Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Oil pumps: 4-valve vs. 2-valve?

Having received an '82 Triumph parts book, I noticed the 4-valve oil pump, standard on the last 750 Triumphs.

The two-valve pumps served Triumphs well for racing as well as for everyday road riders, so I ask:
what advantage does the 4-valve pump have over the old 2-valve pump?

Hi Irish Swede, It is said 4 valve was able to more reliably pump dirty oil that may has sludge in it.
I don’t know if that is true or not.

Friend fitting 4 valve to try to increase hot oil pressure at idle. Before & after tests installing pump in ‘76 T140 motor, it made no difference whatsoever in pressure meaning volume is the same as old pump.

Oval port pumps have a slightly higher volume than round port.

I changed ‘73 Tiger original oval port to Morgo pump. Visibly the return volume looks less. Initial observation shows lower oil pressure at idle. However true idle pressure tests must wait until break in oil is changed to normal oil.
10-15# lower. We’ll see though.
Don

The second ball valve on the outlet side of the pump (so two in series on the feed and two on the scavenge as there's no one-way valve on the intake side of the pump, oil is drawn in by vacuum that relies on the outlet one-way valve closing) increases the reliability if one ball is held off its seat by dirt then the pump will continue to operate normally due to the second valve.

The standard two valve pump was generally so effective and simple, but the 'grit under the ball valve' issue has always come up time and time again. Therefore, the back up valve argument would seem to hold water (or oil).

If fitting a f our valve pump you need to relieve a little bit of a casting web around the pump.
It’s not difficult, just don’t go too far

Basically if you are confident enough to change a pump, the Dremel work is easy

"Oval port pumps have a slightly higher volume than round port." Could you explain this? Is the bore or stroke different on the four valve? If it has higher volume I would expect a high pressure.

Hi Dave, The bottom of the oval port is higher. Plus the wider port with flat bottom gives a bit more volume.

Of course piston stroke is the same. But the “cutoff”, the point that piston fully covers the feed port is higher. So the “effective” stroke is greater volume of oil.

I did a thread on RAT with photos & figures. I’ll link it later from my PC.

On paper the volume calculated a fair amount more. At the time I didn’t know if “real life”. Would actually see a difference. It does visually to my eyes. Hot oil pressure test is the real test. I did oil pressure test on original pump before arm down. I videoed tests.

I chose Morgo due to the high quality. Indeed Morgo quality was up to the high standards I’d hoped for. The oversized pistons do give more volume than standard round port later pump.

I hate to say it but Harris products sometimes lack quality. Emgo maybe worse? Are they made in same factory?

My dream would be Morgo oval port pump.

I’ll try to send link later today, but may be after Christmas.
Don

Don is 100% correct about this, I was skeptical at first, I then did some rough measurements comparing a new Morgo pump to an original oval port, and the calculated volume on the feed side, from memory I hasten to add, was something like 3.85cc/stroke for the Morgo and around 4.15cc/stroke for the oval port!

To say I'm disappointed that the upgraded Morgo has less pumping capacity than the original pump would be an understatement. The oval entry ports are an important feature on the later Triumph pumps that for some reason Morgo have failed to incorporate with their "improved" version. I agree with Don that the quality of the Morgo pump is excellent, it's just a shame that the slightly increased diameter of the plungers on the Morgo is nowhere near enough to make up for the lost volume from using a simple drilled round port compared to the oval port.

Hi Dave, Here's a link to RAT group with photos. You can see very plainly the huge difference in cutoff point.

https://www.triumphrat.net/threads/...t-twin-oil-pumps.984180/#post-2004208345

Also the gasket might make a difference. The early T140 type parts book shows incorrect pump gasket part #. They actually came with the latest gasket version shown in later T140 parts book.
Don

Hi All, Not even all oil pump gaskets of correct part # are made the same...
Here is my motor. Go to page 13 about half way down.

https://www.triumphrat.net/threads/tr7rvmans-motor-overhaul.979391/page-13
Don

Providing the motor is in reasonable condition wouldn’t max hot oil pressure be determined by the pressure relief valve and not the quantity of oil pumped?

To TR7RVMan:

Don, looking at your column on TRIUMPH RAT, I have a question:

Where do you find 7.4 to 1 pistons? I am rebuilding a '70 TR6R for road use, and the maximum compression ration I want is 8:1,
which is about what the old T110 models had, High speed is not a consideration, but torque, reliability, and fuel availability, are.

I am considering a 750 kit for this bike. Are 7.5 - to-1, or 8-to-1 pistons available for a 750 kit?

