The gearbox drain plug on my 1965 B40F seems to have a very thin hexagon, doesn't it? (please see photo.) Or are they like that? Phil.
It doesn't need to be any thicker especially since it's screwing into aluminium. The same with the actual drain plug bolt.
Fair enough, thanks AWJDT. Phil.
I'm having difficulty getting a good purchase on the hexagon to loosen it. A socket is difficult to get on because the casing casting is in the way on one side. So I'm thinking an open-ended spanner, but am a bit worried about damaging the hex, which is not in great condition anyway, and, as I say, is very slim. Does anyone know what size it is (assuming it's original)? It appears to be something like 13/16" a/f. And what is the best tool for undoing it? Thanks. Phil.
Quick answer which might be wrong but 1/2" BS (F or W) and not AF.
Measuring across the flats it might be 7/16 BSW / 1/2" BSF, so I'll need to get a suitable spanner. But getting a purchase will still be difficult, because of a) the casing casting getting in the way of a socket on one side, and not being able to get an open-ender on square. This is made worse of course by the slimnness of the hexagon, which means a spanner easily slips off. Maybe a box spanner (its wall being a bit thinner than a socket's)? Has anyone removed this drain plug recently, and if so could you tell me what you used please? Phil.
3/8 inch drive sockets can be quite useful, 1/2 inch drive often too thick for some of the spaces on our bikes.
My socket ratchet is 3/8" drive, but I don't think even the right size socket, if I get one, will go on the hexagon properly at one side, because of the casing casting being in the way. I am basing this on offering up a socket (13/16" af) that nearly fits the hex. I guess I could buy the right size (BSW/F) socket and try it, but don't really want to waste the money if it won't do the job. There doesn't appear to be room to get an open-ended spanner on squarely either, and with such a slim hex an open ender is very likely to slip off. I don't want to mess up the hex too much. Has anyone actually unscrewed the plug recently, and if so what did you use? Thanks everyone so far. Phil.
Just undone the drain plug on a C15 which should be the same. Requires a 7/16 BSW socket or spanner.
ps. Didn't have any difficulty fitting the socket to the drain plug but it's best to hold it firmly on the thin nut with one hand (to avoid it twisting off) while apply forced to the end of the wrench with the other. The nut is actually 1/2" BSF 16 tpi and the same size as 7/16" BSW as noted.
Thanks very much AWJDT. Regarding getting the socket on, please could you tell me: do you reckon the casing on your C15 is the same shape as on my 1965 B40F? Phil.
Give me 30 mins and I'll try the socket on my B40F but I don't expect any difficulties with the socket fitting. I might even find a mirror and check the crankcases around the drain plug to see if they are identical.
My '67 C15 is slightly different to my '65 B40. In the case of the C15, the bottom of the drain plug casting is proud of the bottom of casting for the gearbox sump which runs horizontally from the drain plug to the right across the bottom of the gearbox. In the case of my B40, the bottom of the gearbox sump projects 1 or 2 mm below the bottom of the drain plug casting. However, the sump casting is milled away to the same level as the drain plug casting to give a clearance of the order of 5mm for the drain plug nut allowing you to get a socket on it.
In that case I should be okay. Thanks very much indeed, AWJDT. I'll go ahead and buy a socket. Phil.
Looks like access to the plug could be difficult - this extract from factory issued parts bulletin G31 of March 1965 shows that the spot facing was increased in diameter to enable a box spanner to be used to remove it.
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.
Here's the photo.
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.
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.
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.
Should not really need it but if it leaks you could use some.
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
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
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.
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.
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.
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.
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.
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?
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.