Can anyone tell me what brake fluid is in early S1 from the factory as it say on the front master cylinder only dot 5 which is silicone based but if I remember correctly nearly all Nissen and Brembo equipment around in the late 90's was dot 4.

Dot 5 (silicone based) is the correct stuff for your early Buell. Dot 4 and 5.1 is mineral based and more commonly used. More recent Buells use this. Never ever mix Dot 5 with any of the other stuff.

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If your dreams don't scare you, they are not big enough.

As Adam says however we did have some discussion about this before as the seals on the Nissin stuff share the same part numbers between the DOT 4 and 5 bikes.

All my Buells use DOT 4 or 5.1 cos rather than let water collect in pockets, it absorbs it and hence when you bleed your brakes you get rid of all the stuff you don't want.

There is a lot of guff spoken about hydraulics, a Ducati expert told me the other day that no Brembo seals are compatible with DOT 5 as they are natural rubber yet the first S1s and the S2s had Brembo at the rear and used DOT 5

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08 Specialized Langster

Found it...

viewtopic.php?f=8&t=13769

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08 Specialized Langster