Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Improve oil to rocker boxes Triumph pre unit twins

This might be interesting to people, who like me, are worried about the very little oil getting to the rocker boxes.(One of my bikes is an Aermacchi Ala Azzurra and she gets plenty of oil to the rockers by forced feed directly from the oil pump).On my Tiger-100, 1955, after noting that the new valve adjusters showed signs of wair pretty quickly I put a hose clamp around the tube in the oil tank to restrict the small hole at the top.Effectively there was some improvement but measurements showed that to get a reasonable pressure of some 3 meter oil column (about 0.24 barg)half of the hole had to be covered. At low revs the pressure however still remained at about 1.5 meter of oil column (about 0.12 barg).If the hole is restricted further you risk that the hoses are blown off at high revs.Recently it came to my mind that a suitable spring loaded non return valve might be the solution.The non return valve is mounted in the oil return line to the oil tank and upstream of the valve there is a T-piece where on the branch of the T the oil line to the rocker boxes is installed.The original branch off to the rocker boxes at the oil tank I have capped off.I have set the spring to open at 0.7 barg (10 psig)and checked with a suitable pressure gauge (the oil column method is not practical anymore at these pressures, unless you put a clear petrol type hose about 10 meters up in the air). At high revs the pressure slowly goes up to some 1 barg,since the capacity of the non return valve is taken large enough (some 20 liters/minute at 2.5 bar pressure drop). Another advantage of the non return line is that the oil line to the rockers remains completely filled even after time, so there is oil up there after the first kick. So there is always oil with a pressure in the range of 0.7-1 barg going to the rockers regardless the revs.The non return valve is a 1/4 inch from Flowfit (www.flowfitonline.com)and costs about GBP 4.2 excl. transport outside the UK.For the fittings (hose joiners, T-piece, clamps etc.) I used stuff from advanced fluid solutions (www.advancedfluidsolutions.com.uk The whole system works very well, if you remove the screwed rocker box caps it is all greasy proving that there is really oil around there. (This also gives some peace of mind when riding through the country side).

While I know next to nothing about the pre-unit rockerboxes or oil flow, I can tell you that on the unit engines, very little oil is needed, but the oil needs to be deposited in very specific locations: valve tips and rocker arm ball pins.

In many cases, unless some sort of valve seal is used, increasing oil pressure or flow to the rockerboxes can have unintended consequences.

Steve

How many miles have you done with this setup?

The standard method of directing oil to the head (restriction of scavenge flow into the tank by hole size) is crude of course, but has no moving parts and cannot stick.

What happens when the engine is idling slowly and there is not enough pressure to open your valve? Does all the scavenged oil go to the rocker gear? That wouldn't be good!

New adjusters and valve tops show wear almost immediately. I don't think any amount of oil will change that.

I am not an expert on unit construction, but I believe these have internal oil canals in the rockers bringing the oil directly to the valve tips and push rods and there are I think longitudinal grooves on the spindle for some models.
Nothing of all this is on the early pre-units. The spindle has an internal oil canal and a circumferential groove. Oil is supposed to seep from between the spindle and the rocker at both ends of the rockers. This oil is moved around by the motion of the rockers and should find its way to valve tips, push rods and valve stems.
The quantity logically depends on the feed pressure and the play between spindle and rocker.
I have been watching the spark plugs and silencers frequently, and there is no sign of increased oil consumption.

I did some 1500 km so far.
I don't see the problem of valve sticking when the oil system is propperly maintained. The valve has hardened and ground internal steel parts (no rubber seats etc). The construction (with a guided cone) is comparable or even better than most pressure relief (ball) valves in early pre units. I forgot to mention that I have already longtime an oil filter (Norton Type) installed under the right swing arm directly behind the (separate) gear box.
The valve will always open, also at idling speed since the positive displacement (piston type) scavenge pump can bring pressure easily up to 4 barg or higher.The amount of oil to the rockers depend on the clearance between spindle and rocker and of course the pressure.
I took 0.7-1 barg because this approximately doubles the amount of oil to the rockers (at least theoretically by hydraulics law).
I stoned away the initial marks on the valve clearance adjusters.
Then I did a Moto Giro and Milano-Taranto under tough conditions and some local trips alltogether some 4000Km.When checking some pitting was observed and this did me come to the idea of increased constant pressure.Now I have stoned away the (little) pits and I will closely observe what will happen now on the long term.

I didn't know they ever used ball valves for oil pressure relief.

I mean the spring loaded spherical thing.
By the way this type of oil pressure release valve is on my BSA A10 and B33. The Triumph T100 has a sort of spring loaded piston for this purpose.

Triumph T100, 1955----Bonneville T100,2008
BSA A10, 1954---------Kawasaki W800,2012
BSA B33, 1956
Aermacchi Ala Azzurra 1963
Gilera Giubileo 1962

Lube to the rocker boxes does seem very borderline.

God knows how the valve guides get any lube at all.

The lower external oin drain bango bolts on the push rod tubes leak slightly on mine so there is definitely oil draining from the rocker boxes into the crankcase.

