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Discussion Starter · #1 ·
This was on my '70 TR6R when I acquired it. It doesn't have the standard oil return pipe, which should end in an adjustable tee for the chain lube feed. Top of this tube is sealed and welded to the inside wall of the tank. Oil flow is controlled by a fixed hole about 3/32" diameter drilled in the side of the pipe near the top. It doesn't flow enough oil and the engine still wetsumps after about 30 miles, even after installing a Morgo pump and reaming the pipe out with a 3/16" rod.

Does this tank come from one of the 500s?



And -- if I open up that regulator hole will it reduce flow to the rockers?
 

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Hi -- for 1970 there was a new tank - i believe the same tank was used in 1970 for the 650 twins and the 500 twins ( more knowledgeable amongst us may correct me on that ) -- for 1970 the adjustable chain lube feed was completely deleted and no part of it was fitted -- the tank also had an increased oil capacity ( its a bit fatter) --- looking at my tank , which i believe is correct for a 1970 T120R - i cannot see the oil return pipe in the oil tank opening - in my tank the pipe ends near the tank openning but not visible - i can feel it with a finger and i can also feel the hole drilled for the oil to come out - so i dont know if your tank or my tank is correct !
--- not sure why you say its not flowing enough oil ? -- i would say the oil flow quantity is determined by the pump - and you say you have fitted a Morgo - obviously oil flow will increase as engine speed increases - the pump will "force" oil into the return pipe to the tank - part goes to the tank and part feeds the rockers - the hole in the pipe in the tank is a somewhat crude metering device to ensure some oil goes to the rockers and the rest into the tank - what i am try to say is that you will not affect the quantity of oil returning to the tank by adjusting the hole in the pipe inside the tank - increasing its size may be starving the rockers of oil ---- what are your symptoms of wet sumping ? -- these engines by design always have a small quantity of oil in the crankcase
 

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Hi,

This is confusing.

Does this tank come from one of the 500s?
'67 to '70, 650's, 500's and 350's used the same oil tank.

It doesn't have the standard oil return pipe, which should end in an adjustable tee for the chain lube feed.
Yes and no.

Chain oiler was deleted from US-market twins for '70 and from all 500's '71-on. Before this, the chain oiler outlet was a small spigot exiting rearwards from the oil tank filler neck, controlled by a special screw and friction spring visible and adjusted through the filler neck.

Top of this tube is sealed and welded to the inside wall of the tank.
The oil return within the tank is always "welded to the inside wall of the tank" and has a sealed top - or the returning oil would squirt out of the filler neck.

Oil flow is controlled by a fixed hole about 3/32" diameter drilled in the side of the pipe near the top.
:Huh Oil flow isn't "controlled" by anything, what would be a requirement to "control" the flow of oil returning to the tank from the engine?

if I open up that regulator hole will it reduce flow to the rockers?
The largest you can "open up" the hole (not "regulator") is the ID of the return pipe. On a '70 tank, the rocker feed spigot is off the main return to the tank just before it enters the tank

the engine still wetsumps after about 30 miles, even after installing a Morgo pump and reaming the pipe out with a 3/16" rod.
:eek: As there is nothing certainly in a standard unmolested tank that would affect oil return from the engine to the tank, it's more likely the "wet-sumping" has another cause elsewhere.

Hth.

Regards,
 

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Discussion Starter · #4 ·
Thanks! So this is the correct tank.

You're not quite correct about controlling oil flow. For any given pressure, the volume going thru is controlled by the orifice. Think about a garden hose and how you can control the rate of flow (at constant city pressure) by changing the area of the nozzle.

Symptoms of wet sumping are smoky exhaust (both sides), oily wet plugs, and often a bit of smoke coming from engine seams in an otherwise tight dry engine.

So -- I went ahead and drilled a half-inch hole in the top of the tank so I could get at the top of the pipe. I drilled the orifice out to 7/32", the full i.d. of the pipe. Buttoned everything back up and put a long vinyl tube on the rocker-feed tee. At idle the oil gradually climbed to about 16" above the rockers, at which point I figured there ought to be plenty of pressure for the rocker bearings. That translates to about 19 inches of head above the pump -- if it were water that would be .68 psi. Multiply by .88 (specific gravity of 20w-50) and the open-side pressure is about .6 psi. Maybe if I'd waited another few minutes the oil column might have gone higher.

