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Broken Top Cap (expander) on BMX bike to be given to local less fortunate boys..

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Broken Top Cap (expander) on BMX bike to be given to local less fortunate boys..

Old 06-11-16, 08:02 AM
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Strangelove007
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Broken Top Cap (expander) on BMX bike to be given to local less fortunate boys..

I posted this elsewhere, but was told I should move it. I have a BMX Mongoose 20" Hoop D Bike (R1980WMNT) I am trying to fix up to give to some neighborhood kids who can't afford a bike. The expander (top cap) tightening bolt was lose and the handlebars weren't staying lined up with the tire so I tried tightening the bolt and it appears the expander broke. I looks as if it is made out of some sort of cast material and really isn't very strong. I have attached some pictures showing what happened. One shows where the top cap normally goes before it was broken.

I did a brief look around and can't seem to find a replacement part. I thought of trying to gluing them together with JB-Weld or something, but I doubt that would be strong enough considering the pressure.

Does anyone have an idea of where I could get another one of these, how I could fix the one I have? Any other suggestions or comments would be appreciated. I had a kid waiting for this and unfortunately I broke this right before I gave it to him. Needless to say he's a bit downhearted.

Thanks in advance!
Attached Images
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IMG_20160610_161440.jpg (85.7 KB, 19 views)
File Type: jpg
IMG_20160610_161340.jpg (87.2 KB, 19 views)
File Type: jpg
IMG_20160610_161258.jpg (98.4 KB, 18 views)

Last edited by Strangelove007; 06-11-16 at 08:06 AM.
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Old 06-11-16, 08:05 AM
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Raiden
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Try the pictures again, they're not attached.
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Old 06-11-16, 08:07 AM
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Thanks, I got it right this time....:-)
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Old 06-11-16, 09:13 AM
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I don't think that is an expander plug- just a top cap. Am I correct thinking that that is a standard star fangled nut down inside the steerer? It looks like the bolt just sandwiched the broken top cap down onto the top of the stem- exactly like a standard threadless headset except with a bolt that allows the cable to pass through. Except that bolt, and the threads in the star fangled nut are a bigger diameter than a standard headset. I'm going to venture a guess that this an H10 style cap/bolt, and you'll want to replace it with something like this: La Casa Fork Top Cap - H10 | Transition BMX - but you'll want to look up the H10/M10 standard, and see if it matches that bolt you have left over (quick way to find out what you have, if you don;t know how to measure a bolt- take it to Home Depot- they will have a board mounted in the fastener aisle of male and female dummy screws and nuts, you can see if the bolt fit anything there. If it doesn't screw in easily, see if it looks like finer or coarser thread than the bolts they have in stock). Mongoose is cheap department store stuff, who knows if they're actually conforming to any typical bike standards.

Edit: Ah, here, this is more like that you have: https://www.starcyclespares.co.uk/1-o...yro-3052-p.asp

You could also just pull the cable and run it outside the fork steerer, but some kid is going to expect to be able to spin the fork (because of that rear brake assembly), and break your brake repair, so I'd also replace that rear brake assembly with just a direct cable, in that case.

Or replace the existing star fangled nut with a standard model and top cap, and remove the front brake entirely.

Last edited by Raiden; 06-11-16 at 09:41 AM.
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Old 06-11-16, 05:45 PM
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Originally Posted by Raiden View Post
I don't think that is an expander plug- just a top cap. Am I correct thinking that that is a standard star fangled nut down inside the steerer? It looks like the bolt just sandwiched the broken top cap down onto the top of the stem- exactly like a standard threadless headset except with a bolt that allows the cable to pass through. Except that bolt, and the threads in the star fangled nut are a bigger diameter than a standard headset. I'm going to venture a guess that this an H10 style cap/bolt, and you'll want to replace it with something like this: La Casa Fork Top Cap - H10 | Transition BMX - but you'll want to look up the H10/M10 standard, and see if it matches that bolt you have left over (quick way to find out what you have, if you don;t know how to measure a bolt- take it to Home Depot- they will have a board mounted in the fastener aisle of male and female dummy screws and nuts, you can see if the bolt fit anything there. If it doesn't screw in easily, see if it looks like finer or coarser thread than the bolts they have in stock). Mongoose is cheap department store stuff, who knows if they're actually conforming to any typical bike standards.

Edit: Ah, here, this is more like that you have: 1 or 1 1 8 Bike AHead Top Cap Star Fangled Nut & Hollow Bolt For BMX Gyro

You could also just pull the cable and run it outside the fork steerer, but some kid is going to expect to be able to spin the fork (because of that rear brake assembly), and break your brake repair, so I'd also replace that rear brake assembly with just a direct cable, in that case.

Or replace the existing star fangled nut with a standard model and top cap, and remove the front brake entirely.
Raiden, Thanks for the in depth answer. The second assembly you provided the link is exactly the kind of thing I have on the bike. Not sure if it's the exact size, but it's the right kind of part. I used to live in the U.K., but not now. I will look around town to see if anyone has the part, and if not, I will look online.

I'm not sure how I'll get the old part out, if I need to. I know I'm going to have to disconnect the front brake system, like you said, so I can thread the cable through the bolt.

Thanks for taking the time to help. It is very appreciated. You're going to make a boy very happy.

Regards!
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Old 06-11-16, 05:55 PM
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No problem

I don't see that part around very often, and I've never sold one as a small part in a bike shop (though I've built many BMX bikes that came equipped with them)- you'll have to find a shop that just carries an insane number of small parts, or a shop that specializes in BMX (a rare thing). Don;t mind the european seller in my link, it was just the first link I found with the correct-looking part. Use the same keywords to find a US seller.

Yes, just unhook the brake cable from the brake and pull the housing and cable up through. If you buy a nut and bolt kit like in my second link, and for whatever reason the new bolt doesn't match the old the star fangled nut, you'd knock the old star fangled nut out the bottom of the fork (with a hammer and some sort of steel rod from the top) and knock the new nut back in through the top a short distance.
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Old 06-11-16, 11:30 PM
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Originally Posted by Raiden View Post
No problem

I don't see that part around very often, and I've never sold one as a small part in a bike shop (though I've built many BMX bikes that came equipped with them)- you'll have to find a shop that just carries an insane number of small parts, or a shop that specializes in BMX (a rare thing). Don;t mind the european seller in my link, it was just the first link I found with the correct-looking part. Use the same keywords to find a US seller.

Yes, just unhook the brake cable from the brake and pull the housing and cable up through. If you buy a nut and bolt kit like in my second link, and for whatever reason the new bolt doesn't match the old the star fangled nut, you'd knock the old star fangled nut out the bottom of the fork (with a hammer and some sort of steel rod from the top) and knock the new nut back in through the top a short distance.
I found a guy in town who said he can get it for me Monday. Hopefully it will fit. I was wondering what I was going to do if the old bolt doesn't fit through the new top cap. BTW, do I need to take the front forks off to punch the old star nut out? If so, how would I do that? They look pressed in.

Thanks again for what you've done already!
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