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Thread: Any plastic crack repair tricks?

  1. #1
    Join Date
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    Any plastic crack repair tricks?

    First post! joined a few days ago, really interested in educating myself with all your guys knowledge.
    Any chance, does or has anyone repair plastic cracks and it looked good? Also seat pans? anyone remake them?

  2. #2
    Join Date
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    The metal seat pans I don't think anyone recreates, but I think I might have seen some of the plastic ones reproduced. Can't really help with the actual details though.

    As for broken plastic repairs, the zip tie "stitching" method works and looks "ok" but clearly is visible and not smooth. There's a process called plastic welding, but you need filler plastic generally, so you'd need to source plastic of the same color to make it look right. After it's welded back together, it's a bit of work sanding it back down flat, and then sanding down the scratch marks to the point where it looks good again. I have a 250es that was repaired using this method, but either the special iron they used was too hot and burnt the plastic and discolored it, or they used like a black plastic as a filler.

    Also, it's worth mentioning that aftermarket plastics can work alright too if they are made for the machine you're working on. It won't be 100% perfect OEM matched since OEM was injection molded, and the aftermarket uses a cheaper process called vacuum molding.

    Hopefully this was the info you was looking for. Should be able to search some of the terms I used to find examples of them, if you can't find anything, let me know and I'll poke around for examples.

  3. #3
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    I welded a few plastic snowmobile hoods in school a zillion years ago. It’s not something you’d nail on the first try and maybe not ever if you were looking to repair your cracks in a manner that would resemble “like it never happened”

    You might want to look for an uncracked, but weather beaten set on eBay. Most plastics can be sanded and polished to look almost new if you’re willing to take the time to do it right.
    Nico Suave.... be part of something bigger

  4. #4
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    To add to the above reply, from my understanding, the sun rotting / brittleness is caused just at the surface layer, if that layer is removed, the plastic won't be nearly as brittle. Kind of like scoring glass gives a spot for it to break along, just it's plastic and it's more of a spider web everywhere.

  5. #5
    Gabriel's Avatar
    Gabriel is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    The trick to making the repair hold is to use a heat gun and force a wire mesh into the plastic on the under side. I use scrap fenders cut into strips for filler rods.
    Weld the crack, force the (I use chicken wire) mesh into the underside and weld over the whole thing. Both sides.

    Then you can sand smooth and polish.
    Last edited by Gabriel; 12-02-2018 at 04:26 PM.
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  6. #6
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    Quote Originally Posted by Gabriel View Post
    The trick to making the repair hold is to use a heat gun and force a wire mesh into the plastic on the under side. I use scrap fenders cut into strips for filler rods.
    Weld the crack, force the (I use chicken wire) mesh into the underside and weld over the whole thing. Both sides.

    Then you can sand smooth and polish.
    Perfect! We used to cut strips out of brass tube to use as welding rods to weld the very same tube in order to get the same color. Never even occurred to me to do the same with plastic as we didn’t have extra parts laying around. That was the hardest thing, figuring out what kind of plastic we had and then trying to match the color.
    Nico Suave.... be part of something bigger

  7. #7
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    Yea matching plastic type and color is a big part of plastic welding. Forgot to mention a broken up fender could be used as the filler. Pretty sure the fenders are ABS plastic, but it's been a while since I was reading about plastics, recycle processes and such.

    You can plastic weld with a solder iron, temp controlled is ideal so you don't have to worry about burning the plastic. The proper tool of course is best, but unlikely you're doing it all the time to warrant the specialized tool. You'd probably want to perform the welding from the bottom side, but you might have to do both sides, can't remember for sure.

  8. #8
    newby200x's Avatar
    newby200x is offline At The Back Of The Pack Arm chair racerAt the back of the pack
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    Here's the link to my process of plastic welding. It's near impossible to get perfect to the point you can't tell a repair is made, but it's better than zip ties in my opinion.

    http://www.3wheelerworld.com/showthr...lastic-Welding

  9. #9
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    X2 on the soldering iron. Worked on a speaker grate/cover in a 92 Chevy pickup I had.

  10. #10
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    Probably worth pointing out, different plastics have different characteristics. Generally plastic welding is related to ABS plastic. I'm pretty sure atv fenders are ABS. The super hard plastics might not melt together well, or the melted seam might break easy, but generally ABS holds up fairly well. ABS is used for injection molding, so its quite literately melted into the part shape to start with.

    Quick google search says ABS starts to melt around 105C or 221F. Soldering irons generally run 300-400C+, that's why I suggested a temp controlled one if at all possible.

  11. #11
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    I believe most ATV plastics are Polypropylene or Polyethylene. If they were ABS you could use the glue for ABS sewer pipe from Home depot and make a "putty" out of ABS sawdust and ABS glue to repair the cracks. That's the method I used to repair a slice in my RV water tank and its held for years now.
    ABS or PVC glue ( or solvent) will not work on Polypro or Polyethylene because they are not solvent reactive based plastic.
    Last edited by BOB MARLIN; 12-11-2018 at 09:51 AM.
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  12. #12
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    Yea forgot to say I don't know plastics well, I've only seen a lot of stronger plastics like computer tower faces are made from ABS, so very possible I'm wrong on the ATV plastics.

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