1947 exhaust valve oil drilling

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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1947 exhaust valve oil drilling

Postby hatrack » Wed Sep 13, 2017 10:06 am

My '47 iron head, coil valve spring, has an oil feed adjustment screw to the inlet valve guide.
but there is another similar drilling to the exhaust valve guide. This has no adjustment screw in it. Should there be one?
I have looked in Niell and in Haycraft, but neither show any useful view or mention it.
I have run the bike but there are oil leaks, principally from the push rod tubes (They even felt loose. One top seal had one metal washer, the other had none) but there are leaks from above there, probabaly from the rocker cover, but maybe from this uncovered drilling?
Mechanically, all looks good, but I am removing head and barrel to put back the black paint that was there befor the rust took over.

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Re: 1947 exhaust valve oil drilling

Postby Rob Harknett » Wed Sep 13, 2017 11:40 am

Ashampoo_Snap_2017.09.13_12h27m00s_001_.png

You should see in the oil circulation diagram, both valves are lubricated the same, with the exception, the inlet has an adjustment screw to limit the oil supply. I believe the screw fully tightened, then open 1/6th of a turn. All should be seen and read in your bikes instruction book.

http://archives.jampot.dk/book/Owners_m ... Manual.pdf
I would also use this WD manual in conjunction with 47 500 books for general info. 98 pages of info on the single only, which is not so different from your 47 500.
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Re: 1947 exhaust valve oil drilling

Postby hatrack » Wed Sep 13, 2017 12:22 pm

Thanks Roy very helpful to have that link to the 350 manual.
However, that diagram does not shoe the actual drilling in the head.
Mine has no thread in it so can take no blanking screw, yet without being pugged in some way it appears to be bound to leak oil rather than feed it to the ex. valve guide.

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Re: 1947 exhaust valve oil drilling

Postby zwarts » Wed Sep 13, 2017 12:53 pm

The exhaust valve guide oil feed is not regulated. Oil collects in the small well, passes through drillings in the head which mate up with the hole drilled in the side of the ex valve guide, wets the valve stem and then drains through another drilling which exits just above the ex pushrod tube seating in the head. A very simple and effective system, don't blank it off! Your oil leaks are almost certainly due to the incorrect assembly of the steel washers and sealing rubbers. The top seals are best replaced with 3 or 4 O rings, size BS210. The bottom seals can also be upgraded to BS 304 O rings. None of this will have any effect if you fail to have the correct steel washers at the top. When all is assembled, the pushrod tubes should be tight in the head and at the base.

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Re: 1947 exhaust valve oil drilling

Postby hatrack » Wed Sep 13, 2017 2:12 pm

Thanks. Great suggestion about the "O" rings.
I still don't get it with the oil drilling. It runs horizontally from outside surface of the head, level with the inlet oil control, about 3/4" from it, straight to the exhaust valve guide.
But the other end is open to the atmosphere.
There is a drilling into it from above, obviously feeding oil to the exhaust valve guide, as you say, unregulated.
But what stops that oil running out through the opposite, open end of the horizontal drilling?

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Re: 1947 exhaust valve oil drilling

Postby hatrack » Wed Sep 13, 2017 2:39 pm

I found the 210 rings, but cannot find BS304 listed anywhere.

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Re: 1947 exhaust valve oil drilling

Postby Rob Harknett » Wed Sep 13, 2017 3:44 pm

The oil basically just drips down lubricating parts on its way to the sump, The inlet valve is regulated to the min. required. Too much will result in oil getting sucked in with the mixture, perhaps foul plug also could cause more burning of oil and smoke. The only thing you really need to watch out for is, you don't block any of these drain holes. Perhaps with gasket sealant on the rocker box gasket.

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Re: 1947 exhaust valve oil drilling

Postby zwarts » Wed Sep 13, 2017 4:02 pm

'But the other end is open to atmosphere'.
Unless your head has been modified, this drain exits into the ex. pushrod tube tunnel just above the pushrod tube and its assembled seals. The oil then drains down the pushrod tubes, lubricating the tappets and guides as it passes into the timing chest.
I will check on the BS304 O rings, I may have the no. wrong!

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Re: 1947 exhaust valve oil drilling

Postby hatrack » Wed Sep 13, 2017 4:13 pm

I understand that the iron head is different to the ally head in this area.
The hole is obviously original as it has to be drilled from the outside.
It seems to me that it should be plugged at the outer end, but there is no internal thread and no other sign of it being so in the past.
Removing the rockerbox, I noticed that the hole in the gasket for oil to run into this oilway was pretty completely blocked with silicon gasket goo, which could explain why there wasn't a constant trickle of oil on the outside, and maybe why the previous owner said he had trouble with the exhaust valve seizing, not altogether surprising if it wasgetting no oil.

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Re: 1947 exhaust valve oil drilling

Postby zwarts » Wed Sep 13, 2017 4:53 pm

Yes, I am very familiar with the iron heads. It does sound to me as if someone has modified your head, any chance of a photo showing the offending region of the head?

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