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CR80 USDs

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I have CR80 USD forks and when I dis-assembled them I found the Base Valve and Mid valve look almost the same, just opposite. They have reversed operation, except for minor differences in shim thickness and port size.

The base and mid valves have similar but opposite setup; each have ports and a shim stack backed up by a spring loaded plate. The spring loaded plates have different hole count and size. Each has 5 shims that deflect on their ID rather than OD. The deflection of each plate is .030, which restricts flow.

Here are pics of the base valve.

ShowaBaseValve1.jpg

ShowaBaseValve2.jpg

ShowaBaseValve3.jpg

My problem is harshness trail riding.

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I have CR80 USD forks and when I dis-assembled them I found the Base Valve and Mid valve look almost the same, just opposite. They have reversed operation, except for minor differences in shim thickness and port size.

The base and mid valves have similar but opposite setup; each have ports and a shim stack backed up by a spring loaded plate. The spring loaded plates have different hole count and size. Each has 5 shims that deflect on their ID rather than OD. The deflection of each plate is .030, which restricts flow.

Here are pics of the base valve.

reminds me of the early XR600 cartridge fork - weird setup...

http://www.supercross-online.de/Z/XR_Gabel.htm

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Not a lot you can do with them, best thing would be to order the base valves for the CRF150 and then you would have something to work with.

Whats your weight and what springs oil etc are you using? For now getting the right spring & oil weights would priority....

doc

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I installed Gold Valves which helped but I still have sharp bump harshness so I did some more measurements. The Mid valve compression is a check valve via a spring loaded plate that lifts only 0.031". I calculated the flow area of the gap at 31 mm2 (the ports area is 48 mm2), to me that doesn't seem like enough opening for good oil flow. So I think the check valve is limiting wheel velocity on compression. I did some part number searches and Honda changed the base and mid valve part numbers several times since 96 which begs the question if Honda replaced them with something more "normal".

The forks are on a XR200 used for trail riding and the problem is harshness on trail debris and tree roots. I have cartridge forks on another trail bike and they are plush compared to these Showa USDs. Rider weight is 175lbs, bike weight is 210 dry, I've used .36kg springs but because of harshness I went back down to .34kg springs. I started with Honda HP Pro Fork Oil 5wt, then lighter Maxima Fork Oil 5wt, and now lighter yet Racetech Light US-1.

More stuff: the rod diameter is 9.85mm, the cartridge ID is 20mm, and the Gold Valve stack is cL5 & cH3:

(1) 17 x .15

(2) 17 x .10

(1) 11 x .10

(1) 17 x .10

(1) 15 x .10

(1) 13 x .10

(1) 11 x .10

(1) 10 x .10

(1) 9 x .10

Thanks

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