Excessive oil in sump?

Previously Jim Brierley wrote:

The 300ml doesn't seem excessive if the engine's been stood a while after shutting off, as there will be some oil draining from the timing chest down to the bottom of the flanged washer adjacent to the crankcase main bearing. Try checking the amount of sump oil straight after shut down of the engine, you will probably find it's a lot less than 300ml.

As for the oil burning, do you have 3 piece oil control rings and inlet valve guides seals fitted?

Jim

I measured the quantity of oil in the sump shortly after shutting down.

The oil control ring is of traditional design and is not a muli-piece item. (I won't use the 3-piece rings anyway after installing a set in my Commando. They made a right mess of the bores such that when I came to get them re-bored it was necessary to go up by two oversizes)!

I fitted new valve guides but they did not have the necessary undercuts to fit seals.

Previously Gordon Johnston wrote:

Is the bike burning oil on startup or during general riding? If it's during general riding, it is most likely the bores - possibly a new set of rings would sort that. If it's just on start (they all do that Sir) it's most likely the traditional Norton wet sumping. If mine has been sitting for a month or so, it does emit a cloud of smoke on starting but it quickly clears. This can disguise the smoke from worn valve guides. If it's guides, you would expect to see some exhaust smoke on every start. Of course, the grade of oil you use makes a big difference to wet sumping. If you run 10W-30, oil will seep through the oil pump faster than if you useSAE 50. Really, if you get a big cloud of exhaust smoke on start and your bike has been standing less than a week, I would take a close look at the oil pump.

Gordon. The engine smokes both on start-up and during running. It is not a wet-sumping issue because (a) I have been using the bike regularly and (b) I fitted an 'anti wet sump' valve because I concluded the accumulation of oil in the sump to be excessive. I do think that approx 300 ml - more than 1/2 pint - seems excessive; most of my other bikes do not accumulate that amount.

I wondered about the pump but this seems to be in reasonable condition, with no sign of excessive play, and the delivery to the tank is fairly 'brisk'. I have a spare pump so I might substitutethe existing with this as an experiment.

The guides are new but without oil seals.

The rings are new (as supplied with the pistons) but I don't know their origin - the pistons have no manufacture's markings! Piston-to-bore clearance is 0.006" (the subject of another discussion) which seems a bit more than I would expect. Ring gaps are around max spec. However I wouldn't have thought these factors would be the cause of the effect.

I wondered whether there might be an excessive delivery to the top-end (grasping at straws)!The rocker gear is fed from the delivery side of the pump with a banjo fitting directly off the timing cover (as with the Commando) and the more traditional feed, from a bleed-off banjo on the return tube, is in place but blanked off. Not sure why this was done.

I may obtain another set of rings but I still feel the quantity of oil accumulating in the sump is the cause. The 'return' side of the pump has a greater pumping capacity than the 'feed' so why am I draining off more than 1/2 pint?

Previously ian_cordes wrote:

As the oil feed is from the pump, you must have a 6-start set-up on your pump. This will deliver a lot of oil to the top end, so your valves, guides and seals need to be in good order. You must have 3 piece oil control rings with this system. It may be that the experience you had with the Commando was because the ends of the middle control ring overlapped, scoring the bore.

Also, you said there is no excessive play in your pump; there must be absolutely none. Have you had the pump apart? There may be chipped, or scored, teeth, which will cause wet sumping, and could affect the efficiency of the scavange. Have you checked the rate of return to the tank visually?

Ian. There is no discernable play in the pump but, as yet I have not dismantled it for inspection because the return flow to the tank looks as good as expected.

Regarding the delivery to the top-end; I am thinking that I might experiment by re-connecting the original bleed from the return tube rather than using the feed from the back of the timing cover.

Previously robert_tuck wrote:

As you have a bit of a miss match in parts ,Its just possible that you have an early engine that has been fitted with a six start pump gear set and pressure rocker feed . In Which case you could revert to the orriginal pump gear set up with the existing one piece oil ring and change to low pressure rocker feed, If you have the cylinders off, look to see if the rods are drilled for piston lubrication or not. You will also need to check if you have scrolled or plain rocker spindles. The Deciding factor will be if the rods ARE drilled as that will have to have the higher rate oil pump set up. Its also likely that the rings have not bedded in yet making the problem worse.Properly fitted 3 piece rings should not damage the bore. A further Thought!. even if the rods are drilled they can have been fitted with plain undrilled shells,you would have to pump some oil up the crank to see. At this rate you will be an expert in no time!.

Robert. Although the engine had been rebuilt before I acquired it, I dismantled it to change a poor camshaft (one lobe was way out of spec). Anyway, as far as I recall, the rods are drilled to lubricate the bores and the B/E shells drilled to match. I can't remember whether the rocker spindles are scrolled but I suspect not.

The previous owner was a boy-racer, I think, because certain key fittings have been drilled for wire-locking, and a competition mag fitted etc. However I discovered, when I stripped the engine,that his technical standards were pretty poor!