Adjusting oil Supply

[Willgo]

GT380 1971.
Read a lot about reducing the oil supply from the pump when using a modern oil in these forums, which makes sense to me.
But looked though my manual and can’t find anything on adjusting the pumps out put.
So how do you do it.
How do you know how much it is supplying.
The lists I have read talk about 40-1 or even 80-1, how does that equate to the pumps out put.
Thanks for any advice.
Bill Dag.

[Suzsmokeyallan]

The pump has a cable or linkage and alignment marks on it for setting the delivery. You are not actually changing the total output as per say, just changing the amount of oil as its delivered within the lower rpm ranges.
The pumps deliver according to throttle movement, so if viewed on a graph, they have an increasingly metered output slope upwards to around half throttle, but in the wider open settings the delivery is basically fixed at one constant setting within the pumps design.
So you need to start at the stock setting and then access what you need to do from there. You are basically changing the 'timing output' of the pump in relation to the lower range of rpms.

The pump always delivers oil, even at the full off on its lever setting, so lets say the pump delivers oil at 10% at full off and 100% at full on, the way its set up at the factory, the lever is set above the full off adjustment.
Therefore retarding the stock lever setting at idle closer to full off position reduces the amount of oil to some degree and retards the oil delivery output slope within the lower rpms.
The old oil from the 70s was supposed to be metering at somewhere around 20:1 ratio on these pumps according to Suzuki but with modern oils that would not be correct due to their performance characteristics flowing through the system..

32:1 is more commonly used nowadays on the modern oils as a standard premix ratio and while it does not seem to be much of a difference, in some engines re-jetting is needed to use it going for a 20:1 ratio.
The GT could never deliver 80:1 by the stock pump unless it was drastically modified and it would be pointless anyways.

[Barry S.]

I think there is a misconception about 20-1 ratios in the 70's, that is a premix ratio for dirt bikes, 1 quart to 5 gallons gas. If a bike with a pump used that much oil it would use a quart every tank and a half of gas. 80-1 would be a quart to 20 gallons gas or around 6 or 7 tanks full, sounds about right to me.

[tz375]

We have no idea what ratio an oil pump on a Suzuki equates to so it's not relevant. One could calculate usage of oil over a period of time and compare that to fuel usage and compare the two results to work out an average oil:fuel ratio but it doesn't mean anything.

20:1 or 32: 1 are ratios that relate to fixed pre-mix ratios for off road bikes, race bikes and really old 2 strokes.

On a GT750 the feed to the crank bearings stays basically constant, but as Allan pointed out, the cylinder side rises from zero output at closed throttle to 100% by 37 degrees rotation (close to half throttle) and from then on remains at the same 48cc/hr at 2166 rpm. So at full throttle, adjusting the pump link or cable makes no difference. At throttle openings we normally ride at 0-1/2, backing the adjustment down will decrease the pump output because the pump stroke will be less than stock at any small throttle opening.

[Willgo]

Getting a little lost here guys my preconception was I would be adjusting some hidden volume screw can see that’s not so.

I thought I understood from Suzsmokeyallan post that setting the oil pump operating arm further “back” would supply less oil in the early stages up to the point it comes onto full output, which again if I understand correctly is some where near ¾ throttle.
So starting the metering lever operation later will also bring it on to full output earlier in the throttle range.

So the way I see it you don’t really reduce the supply much at all by this method in fact you may increase it.

But I have read on one of the Suzuki 2stroke forums that people say they have reduced the pumps out put when using modern oil. Stating lower oil consumption, less smoke and drastically reducing the oil that collects in the silencers/mufflers.
The ratio being calculated by how much oil they get though against petrol consumption.

Sorry if I haven’t caught on to what’s been said but as I mentioned before my only real experience of 2Strokes was back in the days of Mr Villiers engines.
Regards Bill Dag.

[Suzsmokeyallan]

If you set the pump lever further back towards its rest position you will reduce the volume of oil consumption.
If you advance it to the factory mark or more you will increase oil consumption.
Remember at cruising speeds in high gear on level ground you may be only at or less than 1/8 throttle. This equates to oil consumption reduced in a percentage thats only able to be realized in calculations by the miles traveled per CCI tankful.
It does not take much reduction of the oil pump to see the difference at the slower throttle settings in the way the plugs burn and how the exhaust ends look.
Allen Wood and myself on Buffalos, his is a 74, mines a 76, run our pumps at or near to the rest position and have perfect plug readings with near dry baffles.
I use Shell Snow Ultra and Allen will chime in here on what types hes used, but I know hes used Suzuki CCI oil a lot.
Allen has logged over one hundred thousand miles with his 74 buffalo set up this way and reports no oil related issues.
I've used mine in summer trips into B.C and have had no oil issues in the last 10,000 miles or so since I got the bike in 2007.
The way mines set up, the engine has actually gotten smoother and faster, plus its now cleaner in the pipes, exhaust ports and combustion chambers compared to when I first got it.

