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Joined: Jan 2017
Posts: 637
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Senior Contributor
Before I start up my ancient Pope 320 rotary valve engine, I just wanted to double check the correct fuel mix.

In my Victa Mayfair I use about 120ml semi-synthetic to 5 litres. The manual says 200 ml to 5 litres, but I'm guessing that would be the old mineral oil not modern semi-synthetic?

But the manual for the Pope 320 engine says 1/2 pint to 1 gallon, which translates as 284.131ml to 4.54 Litres. That is nearly twice as much as what I've been using in the Victa!

I am sure they were talking about mineral oil in those days, so maybe with semi-synthetic you would not need that amount?

Can anyone please clarify the correct mixture for both Victa Mayfair and Pope 320. I'll be using the ByNorm 2 stroke oil, which I gather is semi-synthetic?

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SENIOR TECHNICIAN
I would run 25:1 (40ml per L) in both. Depending on the age (I remember you saying about a rubber snorkel so I would say pre 1976 on the mayfair?)

The reason being that many of these engines have bushings instead of roller bearings (especially on the little end).

40:1 is pushing it, but I doubt you would have done any damage unless it is being run full throttle through 2ft high grass day in day out.

The oil you are using is of decent enough quality, so don't worry about carbon build up.

Joined: Jan 2015
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Junior Technician
hi VM,
it's 16 to 1... for your Pope read the manuals.....

The old British Seagul outboards ran at 10 to 1....
you just do that
cheers
speedy

Last edited by speedy; 27/06/22 07:05 PM.

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Speedy, The Pope manual for that model states 62.5 to 1. See my screenshot from the manual posted above. Bit of contention on Google about how many ml there are to a pint exactly, so around about 61 to 1.

16:1 seems a bit light on the oil to me.

Think I will go with Tyler's suggestion of 40 to 1 using a modern semi-synthetic (ByNorm) and see how she goes.

Last edited by vint_mow; 27/06/22 07:49 PM.
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Vint mow, the manual says 16:1 but that is due to the really poor oil they used.


I DO NOT SUGGEST RUNNING 40:1 in it. Its asking for trouble in the mayfair, let alone an older Pope.

Edit - I now read it as you are saying 40:1 as 40ml to 1L.

I recommend adding 40ml of oil per L of petrol. This gives a ratio of 25:1

You must use 200ml per 5L jerry can

Last edited by Tyler; 27/06/22 07:48 PM.
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Yes 40 ml to 1 litre, what else could I mean? Haha!

That's 160 ml to 4 litres or 200 ml to 5 litres.

Last edited by vint_mow; 27/06/22 07:53 PM.
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Ok, we are on the same page.

The way I read the sentence to begin with was

Originally Posted by vint_mow
Think I will go with Tyler's suggestion of 40 to 1 using a modern semi-synthetic (ByNorm) and see how she goes.

hence the literal 40:1 is equivalent to 25ml to 1 litre. 100ml per 4L or 125ml per 5L

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Hi Vm ,Tyler and Speedy

The problem is if the standard specs are 16 to 1 and you run 25 to 1 the fuel mix will be overly rich as the
carby is set for 16 to 1.

I ran 25 to 1 on my Pope but it sounded like it's over fuelling down low ,I was going to try 20 to 1 next time with
good 2 stroke oil but not with fully synthetic oil.

16 to 1 is 473.176 ml to 7,570.816 ml

Cheers
Max.

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Originally Posted by maxwestern
Hi Vm ,Tyler and Speedy
The problem is if the standard specs are 16 to 1 and you run 25 to 1 the fuel mix will be overly rich as the
carby is set for 16 to 1.
Morning all,
Why all the confusion about ratios.
The Pope ratio is 16 to 1...
Max, how can 25 to 1 make it it overly rich when 25 to 1 is a leaner mix?

Anyway VM, I don't run my Pope a lot so don't to mix up 4 or 5 lts. but just mix up 500mls. Just use calculator to find the correct amount of oil.
Bottom line VM, if the engine hasn't run for years, I'd put some oil down plug and turn engine over a bit to get oil all over rings and maybe some on bearings. There's a front crankcase plug, you could put some oil in. It will smoke for a bit, run gently .
Good luck with first start.... get pics.
speedy


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The confusion was my fault Speedy. I was just wanting to know how many mls to add to a litre and using ":" as shorthand for "to". I realize now that you were talking the other way around, i.e. petrol to oil, 16 parts to 1 part, hence 16:1.

Max can correct me if I'm wrong, but I think he is suggesting 20:1 (fuel to oil ratio), or 1ml of oil to 20 mls fuel, which is a fair bit richer (fuel-wise) than what the manual specifies.

To avoid any further confusion, I'll just go with what Tyler suggested: 40 ml oil to 1 litre fuel, 160 ml oil to 4 litres fuel, or 200 ml oil to 5 litres fuel.

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25 to 1 is a richer fuel to air ratio compared to 16 to 1.

16 to 1 is recommended when a car engine oil was used as 2 stroke oil so the carby jets etc are tuned for this ratio ,I don't
think 20 to 1 with good 2 stroke oil will harm anything.


