Curnutt Shocks

[Daniel P. McEntee]

I did a search of the forum and didn't find a specific answer to this question. How does the piston come off the shaft of the shock? I got a pair that came with a '77 MC-5 I bought last year and I'm going totry and rebuild them. I need to get the piston off the shaft, so I can remove the shaft and get at the top seal. From what I have read, all the sealing componants are standard parts, and the shafts are in good shape. Just gotta get them apart and figure out oil capacity. Thanks in advance for any help.
   Dan McEntee

[Daniel P. McEntee]

Well, I just sucked it up and twisted on the channel locks a little harder and the piston came loose. Got a small nick or two in the piston side but should not hurt anything with new o-rings. Man, I guess lock tite gets better with age! I knew I couldn't screw up the piston, so just held back on the torque a little. Gotta find  me a better strap type wrench for this delicate stuff. I just found some other stuff on the net. Sometimes I forget google can be real useful!
  Thanks a lot,
   Dan McEntee

[Big Mac]

Try this...it's worked for me. Stick the top eye into a vice with the piston up on top. Find two allen wrenches that will fit as fully through two of the largest holes in the piston. Take your Crescent wrench and tighten the jaws down on both sides of the two allen wrenches. Hold the wrench down tight against the piston and twist away.

Has always come loose and worked well enough to tighten back up later. Sort of disfigures the holes in the alloy piston slightly, but better than mangling the piston itself I believe.

Also search here...should find rebuild instructions with method for filling completely with ATF or oil, heating shock in boiling water and bleeding out excess oil. Curnutts work great for the price, look the part too.

[Daniel P. McEntee]

Thanks Mac. I was thinking pin wrench of some type. but those holes looked really small, and I didn't have anything around here like that. If I have to take these apart again, or find another pair to rebuild, I'll make one. I was using a pair of 24" channel locks, with some plastic wrapped around the piston and trying to be as careful as I could. I'm no 90 pound weakling, as was putting enough pressure to get it to budge, or so I thought. I work on printing presses for a living and deal with stuff like this in all shapes and sizes, and have learned over the years that it's better to sneak up on this kind of stuff if you have to reuse a part again. On the second shock, the mounting eye came loose first. These amazingly simple shocks and I'm surprised no one produces something like this for vintage bikes. Lots of us can't afford 400 to 600 buck shocks just to recreation ride on, and a simple, effective servicable shock like this is desirable in my opinion. Pretty interesting valve thing going on in the inside also. There is a ball check that has beat up on it's retaining pin and they look like they need replacing. The pin is what fooled me at first. The piston was so stuck that I thought maybe the pin went into the shaft. I'll have to figure out the right words and do another search for the reassembly proceedure.
  Thanks again,
   Dan McEntee

[Big Mac]

see http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=7950
and this http://www.thumpertalk.com/topic/615414-rebuild-curnutt-gas-shocks/

[brian kirby]

Works Performance shocks have basically the same valve, Works evolved out of the demise of Curnutt.

Brian