Little brass thread inserts in plastic -- How to fix


snydes

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#1
I know @Philip had pre warned me about these with his review some time back, but here is an example why these (for lack of a better term) suck. Cleaning up the bike and noticed that both of the rear most back fender inserts were pulled clean out. Not sure why, I don’t pick the bike up by the fender to put it on a stand and it didn’t take any impacts so I’m at a loss there. Went to remove it from the subframe and the center screw was just spinning so I had to pop it out to get the fender off. These little inserts are a little too fragile IMO. Definitely an area for future improvement. 49607CCB-F880-46DD-84AE-C7F1193A04B8.jpeg AB714BC0-C70A-4229-A713-CEA2D7F08D0E.jpeg 07F2E43D-E3D7-4C0B-8657-16AC0AEEC740.jpeg

Anyone else have this issue or am I just lucky?
 

Philip

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#2
I screwed up one of these myself, but the rest were pretty much like yours when I got my MX (it was a dealer's demo and had a few miles on it). I agree, this is a very poor design. They spin and they pop. That might work on an iPhone but not on a racing machine.

And your MXR is barely a month old! And, unlike my MX, the original plastic has never been off of it. That's disturbing.
 

snydes

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#8
Sorta. There are grooves and serrations on the insert and the hole left in the plastic is chewed up so essentially you are filling those spaces with an epoxy that locks things back in place. I can’t say yet if it will hold up in this application but I have had a lot of good luck saving the unsaveable with JB Weld. Everyone should have some in their inventory.
 

snydes

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#11
Update on my repair...

I've been monitoring my repair after every ride. I've been doing MX tracks and until yesterday the repair had held. My ride yesterday was uneventful, no wrecks, nothing unusual. I can only assume that there is that much flex in the subframe/fender assembly to cause them to pop apart.

Has anyone else had this happen or am I the one and only? I have a different repair idea in my head I might try, I hate to buy a new rear fender to just have it happen again.
 

rayivers

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#12
Wow, a JB Weld failure - it must be the plastic, which can be a weird material to adhere to.

Heli-Coil makes oversize inserts for correcting tapping errors, and also Twin-Sert double inserts (one inside the other) to to the same thing. These might be worth looking into if there's enough plastic to hold them. I seriously doubt a glued-in large(ish) diameter screw thread will ever pull out or unscrew.
 

Philip

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#15
They work well on the KTM/Husky. But you need a small and long hole in the plastic to screw them into. On the Alta, once you remove the brass pieces, there is a large cavity and a thin plastic at the bottom of them. Not much to screw into.
 

snydes

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#16
They work well on the KTM/Husky. But you need a small and long hole in the plastic to screw them into. On the Alta, once you remove the brass pieces, there is a large cavity and a thin plastic at the bottom of them. Not much to screw into.
Unless you get creative and remove the insert completely and fill the void with an epoxy product. That is exactly how I repaired the two rearmost rear fender attachment points on mine.

Additionally, to help keep the epoxy from pulling out of the hole I drilled some small 1/16” holes on the (inside) exposed sides of the insert boss. Doing that lets some epoxy “spooge” out the holes and provides a bit of an anchor. Then I drilled an appropriate sized hole straight up through the fender and got into a little of the actual plastic. The screws I used were the type that @Scooter584 posted.

So far it has held up to substantially more abuse than the OEM brass inserts did.
 

Philip

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#18
Then I drilled an appropriate sized hole straight up through the fender and got into a little of the actual plastic. The screws I used were the type that @Scooter584 posted
So you screwed partially into the epoxy? Isn't it usually brittle?

I am thinking hot glue might be a better material, but I do not know if it would stick to plastic.
 

snydes

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#19
So you screwed partially into the epoxy? Isn't it usually brittle?

I am thinking hot glue might be a better material, but I do not know if it would stick to plastic.
I drilled all the way through the epoxy and through the thin remaining floor of actually plastic. There are actually two small holes up through the topside of my fender now. The screws ironically were the perfect length and stopped just short of protruding out, otherwise I would have cut them down flush. I was able to still use the tiny little OEM spacers over those screws as well. Maximum length would be optimum in this less than ideal situation.

Yes, you are right, most common two part epoxies are somewhat brittle. I used this JB Weld plastic product I already had laying around, it seemed more flexible than a regular epoxy. If I didn’t already have that product I would have just tried ordinary JB.

Off the top of my head I think hot glue may be too gummy, but there is no harm in trying.
 

Scott

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#20
I too am experiencing the brass inserts pulling out of the rear fender (I will spare you the picture). I also noticed that the subframe brass inserts on the right side are cracked. Not sure why/how this is occurring but I am disappointed in the durability of the plastic. I have only 7 hours on the bike and it looks like it will not be long and I will need a new rear fender and possibly a subframe. I hope they revise the plastic soon and replace it with something a bit more dirt bike worthy.

While I am on the topic of plastic, the side number plates are also very flimsy as they have no subframe support behind them. My right side is already showing signs of cracking. On an ICE bike, one side had the muffler to support it and the other side met up with the subframe. I really don't what to have to keep buying new plastic all the time. On my last bike the plastic would last for years.
Alta Subframe.jpg