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Anyway VM the 16:1 ratio I use. You put 62.5ml oil to 1 ltr petrol.
Let's get it going, get some pics.....
good luck speedy


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Thanks Speedy, Max, Tyler,

Seems a lot of oil to me, but that is what the manual specifies, doesn't it? I am sort of expecting a lot of smoke. I will ask the former owner of the motor. Pretty sure he was running it on half that and the motor is still alive today. It really copped a work out from him for many decades and never missed a beat the whole time.

It is interesting that on the ByNorm 2 stroke container, they specify a whopping 50:1 ratio as a "general" mix, which is only 25 ml oil to a litre of petrol. I am guessing that must be for the small, highly aspirated modern engines like whipper snippers? But now that I think about it, I am sure that is all my dad ever used in his Mayfair and the engine is still going strong today. So I really wonder if it matters all that much. I recall my father would often just take a guess when mixing and never had any problems with his 2 strokes. I never saw him measuring things accurately to the ml. Often he just had a small tin which was "around about right" and he would fill it up and tip it into the jerry can. If he got smoke he knew to add less next time, if the mixture seemed too rich he would tip in a bit more oil. Funny thing, when I was running the Mayfair on the ByNorm specifications it was blowing out a bit of smoke and an older relative told me I was putting too much oil in the mixture! So I'm not sure and totally confused now. Will do what the manual suggests and if too much smoke will cut back.

My feeling is that with a semi-synthetic oil of today you would not require as much as what the manual suggests, because it was written back in the day of old mineral oils. So as Tyler pointed out, I think 40mls per litre would be the most practical.

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Yes I wasn't saying you can't run 25 to 1 (200 ml to 5 Lt) Vm ,it's just that I did that last time with my Pope and
at 48 seconds in on the video on decelerating I can hear the motor over fuelling and popping noises from the muffler
so you can put more oil into the fuel mix to fix this or tune the carby to suit the 25 to 1 mix..




The problem with veering away from the recommended fuel/oil ratio is the carburetor is set up for the right amount of petrol/oil/air mixture, so if you significantly alter this ratio you will need to change the jets and carby settings to suit.

A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less. Aha! The volume of fuel has changed. The oil takes up some volume that the gas used to occupy, so your engine is getting less gas and needs to be richened up.

With the Pope it's the opposite going from 16 to 1 and then to 25 to 1 ,the jets need to be smaller.

STIHL recommends the following.

The recommended fuel-oil mix ratio for most small 2-cycle (2-stroke) engines in handheld tools is 50:1 when using synthetic 2-cycle oil.

You can use the 50:1 ratio with any synthetic, semi-synthetic or additive oil and all two-stroke handheld power tools unless the manufacturer specifically recommends otherwise.

There are some exceptions to this rule:

If you are using old mineral two-stroke oil without any additives, you may prefer thicker mix ratios of 25:1 or 33:1 to ensure adequate lubrication.
Husqvarna recommends 33:1 for 75cc and bigger engines in high-load applications

IT'S ABOUT THE OIL

The 50:1 mix ratio is thinner, i.e. has less oil, than those used in the past. Older tools had thicker recommended mix ratios of 40:1, 33:1, 25:1 or even 16:1.

, the reason for the shift from 33:1 or 25:1 to the thin 50:1 mix seems to be that newer engine oils lubricate better than old. New engine oils are synthetic, semi-synthetic or have additives that improve their performance so that less oil is needed for the same lubrication effect.

The more oil in gas, the better the lubrication. As oil has some downsides, the amount of oil is usually set to provide adequate lubrication. The oil content required for adequate lubrication depends on the oil type and additives, but with synthetic oils 50:1 should be enough.


While oil is necessary, it does promote engine fouling. Most engine oils burn only partially and not very clean in the engine, leaving a residue on the engine parts. This residue or deposits can cause engine issues.

The incomplete and poor burning of engine oil increases the smoke in the engine exhaust. This smoke consists of small soot particles and constitutes particulate emissions.

The more oil in the gas, the higher the emissions. As with fouling, the cleanest results call for as little oil as possible. The amount of smoking depends also on oil composition and engine operation point.


MIX RATIO IS A COMPROMISE

As you see, the choice of gasoline–oil mix ratio is a compromise between lubrication and clean combustion: there should be enough oil to prevent engine seizing and premature wear, but no more to keep the fouling and emissions down.

Note that the consequence of too little oil and inadequate lubrication (engine failure) is much worse than too much oil. Using a thick, oil-rich mix ratio like 25:1 or 33:1 is playing it safe, and was necessary with older oils and engines.

However, most modern oils and engines will be adequately lubricated with today’s oils at 50:1 ratio.

I would think on a mower like the pope over fuelling the engine would make the motor run hotter

Just wanted to explain how if you change the fuel ratio from standard it can effect your engine to run leaner or richer.

