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Hole between crankcase and clutch case

Submitted by dan_field on Tue, 30/09/2014
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Light Twins

I'm getting perilously close to getting the engine back together on my Jubilee! - but as I tipped it up Inoticed oil drained from the crank case into the clutch case from behing the primary sprocket. I thoiught it was the crank seal but having taken the primary sprocket off I can see two holes in the cases that appear to go from the clutch side to the back of the main bearing.One is at the bottom the other is at the top and this is where the oil is coming through. I have a pair of navigator cases and these holes (which I suspect are tooling holes) are filled in. Should they be open or filled in?

Dan

Submitted by patrick_mullen on Tue, 30/09/2014

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Hi Dan,

I've just had a look at my spare Jubilee cases and there are definitely no holes in the crank case at this point. And no trace of any. My guess is that someone has drilled the holes so they could drift out the main bearing. I dont remember seeing any holes in either of the running Jubilee engines I stripped down earlier.

I think I would block the holes now when it's easy to get at on the bench.

Patrick.

Submitted by dan_field on Tue, 30/09/2014

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Jb weld it is then! I'll take a pic for reference. On the positive side it means it has had new bearings!

Dan

Submitted by dan_field on Tue, 30/09/2014

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Heres the Jubilee, holes at 7 and 1 o'clock

[URL=http://s29.photobucket.com/user/deperatedan/media/001_zpsed2ea8fc.jpg.html][IMG]http://i29.photobucket.com/albums/c264/deperatedan/001_zpsed2ea8fc.jpg[/IMG][/URL]

This is the Navi case, holes at 9 and 3

[URL=http://s29.photobucket.com/user/deperatedan/media/002_zps877571f9.jpg.html][IMG]http://i29.photobucket.com/albums/c264/deperatedan/002_zps877571f9.jpg[/IMG][/URL]

Dan

Submitted by patrick_mullen on Wed, 01/10/2014

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Hi Dan,

The Jubilee holes look very neat and tidy, just like a factory job. In the case of the Navigator it looks more like someone had two attempts to get the holes in the right place. Your Jubilee is a later one so maybe the factory did drill the holes to make it easier to remove the bearing. The latest engine I have is 96805 and definitely there no holes at all - removing a main bearing is not easy at all.

Hopefully someone else will reply with info on their engines.

Patrick

Submitted by peter_holland1 on Wed, 01/10/2014

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I agree. I'm sure the factory never built crankcases with extractor holes. They are a last resort if heat andslamming the crankcase onto a solid wood surface won't work. Hence the holes can be any diameter and any position.

Bad luck that the holes were not totally obscured by the new bearing outer race. Your leak would have been minimal.

Good luck with the JB weld.

Peter

Dan Field wrote:

Jb weld it is then! I'll take a pic for reference. On the positive side it means it has had new bearings!

Dan

Submitted by dan_field on Wed, 01/10/2014

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I'm open to suggestions as to how to fill the holes, JB weld is pretty good stuff, potting compound would be another. If the cases were a bit thicker I could tap the holes and put a screw in there, but they are not and theres not much clearance with the primary sprocket.

Dan

Submitted by patrick_mullen on Thu, 02/10/2014

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I have never used JB weld so I can't really comment but it shouldn't be hard to seal the holes with a chemical metal as the pressures in the crankcase should be small and it is supposed to be a dry sump. Silicone I suppose is another possibility. Yes there definitely is very little clearance around the sprocket. It is possible to remove the sprocket/clutch etc when the engine is back in the frame so you always have a second chance.

Patrick.

Submitted by dan_field on Fri, 03/10/2014

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No room on the other side, the back of the hole is the side of the bearing outer race. If I had a lathe I could make a plug tho.

Submitted by patrick_mullen on Sat, 04/10/2014

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JB weld sounds to be good stuff so should do the job easily. I once used an unknown brand of epoxy resin (called chemical metal I think) inside a Honda monkeybike gearbox and it is still working 100% leakfree more than ten years later.

Patrick

Submitted by bruce_firth-clark on Mon, 06/10/2014

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I've got engine 115386 and can confirm no holes like this - just checked as its apart for rebuild

Bruce

Previously patrick_mullen wrote:

Hi Dan,

The Jubilee holes look very neat and tidy, just like a factory job. In the case of the Navigator it looks more like someone had two attempts to get the holes in the right place. Your Jubilee is a later one so maybe the factory did drill the holes to make it easier to remove the bearing. The latest engine I have is 96805 and definitely there no holes at all - removing a main bearing is not easy at all.

Hopefully someone else will reply with info on their engines.

Patrick

 


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