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Every 60 to 100 miles I have to add 100 to 150 ml of oil in my A65T 1970 primary case,
Bike is not leaking oil beside the rear chain oil drip,
Any ideas where is my oil going too?
I can't see any connecting holes between the primary and crankcase as on my Triumph 500 and 650.
Thanks


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It will be the rear chain oil drip, block it off and use a chain aerosol on a regular basis.

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the are 5 potential leaks into the chain tunnel ( from the engine side )...( and yeah pic is upside down )
1. the designed chain oiler ( 3 o'clock )
2. the big trapdoor and screws ... to get at the drive sprocket ... ( giant hole in middle of pic )
3. the seal in the center of the trapdoor for the transmission main shaft ... ( not shown )
4. the hole the alternator wires pass-through ( 9 o'clock )
5. the timed breathers exit hole ( 8 o'clock)

start by blocking the chain oiler , or whatever is easiest to get at... and see what happens .
you may want to do a compression check ,
because blow-by can pressurize the primary ... through the crank main seal
increasing the drippage from any of these spots ... and increasing leakage becomes a side effect of poor compression .
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Quinten, the timed breather exit hole is on the other side of the sprocket, opposite the primary case, and will spew engine oil (if, for instance, the crankcase sumps) but not primary oil. All else applies.


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In the sump perhaps?

Is the crank seal bad?


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is the swingarm, rear wheel and fender covered in oil (like mine)? your chain oil drip is working too well.

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Thank to you all for your options and advices,

Yes, going to start with the chain dripper and check that primary chain tensioner (seal and cap),
Rear wheel and fender are oil free (I don't have a chain guard on that bike),
Did a compression test few months back. Hit over 150 psi in 4 or 5 kicks,

Let you know,


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In a healthy enginge, the crank cases have vakuum most of the time. If the crank case seal is sealing only from the inside, it is likely that some oil will be sucket into the cases. Not much to worry about, but you can try to turn the seal the other way round next time you are in there.

Reards


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OLA

no way would the amount of primary oil loss OP is talking about ( "Every 60 to 100 miles I have to add 100 to 150 ml of oil in my A65T 1970 primary case,") be accounted for by a bit of oil mist from primary being drawn into the sump in such a short time ,

as for the suggestion of "but you can try to turn the seal the other way round next time you are in there." ........why on earth would anyone do that when they can get a new seal for $5/10 maybee

BSA got a few details a bit wrong but i think they designed the seal facing the right way


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I partly agree Ignoramus, but where else can the oil go? That amount would make a mess on the outside. I have two A65, and have faced the oil seal different ways on them. The one that seals from the inside looses a little primary oil (not as much as we are talking about here), the other seems quite stable. Both have blocked the chain oiler.

Regards


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BSA and Norton fit the crank mainshaft oil seals to keep the oil in the crank cases, spring side of the seal points inwards. Triumph fit them the opposite way round.

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i fit the DS crank oil seal spring out, in theory if the timed breather does its job, the main case should be below atmoshperic, in practice,it stops working past around 5 K RPM. Either way round is equally/ wrong/ right.
i firmly believe BSA persisted with the chain oiler to mask the drips that inevitably come from the breather discharge.


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I think Gavin’s comment is interesting and worthy of consideration.

My main experience is with Triumphs, but I believe the timed breather system is similar in operation between the marques, in that the breather disc route is only open while the pistons are descending from TDC, and then sealed while the pistons ascend from BDC.

The triangular cutouts in both the fixed disc and the rotating disc occupy 45 deg.

So first opening of the overlapping cutouts happens at 45 minus 45 deg = 0 deg

The maximum overlap for gas flow occurs at 45 deg

Final closing occurs at 45 plus 45 deg = 90 deg

The above are camshaft degrees, crank degrees are double these. I’m not assuming, or suggesting, that this 90 deg cam period exactly coincides with the 180 deg crank period from TDC to BDC.

I’ve never examined the system that closely, my suspicion would be that consideration of gas inertia and momentum would result in a design in which the opening/closing of the breather would be somewhat delayed behind the crank/piston movement. (Somewhat like the way valve timings work).

I can easily imagine such a “tuned system” working well within moderate design limits (in the case of Triumph, designed in 1937 and used till ~1970). But like any valve timing, it has only a range of efficient use. I find my engine is oil tight until sustained use at motorway speeds, then it sweats. I think that breather system is out of its comfort zone at sustained high rpm.
Some of the tuners found this (Stan Shenton, Degens etc). Under those conditions I suspect it will be pressure in the crankcase, not tiny vacuum.


The later breathing system with free flow to chaincase and thence atmosphere solve this issue, but maybe introduce other considerations.

I would say that the timed breather only stands a chance of working efficiently at modest rpm. I don’t think it was ever intended as a vacuum pump, but as an ejector of harmful blowby gas. T140’s don’t leak any more than earlier models.

I don’t think it matters which way the oil seal goes very much, as regards pressure or vacuum either way. Importantly the lip on the seal must bear on the sprocket shoulder intended for it.

