51 G9 oiling modification/upgrade?

[chasdev]

I'm thinking of increasing top end oiling by installing a later version feed-side oil pump rotor set and 4 (up from 3)later style oil restrictors in the heads, while at the same time slightly enlarging the feed hole in the early type cam driven oil distributor.
I've snagged a new set of later version rockers and have even pondered opening up the top side oil bleed hole in these to better wet the ends of the rockers as well...
Any thoughts?

[Eric]

There were many many changes to the oiling system of the twins over the years. These of course were done by the engineers involved in the design of the engine and based the results of the field trial information fed back from all of the customers problems encountered at the time.

Many of the changes were later reversed or removed completely either the following model year or several years later. So as even AMC were not sure what should or should not be done I doubt that we are more able to advise you but some may have suggestions.

[Groily]

Can of worms really Chas. But if you upgrade to the fat feed pump you'll need the bigger scavenge to go with or you'll risk filling the cases faster than they can be emptied. That'll need the late deep timing cover then. Have to say that for myself I have never much messed with the original bits on the oiling side of my '54 500 and it's never had a problem. Metering jets on all 4 holes (ones with holes in rather than flats though I doubt it matters), early rockers, but I do use the later oil distributor with the flat on it because that was what was available when I wanted to replace that bit. The correct felt filter and associated bits. Quarter of a million miles tell me it's a broadly OK mix, half of them with me on it.
There are many tales of over-oiling as well, so there can be too much of a good thing!

[chasdev]

My view on the risk of over-oiling is that if all the plain bearings and bushes are fit correctly and the return side of the pump is healthy, the return should outpace the feed as the amount of oil past the bearings is restricted while the return is wide open.
Other than opening up the orifice in the rotating oil distributor a touch to increase flow to the top, it's really just an upgrade to the 56 arrangement, more or less.
If I could afford it, I would send the cams, followers and rockers out for special coatings, but at $40 US minimum per piece, more (and thinner synthetic) oil is my plan at least for now.Edited by - chasdev on 15 Jan 2011 9:30:21 PM

[wilko]

I have decided the later double capacity pumps don't really increase the oil pressure, because the pressure release valve still cuts in around 65psi anyway, but they certainly increase the flow for better cooling.

[Groily]

I was thinking more of over-oiling up top Chas than of scavenge trouble per se.
But I think the scavenge pump, however healthy, does need to be of an appreciably bigger capacity than the feed; the later feed pump gives a very healthy flow and a lot will build up in the cases quite fast. I (along with a few others and thanks to Don Madden for the idea), use an early scavenge pump as a feed pump on one 500 engine (not the unmessed with '54 I mentioned) with a late feed pump as the scavenge. The said large feed is bigger than the said small scavenge and so the combination scavenges well. It also fits under a Matchless timing cover, not sure about the AJS shape. The large scavenge pump will not go under either early cover by a country mile. Been there and tried that!

[chasdev]

That's the first I've heard of too much oil to the top, everything I've seen leads me to think the tops were under-oiled from day one..and changes such as larger feed pumps plus improved and additional oil passages in the rockers do little to change my mind.
I have three twins engines apart on my bench/s at the same time.
The 51, which has very nice standard size crank journals and bearings, along with the two from 56, all have badly worn cams, followers, push rod ends and (both ends of the) rockers.
Some of this wear was no doubt caused by neglect and abuse combined with crappy oil, but for all three to have the same parts worn down to nubbins, with (in the case of the 51) some other parts in very good conditon, has me movitated to move more oil up top.
I suppose the real reason I'm obsessed with oiling is the cost of new cams, followers, rockers and pushrods along with difficulty locating them that's got me worried.
No way this level of wear can be allowed to happen again under my watch (OR wallet).Edited by - chasdev on 16 Jan 2011 11:38:56 AM

[Eric]

I think all the cams, followers, and the bottom end of the push rods rely upon splash lubrication from within the crankcase, but I need to check the memory is not as good as it used to be.

The larger pumps were fitted mainly in response to a perception from the buying public that crank failures were due to inadequate lubrication, this was not really the case and many new problems were introduced by the larger pumps.

The biggest improvement that you can make in the oiling department is added good filtration, either in the return pipe its easy to do or preferably after the pump but before the engine but that's a bit more complicated.

[Groily]

I think you might have said they'd been thrashed to within an inch of their lives though Chas! I really don't think in normal use with regularly-changed decent oil the 500s will give any great trouble in those departments once you've got them set up right. Extra filtration could only be good, natch, but honestly I reckon you only have to do the job once and right and you'll be set for loadsa(s)miles as long as the parts are all of a match for the engines they're in. My '54 is on its original rockers, has had later cams (the inlet only recently), has had a set of pushrods because they got chafed at the head joint owing to poor gasket fit, but it's still on the followers it came with a lot of miles ago. I used it as daily transport in London for years, it's been round the Isel of Man a load of times, it's rolled along the roads of the American mid-West, and now spe

[Groily]

(dunno what happened there, that's PCs for you)

. . aks French. I reckon you will be able to relax once you've got it up together how you want it, because they're really good bikes in my biased opinion.