Oil tank

Information relating to the Matchless G15 or AJS Model 33 750cc twin. This also includes the G15 Mk II and the G15/45
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Re: Oil tank

Postby Duncan » Wed May 04, 2016 9:38 pm

Peter, the breather feed in the picture comes from the back/top of the tank and is a "mist" type feed not a pressure feed that the spigot would provide.

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Re: Oil tank

Postby Peter Morris » Fri May 06, 2016 3:48 pm

Yes Duncan, I would have thought that a pipe from the return side would deposit far too much will on the chain, but what do I know?

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Re: Oil tank

Postby John Donne » Mon May 09, 2016 9:53 am

That extra oil pipe on the oil tank, from the oil return feed, is the oil feed to the cylinder head rockers. The oil tank is from the earlier models of Atlas Scramblers, G15CS, N15CS, G15Mk2, and G15CSR, and 33Std from 1963 to 1965. For the 1966 Norton twin engines the oil feed was then changed to a pressure feed from the timing cover to the cylinder head. The oil pump had the gears changed to a six speed, there were oil holes drilled in the con-rods to spray oil onto the cylinder walls. The rocker spindles were changed to smooth and not scrolled ones, and the oil feed hole to the crankcase and junction block were changed to a larger diameter.
The earlier oil tanks had a straight bracket that connected to the frame, and the tool box also had a bracket that was bolted to the frame. The dual seat was then changed to a narrower design in 1966, so the oil tank bracket was bent so the oil tank could be pulled in more, and the battery box, tool box had the bracket deleted, and was replaced with a nut, bolt washer and spacer arrangement. Simple really

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Re: Oil tank

Postby Peter Morris » Mon May 09, 2016 4:14 pm

Thanks Anthony, I knew you would know the answer... I thought I'd have to ask you at the next Ardingly show.

Peter

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Re: Oil tank

Postby John Donne » Mon May 09, 2016 5:25 pm

The other pipe that is shown in the picture is for the oil breather from the engine to return the oil to the tank. The Norton Atlas engine has a breather on the end of the camshaft or an L shaped breather pipe, and if and when the motor wet sumps a huge amount of oil is then deposited out of the breather. The breather is then connected to the oil tank, and the top of the oil tank has a froth tower and this can have the oil pipe directed to either the rear chain or out to the rear mudguard or to inside the rear number plate to exhaust the oil fumes and of course to send out some oil if the oil tank has been over filled at some time in the filling up process.

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Re: Oil tank

Postby John Donne » Mon May 09, 2016 5:30 pm

Your G15CS has the later oil tank when the Atlas engine was modified to take the oil for the rockers from the timing cover. The earlier oil tank has a built in restrictor so that the oil for the rockers is forced out of the short pipe from the return feed and up to the top of the cylinder head via a short piece of oil pipe, and then to some metal tubing that is bolted to the two holes in the cylinder head to feed the inlet and exhaust rocker arms, and spindles.

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Re: Oil tank

Postby Peter Morris » Mon May 09, 2016 8:31 pm

Yes Anthony, before I had a spigot for the breather pipe brazed onto my tank the breather pipe used to hang down by the centre stand. Every time I started the bike after a lay off (sometimes only a couple of hours) I used to get a 4" patch of oil on the garage floor...... AND it has an anti wet sumping valve fitted. Obviously not a very good one :?

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Re: Oil tank

Postby John Donne » Tue May 10, 2016 9:38 am

Even when the breather pipe returns oil to the oil tank the oil tank breather pipe can still vent oil out of the oil tank breather pipe. You have to be carful not to over fill the oil tank as his can also cause a problem. AMC did not make it easy for owners when the have to fill up the oil tank as the oil filler orifice can and is very restrictive to either fill or even view the oil level. When you leave the bike standing leave the engine on compression as this restricts the oil draining via the oil pump, through the con-rods and into the sump. The oil pump may also need looking at as the brass plate may need to be flattened using some plate glass and emery paper. Norvil do a conversion that adds a non return valve in the timing cover, and this is meant to stop the flow of oil past the oil pump. It was introduced on the Mark 3 Commando models

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Re: Oil tank

Postby Reynard24 » Tue May 10, 2016 6:31 pm

I'll have to check my bike with the dating officer as the V5 states it to be manufactured in 1965 and yet it has the timing cover feed to the rockers, simple flat brackets on the oil tank and yet it does have the engine breather spigot on the back and froth tower. It is also described as a G15Mk11 but the engine has a number with CS in it (frame and engine numbers match). It also has the larger touring tank and large bore exhaust pipes - I've not seen these on any other G15 - the others I've seen have the narrower pipes with flared ends at the cylinder head.
Filling these oil tanks is really a bind - I use a small funnel with a length of 1/2" diameter hose attached which just squeezes by the return column in the tank. I find an LED torch comes in handy too to check the level.

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Re: Oil tank

Postby JEAN-NOEL » Tue Jun 21, 2016 7:24 pm

Hi Peter,
I was this afternoon at the National Motorcycle Museum :both G15, 1964 et CSR 1965 exposed have the same tank as that presented on the picture.
J.N.

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