My 46 SQ4 is finished - or so I thought

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john.davies
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My 46 SQ4 is finished - or so I thought

Postby john.davies » Thu Aug 15, 2019 3:40 pm

After 3 1/2 years of toil and frustration I finished my 48 rigid girder SQ4 a month ago and was ready for test runs and fettling the problems that arose. I have now had a few short rides and fixed a a number of small issues that have shown up but I am stuck on the latest. She has a rather large oil leak that is coming from where the dynamo pushes up to the magneto body. When running there is a stream of oil that flows down over the pick-up and onto the oil pipes and frame. I have checked that the breather is clear. There is very little blow out of the breather when she is running so I don't think that the timing case is pressurising. I am stumped on why so much oil is getting into the magdyno front housing and then leaking out the join between dynamo and mag housing. I was hoping somebody else had experienced the same problem and had an idea on how to fix it.
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Image 1937 Panther M100 Rigid, 1946 Ariel Square 4 Rigid / Girder, 1952 Norton Model 7, 1953 BSA A10 Super Flash (WIP), 1958 BSA C15, 1961 Triumph T120R

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john.davies
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Re: My 46 SQ4 is finished - or so I thought

Postby john.davies » Thu Aug 15, 2019 4:10 pm

I assume that what is happening is that the timing chain is lifting up oil and dumping it on the magneto pinion and it is then running along the shaft into the magdyno front housing where the magneto and dynamo pinions are splashing it around and it finds it way out between the dynamo and the mag housing, There is no gasket where the dynamo butts up to the magneto housing so I guess I could seal that up but why is there so much oil getting in? When I take the timing cover off there is very little oil in there. By the way, it has a standard plunger pump fitted.
Image 1937 Panther M100 Rigid, 1946 Ariel Square 4 Rigid / Girder, 1952 Norton Model 7, 1953 BSA A10 Super Flash (WIP), 1958 BSA C15, 1961 Triumph T120R

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Re: My 46 SQ4 is finished - or so I thought

Postby john.davies » Thu Aug 15, 2019 8:05 pm

Having spoken to Paul Jameson, he suggests that the hole that the mag pinion is passing through may be larger than normal. There has been a repair of the hole in the past and perhaps it could be the problem. The picture shows the engine when I got her and the hole with the repair is still the same, only cleaner. If anybody has a set of iron 4G cases available with a standard size hole could the please measure it and perhaps upload a photo so I can check. Thank you.
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IMG_0001_1.jpg
Image 1937 Panther M100 Rigid, 1946 Ariel Square 4 Rigid / Girder, 1952 Norton Model 7, 1953 BSA A10 Super Flash (WIP), 1958 BSA C15, 1961 Triumph T120R

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Re: My 46 SQ4 is finished - or so I thought

Postby paul.jameson » Thu Aug 15, 2019 8:38 pm

Further to our chat earlier, your photo of the inside of your timing chest tells me that you are missing what C W Waller calls "the all-important flange" around the hole for the magneto shaft. Hopefully someone can provide a photo of this which should make all clear to you.
Paul Jameson
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.

Pete.Silson
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Re: My 46 SQ4 is finished - or so I thought

Postby Pete.Silson » Thu Aug 15, 2019 10:16 pm

This is from a 1946 4G...

timing cover oil lip.JPG


I'll have a look through my other build pictures to see if I can find any pictures from different angles.

Pete

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Re: My 46 SQ4 is finished - or so I thought

Postby john.whiting » Fri Aug 16, 2019 3:41 am

You often get a lot of blowby for a short time with new rings ,pistons and bores....after that it settles down and there is no significant crankcase pressure.

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Re: My 46 SQ4 is finished - or so I thought

Postby john.davies » Fri Aug 16, 2019 8:17 am

Thank you guys. The flange in Pete's picture is definitely not there on mine. Do you have the dimensions of the flange so I know what I need to get made up and perhaps suggestions on how to fit it ?
Image 1937 Panther M100 Rigid, 1946 Ariel Square 4 Rigid / Girder, 1952 Norton Model 7, 1953 BSA A10 Super Flash (WIP), 1958 BSA C15, 1961 Triumph T120R

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Re: My 46 SQ4 is finished - or so I thought

Postby Pete.Silson » Fri Aug 16, 2019 9:54 am

John,

The flange itself is only part of the oil seal mechanism. The inside diameter of the flange hole is such as to give a relatively close clearance with the magneto sprocket. You should find that there is an external thread on the back of your magneto sprocket. As the engine rotates this thread continually draws any oil that gets past the flange back into the timing chest.

I have an earlier 4G engine with similar damage to yours. I have fitted a modern oilseal to the case and machined the external thread on the sprocket to make a smooth sealing surface. I have yet to try this out on a live engine however.

Pete

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Re: My 46 SQ4 is finished - or so I thought

Postby john.davies » Fri Aug 16, 2019 11:28 am

Hi Pete, thanks for you information. Somebody else suggested fitting a modern oil seal so I will look into that as an option. Any info on how you did it would be most helpful. As you are not that far away from me perhaps I could come and see how you did it?
Image 1937 Panther M100 Rigid, 1946 Ariel Square 4 Rigid / Girder, 1952 Norton Model 7, 1953 BSA A10 Super Flash (WIP), 1958 BSA C15, 1961 Triumph T120R

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Re: My 46 SQ4 is finished - or so I thought

Postby Pete.Silson » Fri Aug 16, 2019 12:29 pm

John,

I was lucky, the flange on mine had been repaired previously with an aluminium insert threaded into the timing case. I simple found an oilseal of the right diameter to screw into the existing thread. Whether this will work in practice remains to be seen.

thread.jpg

If you are going to the effort of machining a thread into the timing case you may as well go the whole hog and make an inert to go in it. The picture below is of the remains of the insert I removed.

insert.jpg

Pete


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