twin oil circulation

[clive]

I am currently rebuilding my 58 G11CS after finding lots of problems caused by finding a mag pick-up brush behind the oil pump in the oil supply to the filter chamber. Apart from damage to the big end and centre main shells and to the main bearings there is evidence of shortage of oil by wear of one of the cam follower spindles.
I am now looking at the oil supply in general and am convinced I have seen a diagram somewhere showing the circulation system. Despite searching the archives and technical articles and forum I cannot find it. Anyone know where it is?

Alternatively can anyone confirm if the plug/restrictors I have found in the drive side crankcase should totally plug the supply hole or simply reduce the flow. The ones I am talking about are in the oil "tray" immediately below the cylinder base. Both crankcase halves have drilling to supply oil up to the rockers via drilling in the cylinders. This oil will eventually drain down the pushrod tubes to the cam followers. However both crankcases also have a drilling which breaks straight across into the pushrod tube immediately above the follower. These holes are plugged by what appears to be a split restrictor. However what appears to be a hole in the middle of these restrictors will not respond to cleaning with a fine screwdriver. So the question is are these actually plugs or restrictors. I don't want to open them up if they are plugs and are supposed to ensure the oil reaches the rockers. Cannot see why they would have been drilled through and then plugged though. help much appreciated

[CR]

Hi Clive, they are restrictors (or jets)...should be part number 018890, same as the jets fitted to the twin heads (well some of them). They have a fine hole drilled through the centre of a brass jet. Trouble is, when people drift them in they tend to overdo the job and flatten the face, which blocks the hole.

You could possibly also find these jets in your heads for 58. In 59 they dropped them from the heads and then re-instated them in 61.

I've got some in the shed - somewhere. If I can find one I'll measure the hole so that you can always just drill them. If not, Gary should have them in stock and so should be able to measure (with a drill) to find the bore size. NOTE: it's easier to drill them in situ rather then replace and then have to drill the new ones because the faces are peened over.

All the change history for thee twins is here: https://www.jampot.com/article_print.asp?id=20

[clive]

many thanks Chris that would be very helpful. And yes I did notice them in the head so will have to check if they are free too.

[CR]

Can't find them Clive. Check with Gary to see if he's got them in stock.

I seem to remember that on certain twins only three restrictors were fitted in the heads. They didn't fit one to the R/H exhaust as that was the furthest from the oil supply.

[1608]

I read somewhere that the dia of the holes in the restrictors is 1/32". The restrictors in the c/case oil gallery certainly should not be blocked! Whether or not there should be a total of 4 x restrictors in the heads or whether one was omitted I'm not sure as I've never seen it written anywhere. I have heard of one restrictor being left out but whether that was somebody's personal take on the matter or not who knows? What I would suggest is that;- If one restrictor was to be omitted then the oil would take the line of least resistance, take the route via the un-restricted oil-way and thus starve the other rockers.
Can anyone confirm whether the ONLY oil supply to the cam followers is that which comes from the rockers and down the push-rods. If so, then its no wonder they wear like they do.

[Groily]

Just looked at some brand new metering jets I have on the shelf.
It's one of those 'yes and no' things. There is a two-step hole - about a 32nd for the first (and longer/deeper) portion, but then the real restrictor bit, towards one end, is just 22/23 thou. Ie very small and hard to poke anything through. About a Number 70 drill would do I reckon (subject to more accurate findings from Gary). In fact as I recall that's what I used to make some, for which this new set is a replacement next time the heads are off my 500.
Never really thought about how the followers are oiled until now. I just assumed it rained on them from one end, and oil was sloshed around in their general direction from the camshaft troughs/rest of crankcase as well. If the cam lobes get wet, things should be OK I'd have thought? Haven't really had too much follower wear over the years on that one. I've replaced them twice and the pins once - and both camshafts once too - in 36+ years of pretty continuous use. I think their service life compares reasonably with the 'up and down' followers to be found on many other engines of the day, but as I always say, I've been fortunate with that bike, it's always treated me well.

[SPRIDDLER]

"Cuh! Twins eh? Who'd 'ave 'em?"

[Groily]

It's what my mate said Neville, when he got 2 daughters all at once.
(Misprint in my earlier one "a 32nd" should have said "about 3/32nd" for the fat end of the 'ole. Makes no odds cos that's not the important bit, but just for clarity . . .)
Cheers, Bill

[clive]

been working on the Hxxxa trail bike this morning will have a look this pm, if the hole is that small maybe they are not blocked!!

[clive]

Many thanks for the advice all of you. In the end I had a poke around in the wider section to get out all the muck that had accumulated there with a dentist's instrument (but a needle would have served the purpose) and then was able to clean the remaining muck out of the fine jet with a very thin piece of wire as there was by then no real resistance. Crankcase one now in the oven, bearing outer in the freezer, extractor fan on, Hilary at work