PDA

View Full Version : Any plastic crack repair tricks?



CorrectNickname
11-30-2018, 06:08 PM
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?

ps2fixer
12-02-2018, 10:09 AM
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.

El Camexican
12-02-2018, 03:03 PM
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.

ps2fixer
12-02-2018, 03:13 PM
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.

Gabriel
12-02-2018, 04:02 PM
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.

El Camexican
12-02-2018, 06:28 PM
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.

ps2fixer
12-02-2018, 07:37 PM
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.

newby200x
12-03-2018, 08:51 AM
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/showthread.php/185142-My-experience-how-to-on-Plastic-Welding

COAinPaso
12-08-2018, 12:19 AM
X2 on the soldering iron. Worked on a speaker grate/cover in a ‘92 Chevy pickup I had.

ps2fixer
12-08-2018, 01:49 AM
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.

BOB MARLIN
12-08-2018, 09:59 AM
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.

ps2fixer
12-08-2018, 02:52 PM
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.

jrock454
12-30-2018, 08:54 PM
use super glue and put baking soda on it before it dries makes a super hard weld

ps2fixer
12-31-2018, 04:03 AM
Never heard of that one. Only down side I see to that is super glue isn't flexible, so it would be brittle and break easy via shock, atleast I would think. I guess the baking soda is like adding gravel to cement. Maybe there's different types of super glue though?

jrock454
01-02-2019, 12:16 AM
no the super glue and the bakingsoda have a chemical reaction

ps2fixer
01-02-2019, 02:17 AM
I searched around a bit on the super glue trick, and everything seems to point to that the baking soda acts as an accelerate for the normal super glue reaction. It sets up nearly instantly, and the process is baking soda first, then super glue. Heat is generated in both reactions, but with the accelerate it makes more heat since it's a faster reaction. Neat stuff to know, seems it also helps the super glue bond to surfaces better and such too.

Would be neat for someone to test this on a junk set of plastics and see how hard it is to re-break them. I suspect the flexing would be a problem, but for smaller plastics like headlight housings, it might be a perfect solution. End result is paint able, but it might yellow and cause a slight color change in the paint at the repair location (if it's filling a hole). I know I have a junk fender around, but I'd have to figure a good way to get a nice clean break in it and buy some superglue lol.

oldskool83
01-03-2019, 12:43 PM
i drill a 1/8" hole at the end of the crack. a crack can no crack around 360 degrees. then every 1/4" i type wrap them. not the X stitch, just straight. I go ride then. New plastics are cool if they are too bad.

Steve G
04-28-2019, 12:17 AM
Zip ties. Or, as the kids call them, drift stitches!

yoyosmuggla
06-02-2019, 04:04 PM
I used a 60 thou thick piece of sheetmetal behind the crack. Drilled a hole, put a cleco in it, then started drilling the rest of the holes and riveting them.

258733

Gabriel
06-02-2019, 06:45 PM
Few more rivets and that ATC is ready for a Judas Priest concert!

Probably a very solid repair. :cool:

yoyosmuggla
06-02-2019, 07:16 PM
It looks pretty metal right! Haha

ps2fixer
06-03-2019, 01:39 AM
Not many people think of riveting them back together, works great for sheet metal, so why not plastic + sheet metal =D. Now where to find them Honda Red Rivets.

Mullet_Man
06-28-2019, 02:46 PM
I find zip ties work really well for fenders my 185s fenders are held on only by zip ties works mint