Big end oil feed

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Big end oil feed

Postby Greybeard » Fri Dec 18, 2020 3:36 pm

I'm pretty certain of what course of action I'm going to have to take but thought I'd run this past you before the 12 ton press comes out of its corner for an airing.
It seems that the 1955 16MS Green Lane project likes to throw up problems and snags every step of the way - serves me right for buying a non-runner I suppose.
I've managed to build a good gearbox from the one that came with it and a spare box from a Section mate (thanks, Mick) and also had the cracked oil pipe housing welded (a superb job too by Tony at AJ's in Hull). The latest slap in the nads has surfaced whilst I was cleaning up the crank ready for putting back in the cases with its new roller bearings.
It has obviously had a new big end fitted at some time in its life judging by the alignment marks scribed in the edges of the flywheels, and has been running with it fitted long enough for the nuts to have acquired a 'patina' suggesting some years of use.
What I can't get is an oil feed from the hole in the timing side axle to the big end (I've sealed off the drilling in the pump worm). I know the book clearly indicates that there should be a feed and that's backed up by this excellent thread
viewtopic.php?f=18&t=25068&hilit=big+end+oil+feed
My question is, were there any known big end replacements made that relied simply on a splash feed as per my Panther - or do I have to assume that the big end pin has been misaligned closing off the feed? One end of the pin has a drilling for the lathe centre whilst the other (timing side) is machined smooth, so may well have been plugged. Similarly I cant see any plugged drillings in the rims of the flywheels unless they've been drilled at an angle from within the pin/axle holes (the timing axle keyway is aligned with TDC so I'm happy with that part)
As I said, I'm pretty sure what drastic course I should take - I just want to rule out the possibility of a splash feed bearing - which as it happens feels pretty good and is certainly serviceable.

I never had any of this aggro with my 61 G80 :roll:

Steve (wot'll be really despondent if he finds has to stump up for a new big end)

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Re: Big end oil feed

Postby ajscomboman » Fri Dec 18, 2020 4:10 pm

I'm afraid you'll be digging out the press as the end relies on a feed and not splash. If it makes you feel any better I've just had to pull the bottom out of a G15 after 25 miles due to a piston nip up and a crank that wasn't quite shimmed as close as it could have been. Not forgetting a new rotor and stator etc. All sent to try.

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Re: Big end oil feed

Postby Rob Harknett » Fri Dec 18, 2020 4:50 pm


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Re: Big end oil feed

Postby Greybeard » Fri Dec 18, 2020 5:36 pm

That's really just as I thought, chaps. I'd been looking at that same diagram on page 16 of the manual and was pretty certain it would be the case, Rob H. I guess AMC must have drilled the oilways at an angle rather than through the full diameter of the flywheels after all - not even a sludge trap for access :roll:
It's a job that can wait for tomorrow now - perhaps a night on the Glenmorangie may refresh the flagging enthusiasm :|
I shall report back with a diagnosis.
At least I'm still at the stage where it can be sorted without a engine full strip down. I feel your pain, Rob S - and wear a similar T-shirt! (mine has a picture of Sunbeam gearbox on it that I got intimate with four times in a row before I finally cured the whining)

Steve (wot really shouldn't be dipping into his 'flat tanker' fund with yet another project)

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Re: Big end oil feed - an update

Postby Greybeard » Sun Dec 20, 2020 5:31 pm

Well, I've got a bit further and discovered a problem that may well keep all you singles owners awake tonight ;)
My attempts to loosen the crankpin nuts with my windy gun, then a mate's expensive electric impact wrench both failed dismally. This morning I borrowed a huge engineering vice that has lying around in a friend's garage for years. I eventually got it lifted onto and bolted to my bench so that I was able to clamp the flywheels in it. It took quite a bit of effort with a 3/4 drive socket set and a long bar to shift them before I could get to work with the press.
My initial thoughts as I removed the pin was that it hadn't been drilled for an oilway.
Oil hole 2 640.jpg

It was only when I started scratching around that I discovered them. No wonder nowt was getting through - they were blocked absolutely solid! I'm not talking about proddling with a pin solid, but having to drill the compacted stuff out type solid.
Oil hole 1 640.jpg

Oil hole 3 640.jpg

I also had to drill out the plug in the end of the big end pin to drill along the oil way to clear it completely.
Despite what has obviously been years of neglected oil changes that big end appears to have survived pretty well and is still fit to use. I'll give simply bearings a ring in the morning to see if they can get some new rollers to me before the non-christmas shut down so I have something to do that will save me having to watch some dismal TV.
It did get me wondering as to how many singles are thumping around with similarly blocked oilways. Clearly the big ends do get some lubrication from what's splashing around in the crankcases and it appears to be enough for them to keep running for thousands of miles. This blockage certainly isn't the sort of thing that has built up overnight.
It definitely highlights the need for regular oil changes I think to keep all those drillings open. Please refrain from mentioning the myths and legends regarding detergent/non-detergent oils though. It's been done to death many times and usually hinges on a misunderstanding of what a detergent oil actually does :roll:

Sleep well, folks.

Steve (wots hoping to have got away without a new big end being needed)
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