VF750S 1983 Frame rust
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VF750S 1983 Frame rust

This is a discussion on VF750S 1983 Frame rust within the Technical forums, part of the Caferacer.net Forums category; I need advise on what to to with this frame. It Has rusted a fair bit from the inside and out because of water that ...

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Thread: VF750S 1983 Frame rust

  1. #1
    Junior Member zzxcrozzy's Avatar
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    VF750S 1983 Frame rust

    I need advise on what to to with this frame. It Has rusted a fair bit from the inside and out because of water that has been trapped in the bottom right frame tubing. It has become so thin that at one point there was punched a hole in the steel. I noticed that it was so thin that I could peel the hole larger with my screwdriver. Should I replace the hole section? cut off and get a tubing bent to spec? There is no rust on the outside of the frame and it looks like the inside is only badly rusted at the bottom where the water has been trapped. The left side bottom tubing is not rusted because the engine coolant is flowing there (pretty special for these bikes) There was also some rust in the middle crossover, but It does not look as thin as the other tubing.


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    I was first thinking of filing out a square and weld in a piece, but I think the structure is to weak
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    Last edited by zzxcrozzy; 12-20-2018 at 04:24 AM.

  2. #2
    Senior Member nic579's Avatar
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    You could drill 1/16 inspection holes out from the area for inspection it may just be localised next to the welding vent hole.

    ACF-50 through welding vent holes when done enough to soak interior of tubes to impede rust progression.
    Last edited by nic579; 12-21-2018 at 07:50 AM.

  3. #3
    Senior Member XB33BSA's Avatar
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    looks like scrap
    how do you do that frame wok without suspension or wheels
    are you some kinda savant
    r

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  5. #4
    Junior Member zzxcrozzy's Avatar
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    Quote Originally Posted by nic579 View Post
    You could drill 1/16 inspection holes out from the area for inspection it may just be localised next to the welding vent hole.

    ACF-50 through welding vent holes when done enough to soak interior of tubes to impede rust progression.
    Yes I did some drilling, it looks like its mostly localized around the vent hole. However Im thinking of just cutting away the straight piece section and weld in a new tubing.

  6. #5
    Junior Member zzxcrozzy's Avatar
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    Quote Originally Posted by XB33BSA View Post
    looks like scrap
    how do you do that frame wok without suspension or wheels
    are you some kinda savant
    r
    Its not an option to scrap it, I will have to repair it

    I made the subframe while the bike was on its wheels. The rear shock mount is not welded in place yet, waiting for needle bearings to the suspension linkage. I have been working on this bike for 2 years now, did not discover the rust until now..

  7. #6
    Senior Member TrialsRider's Avatar
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    Splint it, weld it,
    fill the whole damn thing with oil, that should slow the rust down considerably
    ... watch for oil leaks and you will know if the frame is cracking & you will know if your welds are any good.
    Last edited by TrialsRider; 12-21-2018 at 02:19 PM.

  8. #7
    Senior Member irk_miller's Avatar
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    I had a CB750 frame that rusted similarly. I discovered the issue when the bike fell on its own because the tubing around the kickstand tore. I assume you're inspecting the entire cradle.

  9. #8
    Senior Member Cyorg's Avatar
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    You could really complicate your life by cutting away all that ugly stamped steel stuff, but you'd need a frame jig for starters... then you could hack off the tube in question and replace it. Just kidding... life is too short for that kind of tomfoolery. A bore scope might give you some indication how far the rot goes. They are cheap. The 1/16 " inspection holes as suggested will help give you an idea of how bad it is. Just be aware that the burr that the drill bit sometimes creates on the inside might make things look better than what they are. When checking out car frame rot they used to use (and maybe still do) a spring loaded tool with the appropriate tip to determine a go-no go. It was specifically set for the area (thickness) you were testing. It gave a consistent blow, so more accurate than beating it with a pic hammer. You could use a spring loaded centre punch instead, but I would't suggest you fart around taking any chances. There is always Xray, but unless you know someone..... it's easier just to do the destructive testing.


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    I should change my tag line..... its kind of hypocritical.
    Geeto67 likes this.
    "Non urinat in ventum"

  10. #9
    Senior Member Geeto67's Avatar
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    that frame's garbage. junk it. get another one.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

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