I always squeeze the return pipe behind the scavange feed for a few seconds on start-up. This forces some oil up the scavange pipe and into rocker shafts.

It's ironic that very little oil appears to go up there, but masses of it leaks out!

I also used to squeeze manually the hole in the return pipe when starting.
Now the sqeezing is done automatically by the non return valve,the pressure is controlled and it works permanently.
The BSA B33 for instance initially had no oil feed to the rockers, the (hot) oil mist was supposed to travel up via the (rather big)push rod tunnel coming from the ditribution side. Needless to see this didn't work well at start with cold oil, hence the addition later on of a feed line from the scavenge (gear type) oil pump.

Never heard of it causing a problem to the owner. Have you?

I bent up a short length (50mm)of stranded clutch cable inner nad jamed that in the hole in the oil return tower inside the oil tank on my pre unit.
Seems to get enough oil to the rockers.
Also on startup I further restrict the return flow to forcce a bit extra to teh rocker boxes.
Only do this from dead cold if she hasn't been going for a week or so.

Cheers,
Trev

I hope there is absolutely no chance of cable strands ending up in the moving parts.




Meaning, I suppose, that the bike performs and behaves like a normal unmodified Triumph?



That's fine if you like to add extra steps to your starting "ritual." Cold start is probably the time when the rockers get most oil, as the scavenge picks up the slug of oil from the bottom of the crankcase and pumps oil, before it starts pumping air.

I prefer to use a piece of coat-hanger wire (single strand).It will only increase rocker oil-flow by 25%,and pressure by about 56%.I suppose the increased pressure on the return pump consumes a little horsepower.

I don't do this because the spindles need more oil.They get about a teaspoon each per minute,which is plenty,and they never wear out.I do it to get a little more cooling oil to the head.1/2 teaspoon extra oil per minute is a drop in the ocean;I know.

Unless you've just washed all the oil off the spindles,they'd normally have enough oil on them for 5 minutes running with no further oil.

As long as you're not using valve-stem seals,the guides will get enough oil.I'd put most of the wear and tear on guides,stems and adjusters down to the very short rocker arms causing arcing and side-thrust.Even worse on a unit 500 or Trident,where the arms are 1/4" shorter (7/8" from spindle centre to valve stem,compared to 1-1/8").

Sit further back, on bumpy roads.

Yes, you are right it was the C11, but a similar thing was the case for the BSA pre-unit twins, there an oil feed to the rockers was introduced in the late forties (of last century).

triton thrasher, I thought nads were left and right, not inner and outer...........

Go nad, go!

You put your left nad in (to the froth tower)
You put your left nad out.

Never in a hurry on start up as our pubs and licensing laws are sophisticated, dont have to rush to beat the dinner time last bell.

Bollocks to you.....putt putt putt putt.

Todle pip all.

This is all true, the real issue on the pre units is the amount of oil coming from the spindles to lubricate the valve clearance adjusters/valve tips and push rod upper parts. I am convinced this is marginal in the standard design and it is clear that a bit more pressure brings some more oil to these places with an excpected reduction of wear and tear.(to be proven after some more km's)

Triumph experimented with pressure fed top end oiling via the plug on the timing cover. I think it was with the Thruxton. With a little innovation you could even meter it. I've considered it myself, but with the short life of the Triumph top end otherwise, it didn't seem to make enough sense to spend all that time.
Bill

Sounds interesting, do you know why it was not pursued?
I believe the plug on the timing cover directly communicates with the pump discharge.
You would also in that case need some form of pressure release/regulation as the plunger pump can reach (too) high pressure at the discharge side.
This is why I adjusted the pressure to the rocker spindles in the system I use at 0.7-1 bar(g)for the time being. I can easily increase or lower this pressure by changing the spring in the (non-return) check valve

The spindle oil feed system of a pre-unit was exactly the same on unit construction up until around 1968-69 when they decided to stop drilling the oil way in the rocker arm itself. The drainage system is different on iron heads, but the feed was the exact same.

The reason the valve train wears so much is:
a) The poor design of the rocker arm geometry
b) Poor quality oils developed for water-cooled automobiles being used in much hotter air-cooled engines
c) No real oil filtration system

The small amount of oil present is more than enough to do the job. Oil is drawn by forces of nature into small clearances and heated areas. This force is called 'capillary action'. So all the oil system has to do is place the oil near the needed spot and the forces of nature do the rest. The oil leaks at the top end prove my point.

Consider that it wasn't until the late 1930's that oil was even pumped to the rocker arms, and it wasn't until the 1940's that engineers decided to capture that oil and return it to the engine.

Pumping more oil to the rockers is simply going to create more problems.... like how do you intend to drain the excess oil from the push rod tubes?

:bigt


PS. Attached below is a photo of a Norton Inter. You can plainly see the exposed hair-pin valve springs and valve gear. Please explain how these manage to last even though they violate every point of your theory.

Pressure feed was tried on some very early Speed Twins, then dropped. I don't know why it was tried, or dropped!

Probably because all it did was rob the crank of oil pressure. Again, creating new problems where none previously existed.

Same thing happened when they tapped into the pressure line for the ex tappet oiler.