at the bottom of the hole and will not cause a problem. These taps do not clear chips very well so make sure to go slowly and remove tap to clear chips often since they will collect in the flutes and cause a real problem if you don't keep them cleared.

    If you do decide to shop for a replacement body be aware that many of them are being sold because someone over-tightened the idle mixture screw and deformed the precision hole in the body. When this happens they are usually impossible to tune and there is no a good repair that I'm aware of. Look very closely with a light and magnifier at the tiny hole in the carb throat - if you see any deformation at all the carb body is likely junk.

    Good luck with it.
    Last edited by 69Glide; 04-08-2020 at 10:52 AM.

  20. #20

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    Quote Originally Posted by brooklynbomber View Post
    Have you tried chasing the threads? It sounds like it may be beyond that but maybe running a tap through there to clean and re cut the current threads could help? Most hardware in 1/4 20 comes in 3/4” and 1” length. I had this trouble on a Sportster rocker box cover, chased the threads tried 2 different lengths and got one that engaged the lower threads enough that it held fine.
    If I understand you, I don’t think that will work. The diameter of most of the hole is too wide to rethread it without a helicoil.

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