Author Topic: S6 crankcase pressure venting  (Read 1992 times)

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Offline Kalle

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S6 crankcase pressure venting
« on: 23 Jul 2019 at 14:56 »

Hello
I have a S6 from the 1930s with high oil and crankcase ventilation to the transmission chain. Have read an article on the forum (Subject: S6 crankcase ventilation June 1, 2015). My barrels have been drilled to 0.40 ". The connecting rods have new rollers. I think previous owners have changed the cam gear and the ventilation disc. Sending photos to my ventilation disc and photo from the forum Is there anyone who knows if it is possible to manufacture a new disc with the right dimensions and use the spring and cam gear I have for the drive. Eddie writes that the correct drive should be with 4 small springs but then the cam drive must also be replaced.
Br Kalle

Offline douglas1947

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Re: S6 crankcase pressure venting
« Reply #1 on: 28 Jul 2019 at 17:30 »
Hello Kalle,

I had also trouble with crankcase breathing on my S6, when I bought it a few years ago, always a leaking timing case.
I had checked the breather several times. In the end the mistake was the "missing" hole in the gasket on drive side crankcase to let the brather air free to the chaincase!
I send a photo of a 4 spring breather disc.
But, may be you can use your breather parts, if they will work?

Michael

Sorry, the attachment of the photo to send do not work.

Offline Kalle

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Re: S6 crankcase pressure venting
« Reply #2 on: 01 Aug 2019 at 11:02 »
Hi Michael
Thanks for the tip
The ventilation and strainer in the cover is ok and it is in the channel for the chain lubrication that all oil and ventilation come.
Have lowered the oil level in the engine sump without results.
When I have driven about 50 km and stop, the rear frame parts, rear wheel rim and chaincase is soaked and for a while it runs out about 1-2 food spoon oil on the floor.
One thought is to reduce the size of the tracks of the breather disc
Br Kalle

Offline eddie

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Re: S6 crankcase pressure venting
« Reply #3 on: 01 Aug 2019 at 12:51 »
Kalle,
          The breather disc runs against the inside of the outrigger plate. Now, there should be a seal between the outside of the outrigger plate and the inside of the timing cover (originally it was a cork washer with a ring of steel tube around it to prevent it spreading out). If that seal is defective, gas will be able to bypass the timed breather causing excess oil to be carried over to the primary chain.

 Regards,
                Eddie.

Offline Kalle

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Re: S6 crankcase pressure venting
« Reply #4 on: 12 Aug 2019 at 18:18 »

Hi Eddie,
Thanks for your tip, I have carefully measured the height dimension (5.6 mm) for the tube and added an O-ring and sealing ring as a replacement for the cork ring. Has also put as a test a hose in the plug hole next to oil is pressed located to reduce the crankcase pressure. Unfortunately, that didn't help. Think of reducing the recesses in the ventilation disc if it is the right disc
Regards
Kalle

Offline eddie

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Re: S6 crankcase pressure venting
« Reply #5 on: 12 Aug 2019 at 21:02 »
Kalle,
          Firstly, the extra breather that you have fitted to the top of the timing chest will defeat the action of the timed breather.

          Secondly, the breather disc that you have is not the original fitment for the S6, so may need to be modified to get the correct breather timing. Your breather disc looks to be smaller in diameter than the original. The original was a round disc with a deep groove around the diameter that connected to the 2 breather holes in the face that runs against the outrigger plate. The deep groove has a brass gauze covering it (to help prevent the passage of oil). The back face of the breather disc has 2 lugs to take the drive from the inlet cam, and there are 4 pockets to take the springs that keep the disc pressed against the outrigger plate.

  Regards,
                  Eddie.

Offline Kalle

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Re: S6 crankcase pressure venting
« Reply #6 on: 13 Aug 2019 at 14:06 »
Eddie
Thanks for your reply.
They are probably so the ventilation disc and the outrigger plate have been replaced by previous owners. See in the spare parts list that there is a fault in my engine.
My idea is to try to find out what the area should be on the right disc and reduce the recesses (2pec) with weld in the one I have. The brass mesh is important as you type so that the oil cannot penetrate the disc and out through the outrigger plate.
Winter work in the workshop !!!

 Regards
 Kalle

Offline hoejmark

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Re: S6 crankcase pressure venting
« Reply #7 on: 30 Oct 2019 at 11:07 »
Hello
I have a question that is related to S6/T6 crankshaft pressure venting.

The question is about the Non-return valve body in the T6/S6 crankcase. The non-return valve is placed near to the end of the venting system. When you detach the inner chainguard (the casting one), there is the breather tube with gauze in the crank case, and behind this, the non-return valve body is placed below the venting passage, in a angle drilled hole that leads to the inner crankcase.

I have attached a not - not very good -photo of two non-return bodys. One have a drilled 2,5 mm hole in the cone end and the other have a threaded hole ca. 2 mm. There should be a ball inside and a cap in the opposite end.

What is the purpose of this valve? And how is it to be placed - cone end upwards or downwards?

It seem to me, that the cone end should be placed upwards? That means, that the ball close for pressure venting here, but opens for passage when underpressure in the crankcase. What is then the non-return funktion when it actually opens for return of venting air?

In the spare parts list for T6/S6, the non-return valve has the item no. C/11642 in page 11.

Can someone help about these questions.

Regards Hoejmark

Offline eddie

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Re: S6 crankcase pressure venting
« Reply #8 on: 30 Oct 2019 at 13:46 »
Hello Hoejmark,
                          I think you will find that Freddie Dixon accepted that a certain amount of oil would be picked up by the gas escaping through the breather, so incorporated a drain system to return the oil to the sump. As I  understand it, the gases are mainly controlled by the timed breather and pass through the drilling across the back of the crankcase, depositing most of the oil on the walls of the gallery. At the end of the gallery, there is a return to the sump via the non return valve - thus taking the deposited oil back to the sump and reducing any spillage onto the primary chain. The biggest snag with this system is that any air returning via the non return valve makes the main breather work even harder. From this, I would expect the non return valve to be fitted so that it allows air/oil to enter the crankcase/sump but not escape again. The valve with the smaller hole will probably be the most efficient, as that will raise the percentage of oil in the returning mixture.
    Freddie's breather system works OK but any modification to increase the return to the crankcase/sump will effectively increase the volume of air returning to the crankcase, and eventually expelled again via the timed breather - this will then have the adverse effect of increasing the gas flow through the breather - making it less likely that the oil will be deposited on the walls of the breather - and we are back to where we started!

  Regards,
                  Eddie.

Offline hoejmark

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Re: S6 crankcase pressure venting
« Reply #9 on: 30 Oct 2019 at 19:07 »
Hello Eddie
Thanks so much for your very swift reply.
I think I understand the purpose of the non-return valve now.
The cone end of the body must then be pointing upwards when replaced in position.

Regards
Hoejmark


Offline Kalle

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Re: S6 crankcase pressure venting
« Reply #10 on: 01 Nov 2019 at 13:00 »
Hello
Interesting post from you.
When I switched rollers to connecting rod I found that I do not have the check valve in my engine when I saw in the spare parts catalog that it should be a check valve in the channel.
The engine crankcase has never been apart before me so it is missing without significance perhaps.
I have the wrong ventilation disc in my engine which is the cause of the engine's high oil output.
Cannot find the check valve in the drawing on the oil system in the manual.
Good answer from Eddie and I get an explanation why the hole on the photo goes from the oil canal and possibly check valve
Regards
Kalle