So I reconnected the rocker feed tubing, sealed the hole in the top of the oil tank with a half-inch bolt through a thick rubber washer, measured the dipstick, and went for a 30-mile loop.

Result: no smoke, dry plugs, no fall in dipstick level.

So maybe I've got this licked. If it recurs next week or next month . . .

I am amazed that my amateur rebuild produced a no-leak motorcycle.
 

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glad you got it sorted - i am no expert on pressures / volume flow -- my thoughts were that the pump at a given speed will deliver a fixed amount of oil - all this goes "up the pipe" - some to the tank some to the rockers - the bigger the hole in the tube to the tank the more oil goes into the tank and less to the rockers - but the total oil remains the same - but i could be talking [email protected]
 

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Discussion Starter · #6 ·
I'm not an engineer and my hydraulics aren't bulletproof but some stuff to think about:

The oil pump has a bore and stroke of about .5" x 1" which would be displacement of .25 inch. At 4000 rpm with no resistance that would pump about 1000 cu in a minute or about 4 gallons, which is ridiculous. However we know that in the stock setup this volume has to pass through a 3/16" orifice at the top of the return pipe, which is .007 sq in, and let's say the rocker box feed pipe is the same, so this side of the system is pushing oil through .014 sq inch (smaller at the rocker bearing passage) at maybe 2.5 psi at cruising speed (above atmospheric pressure). Now I've opened the standpipe orifice by 33%, so at whatever pressure the pump makes at any speed about 33% more oil should come out of the sump and into the oil tank. Apparently, even if the pressure to the rocker feed has fallen a bit the volume seems sufficient to keep the top end happy. The stock oil pump at idle is supposed to push 10 to 12 inches of head pressure to the stock orifices -- I seem to be getting at least 50% more than that with an enlarged orifice and Morgo pump.

Anyone happen to know how many quarts of oil circulate through the oil tank each minute? We know that the other side of the pump pushes oil through the crankshaft at 60 to 80 psi but I don't know what that means in terms of volume per minute.

BTW I was worried about any swarf washing into the oil after all these operations plus break-in, so I borrowed an idea from my Guzzis and epoxied a strong magnet to the outside of the oil tank drain plug. It magnetizes the steel plug. At the next oil change I'll see what collected.
 

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So to interject a different view point. Your bike has fault, instead of finding and fixing that fault you got around it by modifying a system that works perfectly well on every other 63-70 650cc and likely 500cc bike?

Not sure about that one.

Rod
 

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Hi PA24-250, Very interesting solution.... Generally the modification you did would lead to oil starvation to rockers. Will see what happens. Please keep us updated.

Regarding Morgo pump, did you install piston or rotary?

Regarding the feed side of pump, since it's a positive displacement pump the feed volume is pretty consistent at all pressures. Is the same with return piston, the volume is a product of bore/stroke.


A severely worn drive block can cock in plunger head & skew volume, even with a good pump. It would take more than the wear limit shown in shop manual though. Best practice is a new or unworn drive block when pump is replaced. Even new parts must be checked for clearance.

Assuming the new gasket is correct & good (which it should have been verified correct on assembly), I would expect the return side of pump is not working properly. Again if the drive block is good. New pumps must always be bench tested as shown in shop manual. Even the slightest drop of oil in port is a failure.

In this case I would also do vacuum test on scavenge pipe to verify no leaks there or in case. Both pump bench test & vacuum tests are the real deal & actually tell you something. A good pump will show good 20+" in a few moments. A good pump sucks really well. I will hold well also.

It is possible someone modified the oil tank by making the rocker feed hole larger? I've not personally seen that done though. A larger rocker feed hole would recirculate too much oil into sump via rocker shafts & could cause this.

If your pump tests good the problem is in tank orifices. Enlarging return orifice to tank is a risky proposition. Triumph had this formula figured out for many years & it works good on thousands of bikes.

Most curious as to the long term effects of your modification. Might work really well, but what is the root problem?
Don
 

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I'm not an engineer and my hydraulics aren't bulletproof but some stuff to think about:

The oil pump has a bore and stroke of about .5" x 1" which would be displacement of .25 inch. At 4000 rpm with no resistance that would pump about 1000 cu in a minute or about 4 gallons
No...your logic is incorrect, because there is a gear reduction between the crankshaft pinion cog and the inlet camshaft. When the motor is doing 4000rpm the oil pump is doing something less. I thought it was half the crank speed from memory but somebody else here will know the real answer.
 

