Mag 21 Repair

[basketcase]

So, in rebuilding my '95 Parkpre, I finally got around to the fork.
This is the second Mag 21 I've needed to refurbish, and doing just a basic clean-up and seal replacement is not a big deal, but this one had a problem........
When I opened it up, I found the plastic adjuster rods just laying loose, inside the upper tubes.
Anyone that's worked on one knows what I'm talking about - The rods are supposed to be threaded into and through the rebound valve, and held there by a little cir-clip in a groove at the bottom of the rod, so they can raise and lower the valve plate, by turning the knobs on the tube caps a partial turn.

Anyway, the bottom ends of BOTH rods had been twisted off at the cir-clip - They were now unthreaded and useless.
After cursing whoever had done this, I had a dilemma - You can't get the parts, and buying another fork would have more than doubled the cost of the bike.
So, after staring at the rods for a while, it came to me, that maybe I could repair them - And this is what I came up with:

I chucked the rods in the lathe, with the threaded ends showing - Luckily, they were made well enough that they spun quite true, even with that much protruding.
I faced the ends off, and then center-drilled them with the size drill needed for a 3mm thread.


Then tapped them for 3mm, very carefully.


And here's the result - With a little washer behind a 3mm socket-head screw, the rods were retained in the valve, and functioned correctly - The screws were held in the rods by thread locker compound, and adjusted to give a full turn of adjustment at the tube caps. You can see one of the original broken-off ends, that the screws replaced.
I don't know if the repair will last forever, but the shock works now as it should, and I'm happy

 

[pictonroad]

Ingenious, great work. Always worth keeping an enormous lathe handy for the odd 3mm tap.

 

[basketcase]

You gotta' use what you got - Actually, it's only my mid-size lathe, the enormous one is in another building

 

[FluffyChicken]

Just to say...
You don't need the circlip part. It used to snap of and rattle around before they moved to the Delrin rods (at some point during the 94 models, my 94 I bought and still have has metal rods. I have others with delrin).

The circlip is there to help stop you unscrewing it all the way out when you remove the top caps.
Useless circlip setup though!, to avoid it when you take the cap off, just keep turning the adjust back in.

Anyway, when all assembled it cannot come out unless someone tries really really hard when adjusting the dials.
(It can pop out like I said when you take the caps off)

Your fix should be good as long as it takes no more space up as it hit the bottom of the outlet stop.(There a gap in the white bit it hits at the bottom)

 

[basketcase]

Your fix should be good as long as it takes no more space up

I checked this, and it should be OK, I think.
I guess that's what caused them to break off - Someone continuing to twist the dial, after it stopped.
OR, someone (NOT ME), twisted the dial along with the caps, as they were unscrewing them