Author Topic: A10 Mystery leak ?  (Read 812 times)

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robin smith

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A10 Mystery leak ?
« on: 01 February, 2018, 08:59:51 »
With a hint of improving temperatures, I decided to drain the sump of my BSA A10 ready for its first outing of the year. After a couple of attempts it fired up and ticked over sweetly much to my delight, that is until observing oil dripping from behind the primary chain case. How could this be, with the sump clear of excessive lubricant?

First, the check for end float on the cam pinion top hat breather . OK!

Next, check the oil pressure release valve. OK!

Then, drop the sump plate and check the ball bearing in the scavenge pipe was clear. OK!

Now I was completely mystified, until remembering the 2 pints drained from the sump and returned to the tank had not brought it up to its previous level! Therefore, where had the missing oil gone?

The answer:
This bike had been parked up on its side stand since last September, with the oil level slowly rising in the crank case until reaching the crank shaft oil seal where it made its way into the primary chain case! Hence, with the engine running the excessive oil was being thrashed around by the clutch and forced out along the gearbox main shaft!

Can you think of a better way of spending a Saturday afternoon?