C15 primary chain case level advice

[Chr is]

I have just drained the oil from my 1960 C15 primary chain case.
I popped the drain screw back in and took out the level screw and put 1/4 pint of oil back in as per Haynes manual.
Nothing is coming out of the level screw hole.
I put a small amount more in and still nothing.
I have blown some air in the level screw hole to see if it was blocked and can feel a slight amount of air from inspection cap where i filled it up.
Should i just leave it with the amount I've put in, or keep filling until something comes out of the level hole?
Thanks

[rhyatt]

I can only think that a previous owner has misplaced the gasket and obstructed the oilway at the level plug area.
From memory, the boss or casting at the level screw is partially removed to allow oil out at that level.
Are you able to blow air under pressure in through the level screw??

[Chr is]

I have used a camera lens blower which sits nicely in the hole.
When i squeeze it and blow air in i'm sure i can feel air coming out of the inspection hole where i filled it up.

[rhyatt]

It sounds as though the way is clear for oil to pass through.
Personally, I'd drain it completely and start from scratch, put a known amount in and measure what comes out.
The other option is to look through the central inspection hole when it is running, if oil is plashing, then you know the chain is dipping into the oil and picking it up.
There is a little chain oiler at 3 o'clock that will also drip oil onto the rear chain.
I use ATF in the primary chain case.

[Chr is]

I've drained the chain case and the exact amount came out that I put in the first time which is good.
Oddly though when I took out the drain screw, oil was coming out somewhere behind as I've circled in the picture



I can't work out where although i suspect here is a hole the other side of the case so when i unscrewed it it opened up another drain hole behind???
Once empty I put the drain screw back in but before filling it I blew air in the level hole again and air was definitely coming out of the inspection hole so I'm guessing the level hole is clear.
I filled it up with 5oz as per rupert ratio but again nothing coming out of the level hole.
So I guess as I measured 5oz in I'm going to leave it.
Just to make sure I'm not making a mistake I've marked what I think is the drain screw (1), the level screw (2) and the inspection/fill hole (3)



Thanks for reading

[rhyatt]

Just checked the bsa specs,
1/4 pint or 140cc
Just ensure that when running oil is spashing about when looking in the inspection hole.

[Spaceman]

There is now probably a through hole in the crankcase for the drain screw so that when it is removed, oil will seep out at both ends. Both the level screw and drain screw need sealing washers to keep the oil from seeping past. Unfortunately, this won't stop oil seeping out of the inside end of the through hole which ideally needs to be capped off in some way.

In terms of the level screw, it's possible the entry hole is partially blocked preventing a proper flow of oil out of it. It would be worth over-filling the chaincase to check what happens but, if blocked, you would have to take the cover off otherwise you will have no easy way of checking the level of oil inside the chaincase at a future date.

[Chr is]

Thanks for the advice.

I'm new to the classic world and this bike is fairly new to me, so i'm trying to learn.

I've just run it for a few minutes and it does leak quite a bit of oil.

Since owning it I've known it does leak quite a bit after running.

This looks like its from the hole the other side of the drain hole on the chain case where i said that oil was coming out once i removed the drain screw (in one of my previous images).

Is it that my drain screw is too short and should go and fill this hole completely up on the other side?

Might explain why when i start to remove the drain screw the oil seeps out behind before i've removed it from the front.

Surely this isn't a good way to hold the oil in the chain case?

I've tried to get a picture of it but i can't get the camera in there to take a good picture of the hole behind.

Am i missing a part or something as i think this would explain why i leak so much oil whilst and after running.

[Spaceman]

The rear 5 or so chaincase screws have through holes in the back of the chaincase but this doesn't matter because the gasket (if fitted) will stop oil seeping into the holes. However, I'm not sure whether the chaincase design would allow a through hole for the drain screw (is there a space on the inside or just solid crankcase?) and will need to check on my C15 later. I am sure there would have been a blind hole originally but, if someone has used too long a drain screw, it's possible it could have been turned into a through hole.

If there is a through hole for the drain screw then oil will be able to seep past the screw thread which is why both the level screw and the drain screw need sealing washers on the chaincase side. Again, if there is a through hole, the inner end ideally will need to be plugged to stop oil seeping out and a suitable length of screw then used. To be able to plug a through hole, you would need to remove the chaincase cover first.

[Spaceman]

I've just checked my B40 which will be the same as a C15 and can see the drain screw has a slight through hole - there is just enough space behind the chaincase for a hole to emerge before the crankcase proper gets in the way! I am sure that BSA did not design it this way and so the hole must have been formed by someone in the last 60 years having used too long a drain screw!

If left in this state, chaincase oil will inevitably seep out slowly past the drain screw thread - whether this will matter or not will probably depend on how much oil is leaking out elsewhere from the engine! If the through hole is considered to be a problem, to seal it properly will need the chaincase cover to be taken off. If I was doing the job, I would first work out how much of the hole I could afford to block up (5 mm?) and what length screw could then be used. After degreasing the threaded hole, I would then inject some RTV silicon into the end of it to seal it making sure the required amount of thread was still usable.

[rhyatt]

looking at your picture, I reckon a previous owner has screwed in that screw too far and broken through - as mentioned earlier , clean it up and there are plenty of sealers or chemical metal to rebuild the outer edge as shown in the picture.

I have just finished rebuilding a C15 and got it really oil-tight (which is nice). using ATF which is pink can help you identify where any leaks are coming from.
golden oil from gearbox
pink from primary
darker from the engine

don't forget, when running it was designed to drip from the rear chain oiler a tiny bit of primary oil (located at 3 o'clock with a little pipe attached to go onto the rear chain)

[Chr is]

Thanks for the replies,you guys have been really helpful.
I will try to plug it with some sealer as you both say so that I can enjoy it over the summer.
Might be a bit tricky getting the hole clean and sealed with limited access though.
Then more long term I will take bits apart over the winter.

In regards to the oiler, I've not found it yet and no oil is going on the chain.
I will have a deeper look this evening.

[rhyatt]

I use brake cleaner and a brass wire brush.
That'll bring it up nicely.
The rear oiler is a short 1" long tube into which that 3 o'clock screw goes.
From this little tube is a short 90 degree pipe onto which there may be a piece of piping taking the oil over the rear chain.
They do get gunged up so worth removing and poking clear.
It is also the only place the chaincase breathes through.

[Chr is]

Had a really good look around the rear and can't see anything like you have described as a chain oiler.

[rhyatt]

https://draganfly.co.uk/wp-content/uploads/2020/08/400330-scaled.jpg

Do you have a screw at 3 o'clock??
I'm wondering , if you DO have a screw in there, then what is it screwing into? As this oiler is the "nut" at the back of the chain case.
Is this oil leak you describe emanating from there I wonder??