Cheers
Max

Joined: Jan 2017
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Thanks Max, I appreciate the explanation and the details

I had an interesting conversation with my uncle who was the former owner of the Pope engine. Now get this! He says he only ever ran it on 25ml of 2-stroke oil to the litre, and he first bought the mower in 1964. When the mower finally fell apart, he kept the engine and converted it to horizontal and used it to to run an air compressor right up until the 1990s. In all that time he only ever gave it 25ml to the litre. He said he ran that in all of his 2 strokes always and never had any problems. I told him what the manual said and he couldn't understand why anyone would want to add that much oil, even in those days. He said "You'd look like an old steam train coming along if you were to use 40ml per litre or more." All I can add is if he was going to kill the engine by using 25ml per litre, it sure has taken its time to die. :-)

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That's interesting Vm, 25 ml of oil to 1 Lt is 40 to 1.

I've had a few old Victa motors and the motor has compression and runs but the conrod clangs as the motor runs and
either the big end is loose or the Gudgeon bush is loose and that is a sign of too little oil in the fuel mix.

Some of the older engines need more oil in the mix so the low quality bearings get adequately lubricated or they
can prematurely wear out.

I have heard of some people running old Villiers 2 strokes at 32 to 1

There is a discussion here with old 2 strokes and fuel mix ratios .
http://www.saving-old-seagulls.co.uk/phpbb3/viewtopic.php?f=2&t=3561

For me I wouldn't go thinner in oil than 25 to 1 with old motors and would put the needle down slightly in the carby and that is with
Valvoline Outboard 2 stroke oil ,the main use of this outboard oil is for water cooled motors but this one is
also recommended for other air cooled 2 stroke equipment.

It just depends on the owner what mix they run as I've seen some people use old sump oil as 2 stroke oil, on the
other hand I don't think it's worth buying super expensive racing 2 stroke oil as some people do for a lawn mower.

Cheers
Max.

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Yes Max, my uncle was telling me that when he was on the farm in the early days there was no such thing as 2 stroke oil, just engine oil. Huge difference to today where we now have a large range of specially formulated synthetic and semi-synthetic oils designed for different applications.

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hi vm,
well did it start?
speedy


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Hmm, not sure about that. At least where I grew up, where the nearest town had 800 people, there was two stroke petrol sold at a pump. It was green, whereas “super” was red.

We’d buy 20 litre drums of two stroke oil from the same wholesaler who sold us engine oil and hydraulic oil as it was much cheaper that way.

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He can't remember it until later in his life. He lived way out bush and had very little money so probably had little choice but to use whatever he had, so what went in the car probably also went into the 2 strokes if they were lucky, otherwise they just got the recycled sump oil.

Speedy, this build has been so troublesome and expensive I doubt I will ever take on another complete restoration and renovation. I am still short of a number of parts with little hope of obtaining them any day soon. Pope parts are near impossible to get, so I have borrowed from Tecumseh, Victa, Briggs and Stratton, and even resorted to making some parts. I got on to a few N.O.S. parts but the seller was not very sympathetic and just threw them all into a flimsy box which fell apart during transit. As a result a lot of the parts got bent and badly scratched up and one part went completely missing. Today's paints are also bothersome as my first paint job on the handlebars went wrinkly and cracked overnight for unknown reasons. Yet I put the same paint on the hubcaps that same day and it went on perfectly. But then the fumes from the glue I used to fix the hubcaps in place reacted badly with the paint and overnight caused it to peel. I could not believe it. I'm still looking for a glue that will not react with paint. I later repainted both and had the handlebars hanging up, but for some reason the wire support decided to break, sending the handlebars crashing into the dirt and on to nearby rocks and pavers. So I had to clean it back to bare metal again. Third time lucky, I hope!

I rarely do renovations, least of all hybrid ones, but I wanted to do this for my uncle so he can at least see a version of his beloved old Pope back in near pristine condition. I am not doing it for myself, I am doing it for him. The lawnmower may never be started if truth be told. It all depends on how I feel at the end of it all. As this build has been so troublesome I am in two minds about ever starting it. All it takes is for a drop of fuel to land on the painted surfaces and days of work can disintegrate before your eyes. I've been there before! I may end up just placing it inside as an ornament and conversation piece.

I rarely restore vintage mowers to "as new" condition these days, just to working order. It is just too expensive and finicky and at the end of it all I don't feel like getting them dirty again. Once we use them, moisture gets in and promotes rust all over again. A moron came to paint the shed roof a while back and he obviously had no idea what he was doing, as he hosed upwards instead of downwards, sending an avalanche of water into the shed, and drowned a lot of my restorations in mud. This sent them instantly rusty. I only found out a few days later when I opened the shed and by that time the damage had been done. Spare parts too, all covered in water and muck. They will never be the same.

So, there are some I restore from time to time to near new condition and then keep in storage, others I start, others I just get going and never fully renovate but use around the place. No build ever turns out the same or for the same reasons. I dislike painting immensely and prefer to just tinker and get things going. The Pope was an exception. The few parts I managed to scrape together were all in such terrible condition that I felt they had to be restored.

I'll post up some photos when it is finished, but that may not be for a while. Rome was not built in a day. Persistent cloudy, rainy weather has once again put me well behind schedule.

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