When is too little, too little (oil)?

[FCM]

Thought I would post this in case there is anybody else out there who cannot obtain the popular oils for gas helicopters - Amsoil, Klotz etc.

I have been experimenting with a couple of very different oils in my G230RC Benzine camera ship over the last few weeks.

The first oil I tried was Silkolene Comp 2 fully synthetic (some may remember my posting on another forum) at 42:1 ratio using unleaded 92 RON petrol.
This oil seemed to work well at this ratio and the spark plug colour was grey with no signes of overheating or fouling.

I then tried Motul 800 which is an expensive road racing fully synthetic ester based oil from France. This oil is very thick in consistancy and is difficult to syringe out of the container even at our high ambient temperatures here. I would estimate that it is at least twice as thick as the Silkolene Comp 2.

The recommended ratio is 50:1 which I tried and found that the spark plug fouled and was always black and wet even with the engine fully leaned. After contacting Motul and receiving the info. that it is okay to run "trail bikes at 100:1" I have been gradually reducing the oil content to see what happens.

I am now on 70:1 ratio but the plug is still wet although I do have a very dark brown colour appearing which wasn't there before. Engine seems happy enough although I have only run 2 tanks through at this ratio.

I am wondering if it will be safe to reduce the oil content further to say 80:1 given that the plug at 70:1 is still wet? I am now debating whether to go back to the Silkolene at 42:1 or continue the testing with the Motul 800 in order to gain the benefits from running a lean oil ratio which I am given to understand should allow the engine to run cooler.

Paul.

[Billme]

I like the sound of the motul oil...I would stop changing oil now, since you are getting a good responce from the engine...There is a chemical reaction that takes place everytime you change to a different brand, and it effects the rings by making them stick...
I would try 75:1, and get a new plug..Get the engine running good, and just watch the plug...If the engine is running good and the plug is a little to dark,, cut the oil slightly, and don't lean the needles... Then watch what happens...A lite, to dark tan is what you want...Its ok for the threads to be a little wet(rich indication) If you have reach a limit on the oil, then you can lean the lowend 1/32 for that day, and check the plug when you go home..
You make small changes, and remember what effect it had..Thats how you learn the gasser:)

Regards,
Bill Meador,
Century Helicopters

[FCM]

Thanks for your thoughts Bill.

Unfortunately, I think all my testing is invalid as today I discovered that I have a pretty big leak around the carby insulator block. I thought the oil accumulation was from my tank over flow but on close inspection today, I can see that there has been a leak at this position for some time. It is pretty amazing just how well the engine has been running with this defect!

I have installed a new insulator block and noted that Zenoah have updated the design as it now has brass bushed mounting holes to prevent distortion on installation.

Have noted your comments re: changing oils making the ring stick so I will look out for this. This current engine is nearly due a top-end strip anyway so I will continue running it with Silkolene and watch the ring.

Regards,

Paul.

[FCM]

My engine was in a worst state than I thought. Found out yesterday that the cylinder base gasket has been leaking quite badly for some time. I had mistaken the oil accumulation as overflow from the tank which I had routed close by the engine.

I think this engine has been leaking at the cylinder since I installed it. Have removed engine and removed the cylinder. The leakage at the lower transfer port is quite obvious although the gasket was intact and I also found the piston ring to be partially stuck but no cylinder or piston damage evident. Combustion chamber and piston crown both coaked but cleanable. Bearings okay so will rebuild with new ring after cleaning.

I have just reassembled my spare engine's cylinder with a new base gasket using a petrol resistant gasket sealant to held prevent any more leaks at this location. This engine has yet to be run following a piston/ring change.

Any tips with re-building/breaking in? I will be using the Silkolene oil at around 40:1 ratio.

Thanks,

Paul.

[bigrcr]

I would recommend a non-synthetic oil for break in (petroleum based). The synthetic oil will not allow parts to seat as well as they should and the ring/cylinder on the Zenoah engines are quite hard. After break in (or really after a gallon or two of fuel), then move to the synthetic oil.
Naptha based fuel (camp stove fuel) will greatly help with keeping the motor cleaner for longer as well as using a not too rich oil/fuel mix ratio.
If this motor was leaking (sucking air) I would also recommend checking out the conrod bearings closely as they may fail shortly after reassembly from the rebuild if the motor had been running lean.