[Barry S.]

Mine is cut back as well, not bumping the rear of the housing but about half way back. I got about 1000 miles to a tank full before the oil level got to the sight window. On that trip one of my exhaust flange bolts stripped out letting oil blow out around the header, I still have oil stained jeans from that trip, it was really puking out the oil, plenty to go around.

[tz375]

Willgo,

I think we all understood what you were saying but maybe didn't explain it all that well.


As you can see form the diagram, the pump reaches full volume when the arm is at 37.2 degrees or a around half of its travel. So any small change in arm angle by adjusting the cable (J/K models) or the threaded rod (L/M/A models) will pump less oil at anything under half throttle which is where we do most of out riding.

The calculation of total oil consumption over a fixed distance compared to fuel used over that same distance is interesting but can't really be compared to a fixed ratio like pre-mix. The reason is that it's an average consumption rate which is very different at low and medium speeds compared to a pre-mix. In fact we have no way of knowing what the actual ratios are at different speed and load conditions though we can speculate all we want.

Adjusting the arm will reduce oil consumption and the amount of unburned oil and will create less smoke at the risk of having less protection when you need it. Eric's logic was that a better grade synthetic oil has more protection at the limit and therefore he could use less oil and go back to say the original design level of protection with less of a better oil.

That is not bad logic but it ignores other factors, such as ring sealing and heat transfer, both of which are significantly better with MORE oil. The late Gordon Jennings tested different pre-mix ratios and found that less oil meant less power and more scuffing. More oil gave more power and a cooler running motor. Not everyone agrees and there are tales form back in the day about Jennings motors fouling plugs and so on. performance Bikes in the UK did somewhat similar tests with different oils and came to the same conclusions.

On the GT that is probably less of an issue because backing the adjustment down makes no difference at full throttle, so the power at WFO will be the same, so it comes down to a choice of how much protection is enough. I don't do a lot of miles but I tend to ring its neck at times and I hate rebuilding seized and burned motors, so for me, a good smokeless oil is good at stock settings. For the rider with more restraint who does lots of miles, maybe backing off the adjustment makes sense.

[Suzsmokeyallan]

Richard I like your reply but totally disagree with you on the more oil is better. I like reading books for reference material but I prefer real world testing/results which give me the direct testing and results I need for confirmation.
If I may use the following examples as a reference this may shed some light on the oil issue. For this reference these engines use premix and are of between 25cc to 32cc two stroke air-cooled motors.
They are highly stressed and running at or near full rpms all the time, so we are talking about grass trimmers, chainsaws and leaf blowers here.
These tests were done over a period of at least six months on each premix, so there was time for long term results to be seen and not just a seat of the pants short term speculation.
Since you can't physically rejet these diagram type carbs, any rejetting mods are basically to fine tune the high and low speed needles and a mixture screw if fitted.
If I use a 32:1 mix, the engines run flawlessly with clean burning plugs, no loss of power, no carbon build up on the crown or exhaust ports or sticking or gummy rings.
If I use a 50:1, the results are similar but I find the engines run a bit hotter and I have to go to a colder range plug. Once I do this the results to the 32:1 mixture is almost identical but the 32:1 is still better all round performance.

Now if I go to a 20:1, I imediately find theres a loss of freeness to the way the engine builds power in the lower rpms. No matter what I do, the exhaust outlet stays wet and the plugs foul faster. One one engine the exhaust port will close itself off completely with carbon and stop the engine from working after a few months. Rings were stuck in the grooves on that piston and it showed serious blowby staining with scuffing on the skirts.
One this one particular engine the exhaust system is a two piece unit that you can open and clean, it was full of wet carbon so if the exhaust port didn't stop it, the clogging pipe would have.
16:1 although I didnt try it, it would only worsen this issue and cause the above issues to happen quicker since as the ratio of oil got higher the fouling and carbon deposits got worse.
The verdict from this is that more oil is actually not always a good thing, it may well work in some applications but not in any of the ones I've seen so far.

