Showa Shock piston question.

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4/9/2019 4:59 PM

Does anyone know the secret to easily getting a new shock piston ring/band on a Showa shock piston? I am talking about the OEM style not the split Race Tech style. Any help would be appreciated. The bike is an 06 RM250 if that matters.

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4/9/2019 6:20 PM

Warm the piston band up slightly using a hair dryer. This will make it slightly more pliable. With the shock shaft/piston upright in a vise, place one side of the piston band in the piston grooves (with new o-rings installed) and firmly stretch the piston band the rest of the way over the piston. It's easier to do this when your piston/shims are assembled on the shock shaft assembly as you can get a good grip on it with the assembly in a vice. The next step after you get it installed is the most important. The piston band needs to be "shaped" and seated onto the piston and have it's O.D. corrected. Do this by placing the shock body (no oil) in a vise and insert the piston into the shock body and twist/plunge the shock piston in the body. You are essentially using the shock body as a forming tool. Showa actually makes a special forming tool to fully seat the new piston band onto the piston but the above method works fine. Failure to fully seat the piston band makes the shock very sticky and not function correctly. I've even seen it pretty much bind the shock up. As you "seat" the new piston band, measure the O.D. periodically and you will see the diameter fall within the spec limits and the piston/ shock body movement will feel correct as well. Good luck!

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4/9/2019 7:18 PM

Thanks for the tips. I ended up warming the ring in some hot water. That helped a ton as it made the band more pliable. I then used a fork seal bullet to help guide the band and keep it from getting torn up on the pistons sharp edges. I lubed it all with shock fluid and it went pretty easily. After it was on, I used a small piston ring compressor to resize the band enough to get it into the shock body.

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4/10/2019 6:20 AM

Perfect! Sounds like you got it handled.

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