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Discussion Starter · #11 ·
It's the Morgo piston pump. Before installing it -- and a new oil pressure valve -- I cleaned and tested all the oil pipes and passages, including the the scavenge tube. I followed all the instructions in the wet-sumping section from the original Triumph shop manual. There's only one listed potential cause that I didn't test for was a porous crankcase, because I don't know how and wouldn't replace the case anyway.

One of the first things I tried was to run a soft iron wire up the return tube to clear out any detritus, and in fact that improved the situation a bit. So the next step recommended in the original factory manual is "using a hand brace . . . and 7/64"and 15/64" drill bits, run the drill bits into the return tube and rocker feed tube at the top of the reservoir to see that both tubes are free from internal burrs and restrictions that can occur at their welded joints." That's exactly what I did (except that I had to drill thru the top of the oil tank to get at the top of the tube). In fact the 7/32" bit I used is SMALLER than the the factory-recommended 15/64" bit. So my mod is perfectly in line with the factory recommendation. And frankly the manometer test I did on the rocker feed tube convinces me that the rockers will get all the oil they need. The factory recommends at least 10" of head above the rockers, and I have 16". Of course I'll monitor wear on the valve adjusters etc -- and if they go dry I'm prepared to block up the orifice again or buy another tank on ebay for $125.

I read up on oil return issues pretty widely in the various Britbike forums and it's appears common to fool around with changes in backpressure on this pipe, whether to cure wetsumping or push more oil to the rockers. I've seen people put more restriction on that pipe-top orifice, or put check valves on the rocker feed tube, or any number of other mods.

Devotion to mechanical purity on these machines is amusing. By that standard the Morgo pump is inauthentic. Would you spend the rest of your career readjusting Lucas points because Boyer hadn't been invented when your bike left Meriden? Would you stick with 30-weight oil because the original '50s-era manual required it? Have you ever used Emgo parts instead of NOS? Everything on these bikes should be up for improvement.

I'm not a restorer. I build my bikes to ride. When I got it, this bike had been rusting for 40 years and half the parts had to be thrown out. By Italian bike standards I thought a lot of the 30s-era Meriden engineering looked Mickey Mouse -- I've rebuilt and ridden Guzzis, Laverdas and Aermacchis. I replaced ALL the Lucas bits with modern stuff including my own wiring. So now that the wet-sumping is finally (I trust) resolved, I have a more or less reliable daily rider and that's exactly what I'm doing -- riding it daily.

Rant over. Sorry for getting carried away. I admire folks who restore bikes to Meriden-original standard. I'm just not one of you.
 

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Hi,

You're not quite correct about controlling oil flow. For any given pressure, the volume going thru is controlled by the orifice.
Uh-uh, you aren't getting my point - "what would be a requirement to 'control' the flow of oil returning to the tank from the engine?". Also, your "garden hose" analogy is not correct - the scavenge part of any oil pump has a greater capacity than the feed side; in normal operation, the scavenge part of the pump pumps oil-air-oil-air-etc. depending whether the end of the pump pick-up in the sump is submerged in oil or not; once in the pipe, the air compresses. Even if there is a sufficient quantity of oil in the sump when the engine starts for a continuous stream back into the tank, the aforementioned greater scavenge capacity will pump out the sump faster than the feed side of the pump can fill it.

Symptoms of wet sumping are
I'm well-aware of what the "Symptoms of wet sumping are". But again, you aren't understanding what's been written for you - "there is nothing certainly in a standard unmolested tank that would affect oil return from the engine to the tank" - i.e. your bike's tank would have to have signs of being "molested" by a dpo - e.g. the hole in the return pipe welded to a smaller diameter? - to cause wet-sumping by preventing the oil pump scavenging the sump contents back into the tank.

The oil pump has a bore and stroke of about .5" x 1" which would be displacement of .25 inch.
Less than 0.2 cu.in.

At 4000 rpm with no resistance that would pump about 1000 cu in a minute or about 4 gallons,
Depends:-

. As "tridentt150v" has alluded, the oil pump is driven by the inlet camshaft pinion, so it's running at half engine speed - only 2000 rpm @ 4,000 crankshaft rpm.