Lets take a look at the 76 GT now, It was running pretty lousy when I got it, any attempt to ride it hard had it leaving a constant smoke cloud and you could smell fuel vapours been blown out the airbox intakes as you rode it, obviously the engine wasnt breathing properly.
The pipes were caked in wet carbon, the ports and crowns had a wet layer of carbon about 2mms thick on them, and the baffles were clogged with thick wet carbon.
All I did was basic maintenance to it and a tune up, but I didn't find anything wrong with the settings as I got it. I cleaned the baffles and dialed back the pump and rode the stuffings out of it to try and clear it off.
I figured a good few rides on the open road blasting it to the max on long uphills would shake it up for sure, but it was just too much residual carbon for a few runs to fix, and lets face facts, a stock Buffalo isn't fast so its not going to scare me.
Now many many miles later it finally runs as it should and all the carbon has finally been burnt off the pipes and piston crowns. The exhaust note even sounds different now, its more pronounced in the way each pipe 'blips' its tone at idle compared to the subduded mumble it had before.
This audible difference alone would tell me compression was low before, due to sticking rings from carbon build up. While my results suit me, everyone elses will be different and they have to be acceptable to suit them.
However I have never had an engine hole a piston or seize on me and I ride them hard, no babying involved here unless its a cold engine and I always let them warm up first.

You Sir say tomato I say tomato.

[tz375]

Dear Allan,

You are indeed entitled to your opinion. It just happens to be wrong.

Anecdotal evidence about clogged pipes is not scientific evidence about the power that a good motor (one in good condition) will make with different oil ratios.

In the case of that small engines you found that 32:1 was "better" than 50:1. That doesn't mean that in that motor 20 or 12 or whatever to one will therefore be even better than 32:1. There is an upper and lower limit to all parameters and in that case it appears to be somewhere between 32 and 20. Similarly, just because one TZ motor was best at 16:1 doesn't mean it would work at 12:1. And none of those results can be extrapolated to a GT750 operating on the street at relatively low levels of power and stress and at far higher oil:fuel ratios.

It's a case of working with a particular motor, preferably on a dyno, to work through what is happening.

I didn't suggest that anyone should be running their GT at the equivalent of 20:1 or whatever. I just raised the issue that in general more oil is better. A GT operates somewhere around 60 or 80:1 on average. Should you set it up to run with less oil? I wouldn't but I know people that do and that's their choice.

[Suzsmokeyallan]

Richard if my opinion according to you "just happens to be wrong", yours is downright ridiculous, and I'm leaving it at that.

[tz375]

So I forgot the smiley. I was running late for something . It has been inserted.

If there are facts or interpretations of issues you would like to discuss that's fine, let's talk about them. I only know what I know. I don't know everything - far from it. I grew up where healthy debate is usually a good way to get to the root of an issue and to test ideas.

Please explain what is ridiculous about the "more is more" idea. What I tried to explain in short form, were the results of at least two studies that I know of and not simply my idea. I fail to see what is ridiculous about that. Eric and I often disagree as the causes and effects, but we can always talk about the ideas and can always agree to disagree.

But let's talk about that GT for a moment. It had an exhaust and air filter soaking with oil by the sound of it and over a period of time you managed to burn off a lot of that crud. Less oil on the baffles and less coating the pipes surfaces will produce more power and a less muted exhaust. One interpretation was that the difference was the oil pump setting. That no doubt contributed, but what happened was that you rode it harder and burned off the surplus oil. That improved performance. Would the same result have been achieved with the original oil pump setting and riding hard? Who knows - but probably. If the oil pump was cut off, the oil would only burn off by running the bike harder. That was what cleared the pipes out - not the pump setting. To add to that hypothesis, consider that if you rode the snot out of it as you said, it would have been running over 50% throttle and the pump would have been at WFO. In other words, the pump backed off helps at lower speeds and throttle openings but was not the cause of the bike running better.

Changing two variables always makes it hard to determine what the underlying mechanism for change was. Agreed?

[Suzsmokeyallan]

I'll humour you on your smileys Richard, so lets revisit the scenario on the GT

Think of these variables, as you know the oil is delivered by the pump in a gradual increasing slope up to a point where after that its output is fixed.
This bike got ridden in the lower throttle settings often and so the delivery output of the pump was mostly in the lower settings of the pumps output.
So from looking at what I saw, the bike was obviously ridden mostly around town, in this case it was Calgary, prior to when I got it.
I found this to be the case in fact after asking a few questions about its previous owner and where it was ridden.
NOW if this is the case, the oil pump was delivering oil at the stock setting and mostly at or under the wide open throttle delivery output.
So what did this do to this bike, it was choked up with unburnt oil, aka carbon, because it was getting too much oil and nothing else, theres no secrets involved.
According to you this should be good, more oil is good, but it isn't good at all, its actually worse.
As you know the CCI system is superior to anything else ever built for lubricating a two cycle engine and its really two systems.
The oil going to the lower mains does not stay there, it mixes with the incoming charge and the upper case intake delivery lines to give a TOTAL oil mixture percentage.
However in the case of a two cycle engine with a pump, the amount of oil delivery at lower rpms needs to be carefully set, if theres too much oil at lower rpms the engine will build carbon, not enough oil and it could seize.
Suzuki knew this and designed the pump to be a variable output device, a lesser output for the lower rpms, slowly increasing it to a higher fixed ratio for the higher rpms.
Two stroke oils have changed so much since the 70s and 80s and so have their ability to lubricate and burn off almost completely leaving virtually no residue.
I don't doubt for one minute the Shell Snow ultra has played a major part in ridding the engine of the large quantities of wet carbon it had, but the amount of oil delivered has been changed now too.
So at the lower rpms the engine is now getting the right amount of total oil percentage it can deal with AND be able to burn it off completely.

