Vintage Dirt Bike Q & A

Does any one know where can get new seals for rear shocks on a 1976 CR250 or CR125 76/77? Trying to restore one. Found a second pair of shocks but they are also bad.
Seems no longer carried?
Thanks in advance for any help.

I've got some Yamaha 93102-11008-00 water pump oil seals here for a YFZ450 quad, they appear to be the correct dimensions for the larger-shaft shocks (12.5 X 25 X 7mm, .5" I.D. x 1" O.D. x .375"), but I have NOT tried them yet so I really don't know. They were less than $5 each.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Ray,

Whats the part number for those seals? I have some blown mr175 shocks i need to fix up.

Yamaha P/N 93102-11008-00.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

These shock seals are under much more pressure than a spinning shaft seal is designed to hold. You need a hydraulic seal. Go to your local hydraulic supply shop. They will have hydraulic seals in stock in 1"od x 1/2" id x 3/8" thick. Ask for poly seals, they work great for shock shafts and they don't have the hard steel outer casing so they will press right into your seal head perfectly. If you had the older 10mm shafts, the 3/8" id seals work great for those too.
Enjoy, Jon

Jon,

I'll try one of these Yamaha seals out at some point and report back. My thought is that these shock bodies (when filled with the correct amount of oil) function mainly as oil reservoirs, and that all the hydraulic pressure occurs within the damper cartridge - the seals' function being just to contain the unpressurized oil. I'm sure I'll find out on the first big bump.

Your post made me think of another thing, though; I wonder if seals are designed differently for rotary and push/pull shaft operation?

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

I think the water pump seal would work. I have changed several and they look to have the same lip design that most oil seals do. Not to mention that they are designed to handle the pressure of the pump itself. These shocks are not pressurized and they are reservoirs in a way but some pressure is going to be exerted against the seal as the shock extends. I might try that off the self seal though on my MR shocks, seems easier to get.

The in out seals are definitely designed differently than the spinning shaft seals. The in/out variety normally has fatter lips and more tension as far as I can tell, especially on the outer lip of a double lipped seal. I've tried the proper size normal seal in forks and been disappointed in unusually short seal life. Good point on the water pump seal, and the non-pressurized shock application. Maybe a good match in purpose. It'd be fun if somebody would drill their old Elsinore shock and install a pressure gauge to see what happens to the internal pressure as the shocks heat up and compress. Any volunteers?

Jon,

I drilled both the shocks and fork drain holes on my CR for Schrader air valves - at age 18, it somehow made perfect sense. I still have the forks, which now use steel caps and stoppers - amazingly, they don't leak at all - but the shocks are long gone (the plan was to mount them upside down and use remote reservoirs, but things didn't work out too well). I remember oil and metal chips coming out of the drill hole when I compressed the shock shaft, but it was more of a 'burp' than a strong jet; oil did come out, though.

On a related subject... does anyone remember Hiiesalu air shocks? I bought a pair when they first came out, didn't like them, and returned them and went with S&W instead.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Well, I finally got the MR (360-type) shocks apart and the seals out. While I have no doubt that seals exist that will fit and keep the oil in, I really don't think I'll easily be able to supply something close to these seals, even special order from a hydraulic supply house. I've been searching the Web for two days now, with no luck at all.

The Showa seals are 12.5x25x13mm 'stacked' seals, with a single-lip exposed seal mounted in reverse on top of a conventional double-lip oil seal w/mounting ring. The top seal fits into a rounded cavity in the shock cap. They appear to be NOK AR7221P seals, zero hits on Google.

I don't know for sure, but I think these may be harsh-environment seals, or perhaps high-pressure seals being used as H.E. seals, or both.

Since the top seal doesn't have a shaft scraper ring protruding through the cap hole as it should, dirt finds its way down and packs in around the outside of the top seal (not a real big deal, as it's not against the shaft). If this seal is replaced with a conventional unit, though, dirt will eventually fill up the cap cavity and form a 'dirt donut' around the shaft and seal face, which in my opinion is just not acceptable. Maybe these seals will last for quite some time like this, but it's still an accident waiting to happen.

I'll be taking the seal to a hydraulic place later today, and post back with what I find.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric