plastic welding

[Tking]

My 85 250sx has a crack about 1 inch long on the back fender.
I've never tried plastic welding and I need some info on how its done or even if it is the right thing to do. I don't want the crack to get any bigger.

[bigworm626]

Welcome! try drilling very small holes side to side & using zip ties. the smaller ther better. Frankenteiner style.

[GoObYdOo]

Seems like a bit of work and im not sure how you would color match it if it is a concern,but you can try this....
http://www.youtube.com/watch?v=j4RECGjEOnE

Otherwise I would go to advance auto or autozone and pick up some plastic "weld" epoxy,it works VERY well,you would bevel the edges just like in that video,but i would recommend drilling small holes at the ends of the crack to keep it from tearing further in no matter what method you use.It will be kind of a stress relief point that will keep it from going further.

[Tippmann98]

I have seen guys run a bead of superglue along the underside of the crack to keep it together. I've also had good luck using a heatgun to melt the edges of the crack and push them together again. It certainly doesn't look professional but it does look better than zip ties.

[Tking]

Thanks for all the info.
At one time I thought I saw a device that looked like a heat gun with a narrow tip that had another nozzle attached to the end (side by side) that you could add some sort of filler rod through the second tip and it would melt in and look like a weld job. I don't know if something like this is still available or not.

[GoObYdOo]

Here try this,found it last night but forgot to post it,it works kind of like a soldering iron,but has natural plastic filler rod that takes on the color of whatever youre welding...might have to get one myself...lol

http://www.rockymountainatvmc.com/productDetail.do;jsessionid=3EFF5B1BA8817A25F82EC4 C25BC4C0FC?webCatId=22&webTypeId=140&navTitle=Tools/Shop&navType=type&prodFamilyId=3540&stockId=48183&ref=gmc

[Tking]

Thanks GoObYOo
That thing looks neat, I think that might just be the thing I need. I'm going to order one.

[GoObYdOo]

No problem!Let us know how it works out for you!

[sweetip2000]

You need to get scrap plastic the same plastic as on the bike. If its oem plastic you need to find a busted up oem plastic same color. I am sure you can find broken junk fenders by asking
around. It takes some time to do it right but it will work.

Get a peice of plastic same color and same type of plastic as what you are repairing, maier and oem plastic are different. So if you have maier plastic you need to repair with a peice of maier plastic. If its oem plastic thats what you need to repair. All plastic must be clean
and washed with simple green using scotch brite pads, like you are doing the dishes.
Only use the scotchbrite pads UNDER the fender where the crack is. CYou can use the red or green scotchbrite pads either one will work. Scrub it clean with simple green, was it off good and dry it. You will need a heat gun and a painters metal spackling blade. Use stainless steel blade. You will need a long pair of pliers and thick gloves or a pot holder.
Turn the fender upside down. Cut a small piece of plastic about the size of the palm of your hand. Hold that piece of plastic you cut with the pliers. Turn on the heat gun.
Use the potholder or gloves to hold the pliers. Keep the heat gun about 8 inches away from the plastic you are holding in the pliers. Turn the plastic if you can to heat it from different angles. Do not burn the plastic. Keep your distance. When the plastic gets like taffy it will weep and start to hang that's when you can shut off the heat gun. Put the pliers down and get that stainless steel painters spackle blade. I like to use a 3 inch blade.
Lay the melted plastic on top of the crack and spread it across the crack. If it doesnt cover the whole thing you need to melt down more plastic. I usually go about one inch
over around the entire crack. This will reinforce the plastic and make it 4 times thicker.
It will also stop the crack from spreading. Let it cool down and dont try to bend it after its cool. Leave it alone. Its repaired. You might see the hairline on the top of the fender.
Best to just leave it. It will still look much better than those scary Frankentrike stiches.
Never use the heat gun near your plastic fenders. Always melt the plastic away from your fenders. Good luck

[Jd110]

This above post sounds like a great way to repair a crack. If I read this earlier I would have tried it, first.
But for those that don't have the same plastic, you can buy plastic sheets at a hobby/hardware store.2290931st scuff back side of area. Then cut pieces to overlap the crack. Carefully heat back side of fender until there is a shine. Lay down I piece at a time and continue to carefully heat area. Don't do it in the sun or on a metal worktop. Concrete or even snow would be best. Turns out like this. 229096It is very flexible and sticks really well on this plastic. Although I tried it on my 69' ct-90 air box and it wouldn't stick.

[Ghostv2]

Here try this,found it last night but forgot to post it,it works kind of like a soldering iron,but has natural plastic filler rod that takes on the color of whatever youre welding...might have to get one myself...lol

http://www.rockymountainatvmc.com/productDetail.do;jsessionid=3EFF5B1BA8817A25F82EC4 C25BC4C0FC?webCatId=22&webTypeId=140&navTitle=Tools/Shop&navType=type&prodFamilyId=3540&stockId=48183&ref=gmc

Unfortunately it says it's unavailable. I've been looking for a plastic welder but haven't been able to see how much they cost generally.

I do like the idea of those plastic sheets. You have a link for them online? It would work better than my frankentrike stitching and my zip ties breaking. On my crappy fenders I don't really care about stitching. But I have some nice fenders I would like to fix small hairline cracks on like around the rack holes and mounting holes. Reinforce it a bit.

[Jd110]

No I don't. Sorry. A friend told me about it

[NeverLift]

http://www.3wheelerworld.com/showthread.php/165358-Help-cracked-fenders-ideas-how-to-repair?highlight=plastic+welding

Read this thread. It shows the welder i use and where to buy one. and some other ideas. Most important this is matching the plastic you fixing with the "rod,stick,chunk" to fill.

[Jd110]

That's great never lift. That seems like the way to go if a person has the money. Your welds looked very good and strong. I did see them when I was repairing big red last year. Just didn't want to dump a ton of money into it at the time. Now I'm a bit crazy over atc's so I'm getting a plastic welder. Thanks

[NeverLift]

That was 2 years ago and i haven't broken one yet. I have been rough on those fenders they have cracked in other places. Some cracks go thru my welds and they hold strong.

[muthey]

I purchased my plastic welder from harbor freight a few years back and have since then performed many welds. the best welds are the ones where there is a bead not a complete melt. I have tried it both ways where I have melted the rod completely back into the material and smoothed it, and they always seem to break that way but when there is a bead like with steel welding they hold up to quite a bit of torture before cracking. Here are some pics of the welding I have done in the last 6 months.229163229164229165

[muthey]

the biggest thing is having clean surfaces to weld and using the same type of plastic. if you do use a scrap fender to make rods out of make sure you scrape all of your rods to nice clean plastic first. then apply a little heat to the start of where you are going to weld , then heat up the first half inch all the way around on your rod. then lay the heated tip of the rod slightly past the start of your crack and weld towards the rod at a slow and even pace down the center of the crack. If possible bevel the edges of the crack, but don't make the material too thin. The rod will flow at it's own rate, try and cut your rod evenly if you can to prevent thin and thick spots and uneven welds. this is alot like gas welding . The harbor freight welder uses heated air that it produces all by itself if you buy the self contained model. I should make a video of doing plastic welding for my you tube channel one of these days. this is the welder I purchased. http://www.harborfreight.com/plastic-welding-kit-with-air-motor-and-temperature-adjustment-96712.html I have read with this model you want to turn it on then let it run with no heat for about 5 min+, and then turn on the heat or it will burn up the element quickly, and the do the reversal when shutting it down and they will last a long time have had mine for 3 years now and still going.

[Dirtweed]

I just need to make tabs for the screws on the bottom of my '82 250R headlight. Wondering if the method that JD110 did would work?