[tz375]

Now I see what your logic is. At low speed/throttle settings putting around town, you believe that stock settings create too much oil in the pipes and carbon on ports etc.

I am saying that what cleared that excess oil from the mufflers etc was probably two things. Change to a cleaner burning oil prevented or reduced build up and running it harder burned it off. Running less oil at low speed may arguably reduce further build up but it doesn't burn off teh existing deposits. What burns off the old crap is lots of hard miles. It was principally the change in rider and riding style that burned things clean. Modern oil probably contributed to not coating teh surfaces again but I'm less convinced that reduced oil supply was much of a contribution.

What I'm saying is that reducing pump output may or may not help to prevent recurrence of that oil build up, but it won't clear the old stuff out. Only heat does that and that comes from riding harder.

That creates the interesting hypothesis that Suzuki designed the oiling system for bikes that were ridden as long distance tourers/stop light to stop light "racers" which was how people tended to ride them when they were new. Now riders tend to be older, speed limits are enforced with stiffer penalties and the average GT750 is probably ridden only/mainly at lower speeds and you believe that the oil output for bikes rifdden that way could safely be reduced.

That may be right. As long as the motor isn't spending most of its time at low throttle high heat conditions such as parades in Arizona for example, you will probably be fine. More oil is always better for power - but as I mentioned earlier that's at WOT, not phutzing around on a 1/4 throttle.

Bottom line: Good modern ashless, smokeless oil is a great investment and will make less of a mess than dino oil but costs more. Ride it hard to burn off the crap and you should be good. Oil is relatively cheap for those of us doing very few miles a year.

[Suzsmokeyallan]

Ok Richard now I see where your logic lies for "more oil is better", you are looking at WOT applications, but even then thats not always 100% applicable either.
Gasoline molecules can only attract so many oil molecules to them, after the set quantity of gasoline has been saturated, anything you add over that point is merely sunken to the base of the container and not held in suspension.
Even over time, the oil will release itself and separate from the fuel mix as well, and that why you never mix more premix than you plan to use.
So where do you stop at the point of having too much oil in the mix, its obviously related to a sensible ratio of premix and how well the engine can handle the incoming charge to burn it off completely under constant high rpms?
The thing is, contrary to what many would believe, less oil in the premix gives a richer running condition and more oil gives a leaner running condition.
So why is this? well because its premix, it HAS to pass through the carbs jets and its all to do with how many gas/oil molecules can pass through a set of fixed restrictive orifices.
An engine using an oil pump does not have this issue since the oil is added after the carbs on the intake tract or crankcase.
That is why you need to re-jet when changing premix ratios, for example as you would know, running an engine jetted for a 20:1 and then switching it, to a 32:1 ratio you will need to open the airscrews, reduce mains and drop the needles.
Because the oil percentage with the gasoline mixture is now reduced it can now flow more easily through the same sized jets giving the engine a rich jetting condition.
A WOT setting will be found almost constantly on a race motor navigating a track but not in day to day driving conditions where the heat and burn rate within the engine is reduced.
Again as you know they never let the two stroke race motor idle, mainly for keeping the cold range plugs from fouling and the to keep working engine heat constant.
A street motor has to idle, sit in traffic and still be expected to reach its designed redline when need be, all extremes in one package.
On the CCI system such as the GT 750 it can be dialed back to give less oil in the lower rpms simply because the modern oils are better at what they do and also flow better as well. You do not need as much as once was thought necessary so you can change the timing of the pump to suit the oil.
It may seem a lot if you casually glance at it and say, 'so much less oil'??? it should seize surely, but its actually so minimal, the only real guide is how the plugs burn around their perimeter.
I'd also say some oils build carbon regardless of the ratio, while others do not, and some leave virtually no residue whatsoever or have the ability to remove carbon.
Castrol 2T from the 70/80s was a good example of a carbon building oil while the Shell snow ultra I use in the GT is a great oil for ridding the engine of deposits.
Conclusion: now you have clarified the WOT application and I have clarified mine, lets agree to agree on the fact in the relative conditions spoken about, we are both right.