ET: Engine (Twin) Persistent oil leak

998cc

Active Forum User
VOC Member
48 Rapide oozing oil? I’ve posted this photo a couple of times, but think it does a reasonably good job of illustrating the porosity that occurs.

This went through the parts washing tank (with solvent), then through 4 sessions of 50 minutes each in a heated ultrasonic cleaner, and then a fairly long session with a high power pressure washer. It appeared to be absolutely spotless until I put it in the oven to heat up for the liner. It was oozing out of the fins as well.

View attachment 34550
That is amazing.
 

998cc

Active Forum User
VOC Member
Get it clean and dry... Then dust it with baby powder. then start it up. If no oil is seen, run it for a 100 yards and back, Still no oil, 500 yards and back etc etc. Got my A twin almost oil tight doing this for the best part of a day!

Hello Robert.
Thanks for the response. That sounds like a reasonable approach. :) I'll try that in the next day or so, and it's a certainty the oil will appear while idling on the stand. :confused:

I have found and fixed a few leaks over the past week. One stubborn one left a few drips on the garage floor overnight. It turned out to come from the tiny screw in the end of the feed quill.

Best regards,
Russ
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
You can just imagine how Mr Vincent felt when sets of C/cases all machined up bolted together, blanks put on all the apertures, then submerged in water and an airline connected to pressurise the C/cases, then they revealed if they were porous or not before filling them up with parts, He had literally hundreds of them until they devised a way to seal them with shellac by putting them in a vat of it and pulling a vacuum sucking out the air then releasing it and the shellac was drawn into the cases. after cleaning and all threaded holes re-tapped yellow chromate was applied on the outside then stoved enamelled, he told me he didn't make much on shadows as the work involved was so much. Typical manufacturer, having a poor product which he had to sell, made in go faster adding a few choice distinctive components. It was certainly an experience meeting him so often as I did with the stem of bananas and an Ltr bottle of whisky, only ever taking a couple of hands of bananas but always kept the full bottle of whisky.
Never painting "D" cases as they didn't require it die-cast.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
sketchy on detail - but a web search may fill in the blanks.

A few years back I had a Yamaha single with an ongoing oil leak. Local dealer identified the problem, Apparently there was a batch of YP250's all with this issue and it was traced to porosity in the heads. The fix was to remove and strip the heads then have them vacuum impregnated with some form of 3M product. My dealer arranged it. Never leaked after that.

I understand Ferrari still do this as part of normal manufacture for their alloy engine castings
 

Phil H

Forum User
Non-VOC Member
Years ago there was a porosity problem with some Norton Commando heads. As I recall, the solution was to blast them with walnut shells to pein the surface.
 
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Cyborg

Well Known and Active Forum User
VOC Member
I don’t know if die casting the cases completely put an end to porosity. I can’t say yet whether mine suffer from it, but there are a couple of voids. Thankfully in areas that don’t matter.

Not sure why Robert suggested baby powder, but best leave that one alone.
For something more manly, you could try something like this.

 

Bill Thomas

Well Known and Active Forum User
VOC Member
48 Rapide oozing oil? I’ve posted this photo a couple of times, but think it does a reasonably good job of illustrating the porosity that occurs.

This went through the parts washing tank (with solvent), then through 4 sessions of 50 minutes each in a heated ultrasonic cleaner, and then a fairly long session with a high power pressure washer. It appeared to be absolutely spotless until I put it in the oven to heat up for the liner. It was oozing out of the fins as well.

View attachment 34550
I would have thought , If the liner fitted right , It would not matter ?.
 

Albervin

Well Known and Active Forum User
VOC Member
Check your rocker oil feed bolts. I have a leak from the front exhaust rocker oil feed that ends up in the places you describe. The new Neal Videan washers have an undersize ID causing a light burr on the washer. This leads to a slight weep which becomes ugly after the oil gets hot.
 
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