Fork failure and repair on a 16

[flypigs]

Today when we loaded up to go to a nearby park, I noticed that the black plastic cap was missing from the left fork tube on my older son's 16" 36v. I looked down in, and saw that the inside of the tube was threaded, but the fork seemed to be secured in the triple clamp.

We had only ridden for 5 minutes when Owen crashed going through some mulch... "Daddy! My moto is broken!" Sure enough that fork tube had fallen out of the triple clamp and the wheel had spun around like the front wheel on a shopping cart. He was fine, and the bike was OK except for the fork. I discovered that on these RST forks, the right tube has a spring in it, but the left tube is only for stability, no spring, no dampening.

I hadn't brought any tools with me, so I zipped home to make a temporary fix. I'm embarrassed to say that I used a hose clamp, a piece of inner tube, and duct tape. It wasn't pretty, but it doesn't carry much of a load, it only has to make sure the fork tube doesn't fall out of the triple.

The last place we had ridden was our yard, so when we got home we made a search of the lawn. I expected to find a metal threaded cap that would pinch the top of the tube into the triple. My wife found the black plastic cap, but nothing threaded. I checked our 3 year old's 16, and found that it also only has a cap. I can't figure out if the tube is supposed to be pressed into the triple, or maybe glued. Does anyone have any idea?

I didn't want to have to wait until Monday to check with RST to see if there is a part that will thread in, so I started looking around the garage. I didn't pull the axle cap from my KTM250, but I think it would have been really close. The RST fork tubes are 25mm outside, and 22mm inside. The thread pitch matched a few bolts I had around, I think it was either 1 or 1.25, so I figured I could find something. I looked in the steering tube of an old set of forks and saw a "star nut" which is what most bicycles use to secure the top handle bar clamp onto the fork assembly. I hacksawed the old tube and pulled out the star nut

That star nut was 25mm across, so I used a grinder to get it to about 22-23mm and pushed it down into the fork tube with a screwdriver and a mallet.

Then I just used the cap that was originally mounted on the star nut, locktited it, and it almost looks like it belongs there.

Again, I don't know how these forks tubes are usually secured into the triple. The top of the triple has a flange that will prevent the tube from pushing through it, but I don't know what prevents the tube from pulling out.

Pete