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Like many folks out there, I've had cracked plastic over the years that I tried to repair with epoxy, super glue, wire - you name it. Nothing really did the job or ended up looking decent. We either had to live with a shoddy fix, a broken piece, or shell out the big bucks for a replacement. Recently I found the motivation to look for a better way. This past spring I found that my old push mower had a cracked plastic fuel tank. Pour gas in and gas would pour out. Now, the last thing I want to do is spend my dirt bike money on a stinkin' lawn mower!!!! The tank for that machine was $70 plus shipping everywhere I looked. So with a little research on youTube it was discovered that somebody had figured out how to 'weld' broken plastic. I set to work. Took a couple tries, but I learned some things by doing it.

A couple keys to remember:
- Using an old solder gun, punch a hole through the end of each crack to stop its migration
- Farm plastic material from an unseen area of the part being repaired or from a HDPE bottle or other plastic thing that has some material to spare. I use Tide bottles on my son's KTM shrouds and they work fine.
- Work your hot solder tip into the plastic being repaired but don't go all the way through, I try to burrow sort of a trench and then fill the softened gaps with the farmed material to fill it up and then press it in with the hot tip.
- I found softening up the farmed material with a heat gun can help, but isn't really necessary. It is nice for straightening out curled up pieces though to make them easier to place.

So anyways, on Saturday my beloved and once proud college football team got smoked by the Liberty Flames. I wasn't in the mood for pouting about it so I fired up the KDX for a long shakedown ride in the woods here at our house. Just before dark and literally two minutes from shutting her down I washed out over a tree limb in a downhill turn and the upper mounts on my fairing sheared... on the far side you can see where I had half-heartedly repaired a minor crack I'd discovered a few weeks ago.
A big ride was planned for the following morning with my KDX riding buddy so I knew I had to set to work and get this right. I took out an old broken rear fender that came with the bike and farmed off some material for the job... Next thing was to fire up the solder gun and while I waited for it to get to temp I straightened out the tweaked steel lower mounting bracket... After finishing the work and adding a fair amount of material to strengthen the connections I also flipped the upper brake hose routing bracket and tweaked it some. It has always annoyed me how the hose rode so high above the fairing before bending sharply down towards the caliper. This rerouting really helped hide it from snares and looked a lot more tidy. This winter I hope to upgrade all of my ugly old hydraulic lines when I rebuild my brakes. Got to make her look snazzy since she's going to be lining up against all these fancy euro machines next season! After a full day of HAMMERING at Kairos Resort and suffering my share of drops and oopses my fresh welding job held up to the task. Very satisfying! Having a working head light is nice insurance this time of year when somebody flats deep in the mountains where we are.

My next big project is getting my forks redone. My shock was freshly built last month and oh man it's working great. I rode my buddy's KDX yesterday and I could really feel the difference. He had Travis at Go Race Suspension in Blacksburg, Virginia do a complete rebuild on his shock and forks. They went to the correct springs for his weight and Travis did his 'Belgian Valve mod' along with some other black magic and dark witchcrafts that he brews up special for his KDX customers. I'm blown away by the difference in the two bikes. Mine does have fresh seals and oil, but the valving is stock. When I crank his bike up to speed I can really fell how his bike is eager for more throttle when mine is sort of saying "easy there partner!" His wheels stay planted where mine is sort of chopping across the high spots and giving harsh feed back in the low spots.

When I get ready to this job I'll try to detail the process.

This is a helpful resource. I will definately try this. Had no idea that plastic could be repaired like this. Going to give thjs a go. I tried various epoxies but nothing I tried so far seem to last.

Does this method give crazy fumes or can it be done inside?

I do it inside - it does send up a little tail of smoke, but I turn on a fan and crack a door or leave the garage door open. Just don't stand over it and inhale and you should be fine. I think if you modify the soldering tip into a flat head instead of a point as (I have seen done), that might make it even better. I haven't tried that mod yet.

You did good, Stomper.

Soldering irons are heading in the right direction but the tip is too small.

You can buy specialized soldering irons that have a broader tip but they don't have the temperature control(a rheostat or potentiometer) that allows you to control the heat.

I picked up one of these plastic welders from craigslist for $50. They are great, especially when you have grandkids who break things daily. My son makes fun of me because I weld everything in sight.



Home / Automotive / Welding Systems / Polyvance 5700HT Mini Weld Model 7 Airless Plastic Welder

Thanks for the post and explanation.

Lucy, thanks for your recommendation as well.

You can also find plastic welders that use hot air. I haven't tried one of them because they are significantly more expensive but I anticipate they may give you a deeper heating of the plastic and, potentially, a better weld.

Or, you can use the airless welder on lower heat and, with patience(which I generally don't have), get the same results.

Great info/how to! I love working with metal, but the only thing I've done with plastic is tried gluing or using JB Weld, so it's nice knowing this method as well. Thanks!

Chest protector repair

(the chest protector appears orange because the lens was dirty)

A little more info.

Obviously, I did not show you the finishing steps which makes it look like new. But, I'll do that another day.

As Moonstomper alluded to, the key is to match plastics. Polycarbonate needs a polycarbonate rod, Polyethylene(think gas tank) needs polyethylene rod.

Another key is to be sure your weld goes full thickness so you aren't just joining the outer surface. This takes temperature control to avoid burning the plastic. Smooth, even heat is key.

The welder came with multiple rods for repair and you can also buy them on ebay.

Stomper dun' did good. I probably would have added the steel screen reinforcement for added strength.


Start saving your plastics for welding, boys.....

Thanks for the info, lucy. That company turns out to be not real far from me. I am surprised. It is $177 on walmart and amazon, not real bad for what it does.

Thanks for the screen inlay trick, I’ll have to try that.

Over the Thanksgiving holiday my son hopped on my KDX and was riding wheelies (because he can) when he found out that I had recently misadjusted my rear brake so that it was waaay down there.

He crashed and snapped the 3” tail of my rear fender off. It’s always fun to turn around and see your bike in a heap with your son spread eagle on the ground, then watch as he picks himself up along with pieces of YOUR bike.

Anyways, I repaired it back to full strength and will add some pictures later.

more practice on welding :-)

The screen mesh is readily available from multiple locations. It is usually identified by a number followed by the word “mesh”.

“5 mesh”, “10 mesh”, “40 mesh”. The lower the numerical value, the larger the wire diameter will be. Larger diameter wire will give more rigidity to the joint.

You can also purchase automobile bumper repair kits that use preformed Staples: