Author Topic: D/fly g/box front seal  (Read 2332 times)

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Offline chippy

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D/fly g/box front seal
« on: 11 Oct 2012 at 19:38 »
Evening All. Have at last got my bike on the road and it runs really well, apart from the oil leak , I suspect from the felt seal at the front of the G/box. Should I give it a bit of time to bed in or wo'nt that happen, or should I replace or perhaps think about modification. If modification is the best option could someone please tell me what is required.     Regards Eric.

Offline eddie

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Re: D/fly g/box front seal
« Reply #1 on: 12 Oct 2012 at 07:05 »
Eric,
       I guess that Mr Douglas expected the front gearbox bearing would leak as he provided an anular groove outside the seal to catch any oil that was escaping! This groove has a drain port that feeds the escaping oil to the front of the layshaft bearing (and back into the gearbox). Now, this is fine on the Mark series gearboxes as they had a breather hole in the filler plug, but the Dragonfly does not have any breather, so as the temperature rises, any expansion finds the easiest route of escape (often, back up the afore mentioned drain port). This problem is more likely to occur when all seals, etc. are in good order (after a rebuild) as the box is relatively air tight. You could try running with one of the top bolts (Allen screw) removed from the gearchange cover. If this stops the leak from the bellhousing, then lack of a breather is the main problem. A 1/16" hole drilled down the centre of the Allen screw before replacing it, will probably be the best solution (without it being obvious that a modification has been done).
    Regards,
                 Eddie.

Offline chippy

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Re: D/fly g/box front seal
« Reply #2 on: 12 Oct 2012 at 10:17 »
Thanks Eddie! I hopped and guessed you might come up with a possible solution. I'll try it ASP!. Thanks again. Eric.

Offline chippy

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Re: D/fly g/box front seal
« Reply #3 on: 13 Oct 2012 at 11:26 »
Hi Eddie, That felt seal must be letting a lot of oil through because what you suggested did'nt work. I tried it with about 1 1/2 pints of oil  in the box and used a 2mm drill as I did'nt have a 1/6th. the box was barely warm but the oil was very aireated. I suppose the only option now is a strip down to replace or modify the seal. Regards Eric