Oil passages

[RodneyK]

In rebuilding my G9, after my disastrous engine failure, I have paid particular attention to oil galleries and channels. So far I have traced the route from the oil pump through to the “rocker box oil feed gallery” in the cylinder sleeve, and up through the cylinder to the head. Here the passage up to the rocker arm appears to be blocked by some sort of brass plug. I cannot find a way around it with a thin wire. All four passages appear to be blocked. Please explain why this is, and how oil gets to the rocker arms.

Secondly, my manual calls the lower chamber in the cylinder sleeve the “camshaft oil feed gallery”. I see no ports for oil either in or out of this gallery. So how do the camshafts get oil? Running down from the pushrods perhaps?

Your help is critical in getting this engine running properly. Thanks so much.

[RodneyK]

Photo to go with above.

[dave16mct]

The brass 'plugs' are oil restrictors to prevent too much oil getting to the rockers. Some have holes in the middle and some have a flat machined on the edge. The holes are very small. I've just been working on my G11 heads and found 2 blocked. I used a fine steel guitar string to unblock them. It took me quite a while to get them clear. That wire you're using is way too thick, the holes are less than 1mm.
Yes the cams are lubricated with oil running down the pushrod tunnels. The galleries referred to are the 2 alloy tubes which press into the crankcase to help to oil the cams on start-up from cold.
Dave.

[RodneyK]

That is so helpful Dave. I’ll be sure to get those tiny holes clear before proceeding.
It’s quite likely I’ll need more of your help as I reassemble my engine. Much appreciated.

[dave16mct]

You're welcome. What year is your G9? They did change the oiling system around a lot!
Dave

[Duncan]

There is a picture of the hole type on the AMOC Parts list:
https://www.amoc-parts.com//store/comer ... duct=21349

[1608]

According to the manual these restrictors were deleted ( I believe in 1959 ) but re-introduced in 1962 probably because of over oiling issues.

[RodneyK]

Mine is a 1955. I have a pair of spare heads which do not have the restrictors. That’s what confused me. I’m getting to know this engine, but still lots to learn.

[Groily]

I have always run my twin engines, 2 x 500 (1953 and 4) and 1 x 650 (1961), with restrictors on all four corners. I've used the ones with holes and the ones with flats, without problems. I've never in 48 years of 500cc-ing had any issues with oil delivery to the top end via the distributor bush (both types), galleries and restrictors, nor with rocker shaft or camshaft lubrication. Nor with piston or roller main bearing oiling come to that.

The critical things are that the crank is clean as a whistle inside, with the centre web sitting properly and not binding, and that the feed-side oil pump and filter chamber, with functional pressure relief valve of whichever sort, are all present and correct and in the right combination for the particular motor. We are even blessed now by the availability of new thrust washers for the centre main, thanks to the Club.

The anti-drain ball valve (captive or detachable depending on model/year) in the end cap for the crankcase oil filter should be in decent shape to give the top end loop a bit of a head start, but for the wellbeing of the crank and rods (which is where Fate dealt you its unwelcome hand) it's the main feed to centre main & b/ends and the state of the three journals and shells that matters most.

There will be good news to come though. The late great Alan Jacobs (aka 'Biscuit' ) said somewhere on here that he expected 60,000 miles between bottom end rebuilds on his twins. Not sure I can claim that, but one is now well towards 40,000 miles since last being attended to, and going strong in close to daily use. So there's much to look forward to when you've got this thing sorted!

[RodneyK]

The crank is on its way home from a machine shop halfway across the country. It’s been spray welded and ground back down to specs. This time I will thoroughly clean every nook and cranny of everything, especially after seeing all the metal filings and flakes in my oil. I had the case welded, rather than use a spare, (to preserve my serial number for the paperwork) and should be re-assembling soon. Thanks so much for your encouragement.