. However, it depends whether the pump is single- or double-acting - pumps on the up or down stroke, or both:-

.. if one, the scavenge has the capacity to pump a little under 400 cu.in. @ 4,000 crankshaft rpm - a gnat's under 1.7 US gallons;

.. if both, double;

.. however, the calculation's irrelevant because the scavenge can only pump as much actual oil out as the feed pumps in; the rest of the scavenge is air.

We know that the other side of the pump pushes oil through the crankshaft at 60 to 80 psi but I don't know what that means in terms of volume per minute.
Very little on its own. Pressure on the feed side is a result of big-end bearing clearance, temperature and viscosity of the oil. You would then also need to know the volume (bore 'n' stroke) of the feed pump.

Hth.

Regards,
 

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More simple logic than a devotion to anything. You rebuilt the motor, it now has an issue and instead of finding the issue you decided that somehow that issue must have been there since 1970. Crude or not if the return orifice in the tank were an issue we would all be wet sumping.

Rod
 

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I'm not an engineer and my hydraulics aren't bulletproof but some stuff to think about:

The oil pump has a bore and stroke of about .5" x 1" which would be displacement of .25 inch. At 4000 rpm with no resistance that would pump about 1000 cu in a minute or about 4 gallons, which is ridiculous. However we know that in the stock setup this volume has to pass through a 3/16" orifice at the top of the return pipe, which is .007 sq in, and let's say the rocker box feed pipe is the same, so this side of the system is pushing oil through .014 sq inch (smaller at the rocker bearing passage) at maybe 2.5 psi at cruising speed (above atmospheric pressure). Now I've opened the standpipe orifice by 33%, so at whatever pressure the pump makes at any speed about 33% more oil should come out of the sump and into the oil tank. Apparently, even if the pressure to the rocker feed has fallen a bit the volume seems sufficient to keep the top end happy. The stock oil pump at idle is supposed to push 10 to 12 inches of head pressure to the stock orifices -- I seem to be getting at least 50% more than that with an enlarged orifice and Morgo pump.

Anyone happen to know how many quarts of oil circulate through the oil tank each minute? We know that the other side of the pump pushes oil through the crankshaft at 60 to 80 psi but I don't know what that means in terms of volume per minute.
Hi PA,
If the oil pump was capable of moving 4 gallons or even 1.7 gallons of oil with the engine at 4000 rpm, it would be fantastic.
Unfortunately the pump is just not designed that way.
The calculations made so far have been made on the assumption that the pump is symmetrical in operation and that what is drawn into the pump from the sump on the downstroke, is then pumped back out of the return line on the upstroke. To do this, the pump would require two ball valves, one for inlet the other for outlet. Unfortunately the Triumph/morgo pumps have only one ball valve on the outlet. The other valve is a piston port, very high up the bore of the pump, this results in a pump that is asymmetrical in operation.
From the top of the stroke, the piston port is covered and the decending piston creates negative pressure pulling the outlet ball valve hard on to it’s seat, with some help from the ball return spring. The port is uncovered by the piston and as the piston coninues to decend oil and air is drawn into the bore.
The effective downward stroke will be the from the port to the top of the piston at it’s lowest point. Not the entire length of the stroke. For arguments sake let’s say 0.175 cu.in.
This is great it is actually quite a lot, enough for the pump to lift oil from the bottom of the sump, even if it is aerated.

Now the piston starts to ascend, and the pump pushes most of the oil it has just lifted, straight back out of the open port and into the scavenge pipe again. Once the piston closes the port on the upstroke, the remaining oil is forced past the ball valve and into the return line. If you measure the distance from port closure to top of stroke, it is only (very rough guess) 1/16 “ (0.625") and 1/8” (0.125”)
Flow now would be onle 0.4-0.8 gallons a minute at 4000rpm.

But, as Stuart has previously stated, you can only take out what you put in, so in reality the oil that passes out of the return is the same that is put in by the smaller diameter pressure piston. So we have been making the calculations on the wrong side of the pump.
The difference in volume on a standard pump is 30% between pump and scavenge sides.
With this in mind, there will be only 0.3 to 0.6 gallons passing back to the tank per minute at 4000rpm.

Of course I do not know the effective pressure stroke exactly, and I am working from memory/guesswork only, so the flow calculations are only indicative of a lowered volume flow rate.

I do hope you have cured your wet sumping issue and are out there having fun on the TR6.

Regards
Peg.



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