Author Topic: Main shaft felt seal  (Read 155 times)

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Offline Bynorthsea

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Main shaft felt seal
« on: 03 Mar 2019 at 18:38 »
Just stripped my Dragonfly engine to get my crankshaft refurbed, I did so not worrying about draining the gearbox. As a result when I upended the assembly oil poured out into the clutch housing, now when I got the bike there was oil in the case but I was advised not to worry as the gearbox oil level was below the shaft height. Now I have sometime waiting for my new crankshaft I thought it would be good to check the seal. I hoped I was going to be able to pull off the cover plate without entirely stripping the box, not so it seems. Before I do strip the box I'm wondering if I can insert a felt seal through the end of the cover plate and then refit the coupling. In the plate there appears to be a space for a seal and on the splined coupling there is a bearing surface, if that is the case then as it is the currently seal is entirely missing. Comments and advice would be much appreciated.

Offline Bynorthsea

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Re: Main shaft felt seal
« Reply #1 on: 03 Mar 2019 at 18:40 »
Forgot the pictures

Offline eddie

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Re: Main shaft felt seal
« Reply #2 on: 03 Mar 2019 at 20:30 »
The gearbox coupling should be fitted with 2 pressed steel flanges pushed on to the plain spigot - the inner one throws any leaking oil into the catch channel around the input shaft - the larger outer flange covers the outer lip on the front cover plate. There should not be a felt seal in the channel around the shaft - the seal is in the housing that is inboard of the coupling, and is only accessible from inside the 'box. My advice would be - don't worry about the oil loss when the gearbox has been stood on it's front end, it is designed to do that! In normal use, any oil that leaks past the input bearing, gets flung out into the catch channel and drains through a drilling to pass through the front layshaft bearing and back into the gearbox. This drilling also doubles as a breather for the gearbox - so when you stand the 'box on end, the oil returns up the drilling and on to the floor!

  Regards,
                 Eddie.

Offline Bynorthsea

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Re: Main shaft felt seal
« Reply #3 on: 04 Mar 2019 at 08:04 »
Thanks Eddie