My instance is non-standard, modified sprocket with a spacer which fits the seal, I put the seal spring toward the engine, it has worked fine for 20 years, but as said the timed breather has its limitations.

Best of.

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The timed breather makes a great chain lubricator when it is running on song.

I’ve ridden nearly 600 miles to a rally at 70-80mph on the motorway most the way up and not lost any oil. Freed the bike of luggage and some spirited riding later and I’m looking to top the tank up. I used to have a breather open to atmosphere at the same time but I never kept an eye on how much was being blown out of the breather. It’s tempting to block the timed breather off and use the open to air breather (maybe with or without a reed type valve)


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Originally Posted by kommando
BSA and Norton fit the crank mainshaft oil seals to keep the oil in the crank cases, spring side of the seal points inwards. Triumph fit them the opposite way round.

Triumphs share the oil between motor and primary ASAIF ( i really dont know anything about triumph just repeating what ive been told) so in that situation it wouldnt matter a lot would it . BSA dont share the oil

OLA
Maybee a better bet might be to get one of those 2 lipped oil seals ........they are really good but some sizes are a little hard to get ....


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Quote
Triumphs share the oil between motor and primary ASAIF

But when this feature was introduced in 69 they dropped the seal completely, as did BSA when they did the same on the B50 for its introduction in 71.

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yes i did rather wonder why there would even be a seal on a shared oil system Komando


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Originally Posted by kommando
Quote
Triumphs share the oil between motor and primary ASAIF

But when this feature was introduced in 69 they dropped the seal completely, as did BSA when they did the same on the B50 for its introduction in 71.


Best way to go. Large plenum etc.

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I wouldn't think oil from the primary could get into the crankcase even if you took the seal out completely, the primary oil level is a good 50mm below the crank seal, oil will not flow uphill


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Originally Posted by Andy Higham
I wouldn't think oil from the primary could get into the crankcase even if you took the seal out completely, the primary oil level is a good 50mm below the crank seal, oil will not flow uphill
It doesn't have to "flow" -- it is flung all over inside the chaincase. As the inside of the chaincase heats up, the misty, oil-laden air expands and is pressurized. It will find any available path to leave. The only time there is a static pool lying in the bottom of the chaincase is when the engine is shut off.


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That is a hell of a leak rate for it to be mist forced through a seal
100 ml in 60 miles is a veritable flood


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Interesting thread. I wanted to see where this went as I have a theory based on my observations.

Same issue, primary oil disappears. Maybe not but I can invariably only ever drain a lot less oil out than I put in. My bike (69 A65F) is oil tight pretty much.. Doesn't mark its spot, ever, except if I over-fill the gearbox or the primary case.

Ive found there is about 20-30ml residual oil in the primary, fill with 140ml and drain immediately then maybe 100-120 comes out. Run for a while, that is weeks, and unless it's secretly oiling the chain and that's where its going (oiler removed) I get somewhere between 40 & 70ml out.

I run a crank-vent which likely forms a vacuum in the crankcases and the timed breather probably does the same. I had been running a vented filler plug. When I switched to a non-vented filler plug the primary oil consumption went down, but not eliminated.

So my take is, that if the crankcase becomes depressurised or runs under a vacuum oil mist is sucked from the primary into the crankcase. Maybe some small amount of airflow is required for this.

WRT Gavin's comments, oil seal fitted lip & spring on inside of crankcase

Cheers
Ray


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Interesting , thanks Ray. I would not call my primary chaincase oil tight, there is usually a drip at the chain tensioner, but I do not lose a lot of primary oil, with the spring to the outside of the seal oil cannot move from primary to crankcase. I couldnt say what the actual quantities are, I drain the primary every 1,500 miles or so and it looks like the same amount as went in, but blacker on exit.


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A quick update,

I stopped a micro leak by the primary inspection plate, stopped a small dripping by the chain tensioner and plugged the chain oiler,

I filled up the primary to its overflow. Rode 145 miles in city / country. I had to add 120 ml to the primary after that!

I noticed my oil tank is always full (over the 5H mark on the stick) now. I used to add some 20W50 every 500 miles. No need anymore.

I need to change my primary chain (tensioner bolt nearly all in - just 2 to 3 threads left for the cap to screw in), my clutch plates (all 3 springs nearly bottoming in their cups now)…….Plenty of good reasons to open the primary and check/replace the 2 oil seals (clutch back plate, crankcase)………………

Waiting on some parts to get in. Will update about my findings.


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[Linked Image from images.oreillyauto.com]
its hard to find a leak on top of a leaky mess .
Throw some dye in the primary case and go for another ride .

there are different colored dyes that work with or without special glasses and lights .
buy whatever is the most economical choice down at the local auto parts store .
should be under 25 bucks total .

you may find that more than one spot is a leaker .
the dye will be educational even if you are planning a general service clean up of the primary .
as each seal is undone , you'll have examples of seals that are still working and the ones that failed .

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