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tsiklonaut

a smoky TR280i

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The seal lip should face in towards the crank, any crankcase compression will push against the lip improving the sealing against pressure leakage. As a single seal there will always be a bit of lip movement as in the crankcase there will be a negative pressure before the positive crankcase pressure develops that’s why some engines have back to back seals ( where space permits) to eliminate air being drawn in from the generator side or indeed clutch case oil from the drive side. The first causes a lean mixture...too much air and the second causes too much oil in the combustion process and thus lowered petrol octane and smoky exhausts with poor pick up when the engine is revved up. Main bearings lubed by the gearbox oil under gravity will allow oil to be sucked into the crankcase if the crank oil seal is fitted wrong way round.

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I just fitted as it was. Now thinking about it I think that way it's more correct:

1) there will be some pressure from the oil pouring in from the channels, fitting the spring side away from oil will cause a leak sooner or later (I've made this mistake on forks, they leak every time you do this!)

2) when installing the "other way round" you'll likely damage the seal on installing it (kicking it in from the spring side is a bad idea!)

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Hi Ric, the posted drawing is of the later ball race type inner plate. This bearing does not receive any oil from the gearbox, it is a 2RS, sealed type (which I don't particularly think is the best), the inner plate has the oil feed holes blanked off.

Hi tsiklonaught, If you were to remove the oil seal to fit it the correct way, then yes, it will very likely be damaged, a new one is needed, viton. There is no oil pouring in from the feed holes, it is gravity fed from the gearbox, with the very small movement of oil through the bearing taking place by capillary action and the tiny amount of height difference between the in and out feed holes.

Bye, Peter B.

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On 23/08/2018 at 8:23 PM, b40rt said:

Fork seals don't seem to follow this pattern, if fitted conventionally !

They slide with the fork tube up and down....you know this I’m aware.🙂

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