Hi Bloodknot, Yes max pressure is determined by the relief valve.

Low rpm pressure is determined by volume. Especially at idle. The same motor, same oil, same temperature…. More volume results in higher pressure.

Does the higher pressure matter? That is another subject.
Don

Hi TR7RVMan; regarding Morgo quality. I have both models. I say that the design of the plunger one have a flaw where the nuts are; I mean; is not possible to use a socket and with a wrench you need to work from a side doing 1/5 of the whole turn.

Hi Irish Swede, my personal experience is 7.1 650 pistons makes the sweetest running bike. Bonneville shop sells them. They will give you about 145# hot compression. Only have used these with points. Electronic ignition has a slower advance curve which you may notice or not. Properly serviced points is the most reliable as they allow starting with a low or dead battery. Poorly serviced points are the worst.

MAP cycles sells a 7,5 billet piston. A few places may have some old 6T pistons.

My friend has Morgo 750 kit on ‘70 Tiger. Older Boyer ignition. Has proven durable long term. I don’t know the compression ratio.

T140 pistons cannot be used with big bore kits for 650. Wrist pin is larger & wrist pin hole in different location. Bonneville shop sells T140 7.4 pistons.

Personally if you want a really easy starting & riding bike 7.1 is what I would put in my 650. Make no mistake, the bike will go up the hills & run 70 mph effortlessly on the highway. They just do.
Don

Don, at my age, add to that a five-speed gearbox, and the type of performance you describe is all I would ask for,

I've always thought that about the attachment nuts for the oil pump and how shallow the hex is. I've noticed similar inaccessibility with nuts and bolts of other 1940s/50s machinery and think it's because most users would have used thin wall box spanners in those days. The military used sockets (I've got at least one of my dad's old WD sockets stamped 1945), but your average bloke in the UK back then wouldn't have had them.

Hi All, If own a Triumuph you pretty much need a grinder. You’ll need to grind several tools for clearance. This is very common practice throughout the automotive world. You’ll need a full set of tools in both “Whitworth/BS, Imperial. Plus a bunch of special tools shown in shop manual. If you can make them you can save some &. Even the shop manual speaks of “self made” tools.
Part of the cost of Triumuph ownership if you do your own work. You are basically the “dealer mechanic”. So you need the tools the dealer had. Many USA dealers had gas & arc welding equipment as well as a 6” or larger lathe. Even the tiny dealer close to me had all that. My first visit there was in 1964 with uncle Louie. 2 weeks later my Dad bought our first tel motorcycle. Suzuki 50. They had a new Bonnie in the show room window. That view effected me deeply!
The work shop was tiny, but very complete. This proved typical of Triumph dealerships in the San Francisco area. Not rink a dink at all.
Don

I have lower compression pistons in my 67 TR6R. I'm not sure what the ratio is but they look lower than the original type. They are unusual because they are stamped "Made in Japan". The bike certainly doesn't vibrate much. If the points get dirty it does a bit. When all in order it runs very well. When it would start vibrating I originally thought that the timing was out so re strobed and at the same time cleaned points but it was just the latter that fixed it. I do keep it in tune as well.

7:1 pistons for the unit engine are easily available but are different to pre unit.

As to oil pumps I have the original and it seems fine although a 67 doesn't have a warning light and I have no pressure gauge. I think the last two are key to worry free riding!

Dave

I thought the twins made before they fitted an oil light all had an oil pressure indicator button on the pressure relief valve.

To get back to Irish Swede on the big bore front, in the UK there are two manufacturers of big bore kits, Morgo offer 9.5:1 and 10.5:1, while Aerco are 8.9:1, all to high for you. However, both would probably sell the big bore barrels separately, and the MAP cycle 7.5:1 pistons are specifically for these, with the correct pin height and diameter for a 650 engine. You would then be able to ride lie Don says, but surprise a few people if it took your fancy!
If you wanted help in sourcing the big bore barrels, I can probably help.

My '58 3TA had a tell tale on the relief valve but a 67 650 doesn't seem to.

My '65 TR6 hasn't either. I think the light came in about 1969.

I think you may be talking at cross purposes, the early 3TA would have the button tell-tale that was on the pre-unit engines, the 69 on pressure switch fitted in the oil gallery

I knew what I meant! Yes, the switch was in the timing cover that I recall could so easily break out if over tightened. On my '65 the PRV has the domed head, with no tell tale. I wonder why they deleted the tell tale - oil leaks, maybe?