Gearbox drain plug

[Phil C]

Thanks Julian. I  got a 7/16" BSW (1/2" BSF) socket from ebay, as advised by AWJDT, and it worked. I took the bike for a short run this morning and then drained the gearbox. I think the capacity is supposed to be 3/4 pint, so was disappointed to find there was not much more than 1/4 pint in there. Anyway, I'll fill it up to the level of the tube. On the hex (see photo) there is what I think is an "O" ring? Should this be renewed at oil change as a matter of course? It doesn't look to be very much, if at all, proud of the inside surface of the hex. Also, should the small bolt have any loctite or anything to make it oil tight?   Phil.

[Phil C]

Here's the photo.

[JulianS]

I would renew the o ring unless I was sure it was good.

The small level screws are usually OK with a new fibre washer or a dowty seal washer.

[Phil C]

My small screw didn't have a washer of any kind on it - possibly some signs of a sealant of some kind. I guess I should get one.  Thanks.  Phil.

[Phil C]

My mistake - actually the small screw did have a fibre washer, but it's a bit worse for wear, so I'll replace it. I'll also renew the "O" ring. I assume no sealing compound is necessary with either.  Phil.

[JulianS]

Should not really need it but if it leaks you could use some.

[CJH1953]

Should this have an O ring like in Phil C's post 1/6/2018 (hope you don't mind me borrowing your picture) or a flat face and a fibre washer like the drawing in my parts book and most online offers of part 40-3086?  Mine currently has a mangled O ring plus a mangled fibre washer and guess what it leaks like a sieve. 

Thanks
Chris

[Phil C]

For what it's worth, since I renewed the fibre washer and the O ring I've had no problems with it. It's some time ago now, but I don't remember using any sealing compound. Phil

[Phil C]

To clarify, I can't remember whether I used loctite/ sealing compound or not.  I assume the fibre washer and/or O ring were responsible for the low oil level. Last time I checked the level it was fine.

[Phil C]

Although checking back the last time I checked the gearbox level was I think 23 June 2018, so maybe I should check it again! But the bike is hardly used and I've not noticed a leak there.

[DAVE BRADY]

Hi Phil,

Rather than Loctite or similar, I usually put a couple of turns of PTFE tape on the thread to help seal it but it also seems to help to 'lock' it. A bit of Hylomar would dod the same thing as it is non hardening.  I have found that it is quite easy to over tighten these drain plugs in the quest for oil tightness, especially as the thread is in to aluminium or it is only a small threaded item as with the level plug.

Dave.

[chaz]

as always with joint faces cleanliness and damage is a major thing. the level tube face did get damaged and being under the bike it is in a dirty area so if removed without cleaning around when servicing could trap dirt and damage the face. so, make sure faces are clean and undamaged, the o ring should sit in the groove, note, many suppiers are selling metric o rings that may be different from imperial in diameter and height. as long as its all good it should seal but dont murder it up too tight.
fitting a washer is like "belt and braces" so ok but gives you an extra two faces to trap dirt and leak from.
if the threads are worn then they also will provide a leak point, in which case the ptfe is a solution. loctite provides a sealant BUT needs to be a semi permanent not permanent type and if the threads are too loose may not seal.

as always, dont over tighten to seal, Ive beeen looking at my T100 primary cover, the adjuster plug is always done up too tight to stop leaks, the covers I saw at Shepton last week were all cracked through the face due to over tightening, probably the same as mine. reason for looking for a replacement.... mine leaks and its so tight I cant undo and dont want to force it incase it cracks off completely.

[DAVE BRADY]

Chaz,

I had a pressure release valve that had been fitted without a fibre washer and was well and truly seized in the case.  I had tried everything from 'plus gas' to heat and brute force but every thing was rounding off.  Eventually I found an idea on the 'net'.  Use an arc welder just to flash on to the plug.  This should break any corrosion and help to release the plug.  I decided to try and weld a spanner on to the stuck prv just incase it would need some force but no sooner had I struck an arc the prv came undone with ease.
It might be worth a try.

Dave.

[Phil C]

Sorry CJH1953, I think I may have diverted attention a bit from your original question, which started this thread. Any thoughts for CJH1953 please anyone?

[chaz]

guess what, at the unit today and my problem was a socket cap screw. put allen key in and tapped with a plastic mallet and came undone. have now fitted a fibre washer as it was originally the allen screw against the casing, so hopefully sealed.
as for the question, Im sure the B40 one Ive just done had a groove in  the face so an o ring would fit in the recess. this is where I stated above, that the correct size o ring will sit above the face and seal on the case face. however if there is no recess I would go with a fibre washer.