How does my A65 breathe?

[VintageBike]

Can someone help me....?

Took my 1966 A65 Spitfire Mk3 out for its first decent run the other day.  Only to find my primary chaincase overfilled with oil after 20 miles or so.  This caused the clutch to slip and a good dousing of oil over the rear left of the bike...

I am pretty confident that I didn't overfill the chaincase. It has been suggested to me that perhaps the main oil reservoir had been overfilled (perhaps due to some oil having wet-sumped before I filled it?).  My question is, if this were the case, where does my engine breathe?  I cannot find any reference to this in my workshop manual.  Does it breathe into the primary chaincase?  If so, then it may explain my problem.  If not, where did my surplus lil come from....??

Thanks

Nigel.

[L.A.B.]

My question is, if this were the case, where does my engine breathe?

Does it breathe into the primary chaincase?

No, the A50/A65 engines didn't breathe into the primary case (as Triumph twins did from 1970-on). Your A65 should have a timed breather on the drive-side of the camshaft, - check your parts manual at the page showing the camshaft detail, you should see the breather assembly parts = breather disc, rotary valve, peg, rotary valve spring, etc.?
There's normally a breather vent pipe from the crankcase in the area in front of the gearbox output sprocket on pre-'70 Triumphs, so I guess the A65 vent arrangement is similar?

If the oil level in the chaincase has risen since you checked it, then the crankshaft drive-side oil seal is probably leaking, allowing engine oil to get into the primary case?  

[VintageBike]

Hi,
it's been a while, but a double knee operation has limited my activities in the garage...  But it seems that the drive side oil seal is leaking.  Does anyone know if this can be replaced without splitting the crankcase? I hope so.....

Nigel

[L.A.B.]

But it seems that the drive side oil seal is leaking.  Does anyone know if this can be replaced without splitting the crankcase? I hope so.....

One method is to drill a couple of small holes (3 or 4mm?) in the seal roughly opposite each other. Then select a couple of self tapping screws of a size that will be a reasonably tight fit in each drilled hole, screw them in, and then pull or lever on the screws alternately with mole grips or pliers and hopefully the seal will pop out?