Later,

John

[FCM]

Okay, I guess regular mineral based 2 stroke oil will be okay for the breaking in period. Will 40:1 be a good ratio for this?

Will double check the con rod bearing but it did initially look okay to me.

I do not think that naptha based fuel is available here so it looks like I am stuck with the normal un-leaded.

Thanks John.

[bigrcr]

Probably, but It depends on the oil. I run Lawn-Boy ashless at 40:1, but initially used it at 32:1. I would probably err to the rich ratio at first and check the plug with a new oil. The main thing during initial break in is to ensure proper lubrication and to not stick the ring (being too rich ratio or too hot with a rich ratio). Let the plugs take the beating if anything is to take it. Don't require too much power/performance out of it for the first 1-2 gallons. I look at the initail break in as "lapping everything in". Then gradually start demanding a bit more of it at a time. Listen, the motor will tell you as it is ready for the next step. One thing is that the needle setting can be leaned a bit at a time from the rich side (the motor will actually ask for it). I know, I'm anal!

Gasoline will be just fine, just keep the octane rating low.

Hope this helps!

[FCM]

I'll take your advice and run the mineral based oil at 32:1 and see how the plug looks. Got a low ash oil that's made by Shell that I hope will be okay.

I do not intend to do anything but hover until the engine has loosened up. Will be running an engine speed of around 10,000 rpm which will give me an 1100 rpm head speed. Do not intend to run my GV1 during the break in period as this may mask any overheating problems.

Your help and guidance is very much appreciated John (and Bill) I just wish I that I had known one year ago, what I know now!

Paul.

[bigrcr]

Good luck to you and HAVE FUN! :lol: Let us know how things go.

Later,

[FCM]

Have now run rebuilt engine for 2.7 hours. Had two false starts when I had the cylinder leaking (again!) around its base but this morning, I can report no leaks at all.

First 2 Liters of fuel run through was mixed at 32:1 using Mobil 2T oil. Had the plug foul and engine cut.

Today I ran just under 2 L of fuel mixed at 36:1. Can still see plug wanting to foul but no engine cut today.

All flights have been limited to 2 1/2 mins with a 30 sec. ground idle cooling period between hops.

Am now unsure where to go with oil ratio. Looks like I have too much oil but the centre electrode looks too lean to me. Engine note in hover is fairly steady with a slight burp and tail wag every now and then. Have not wanted to lean any further due to the colour of the centre electrode.

Images taken from video so not very good quality I'm affraid.

Paul.

[Billme]

I would put a new plug in, and cut the oil to 50:1....The engine sound, and the tail kick every now and then is what I like to run....
With this oil your running now, what is the leanest mixture its design for?
Sounds like your doing good Paul....


Bill Meador
Century Helicopters

[FCM]

Hi Bill,

Since my last posting I have reduced the oil to 40:1 and then 42:1. I think the engine liked 40:1 best but still seemed to have plenty of lubrication at 42:1.

I have no idea what the minimum ratio for the Mobil oil is as there is next to no info. on the bottle and nothing on their web site.

I have now run this oil for 4.7 hours (approx. 7 liters of fuel) and have decided to switch to the Silkolene fully synthetic as I have been unable to get the engine to run cleanly or evenly on the Mobil and I hope that the running time I have put in has bedded in the new piston ring.

My problem with the Mobil is that as soon as I try to lean the engine to smoothen out the tail wagging, the centre electrode loses all of its colour and you can feel the engine getting hotter. The wagging and uneven engine running has actually cracked my silencer so I know that something is not quite right.

Will be testing with the Silkolene at 42:1 tomorrow morning and will post the results.

Paul.

[FCM]

Just returned from flying using Silkolene fully synth. at 42:1. Immediate improvement in the overall running and smoothness although when the throttle/pitch is reduced in the hover, the engine misses a bit which is not what I need in order to film.

The plug still has a very pale centre electrode and I should point out that this is the same plug cleaned up as I am running low on new plugs! I do know that Silkolene burns with a pale grey colour as opposed to the 'normal' light brown.

Obviously the Mobil oil was not a good choice for me to run in this engine and it has produced quite a bit of coaking on the piston and the exhaust. Ring has not stuck though hence continuing running/testing.

Next I tried running with the same fuel mix but with a 80% restrictor (see pic) installed in the carby insulation block opening. This had the effect of enriching the mixture and smoothing out the transition across the idle to hover throttle range. It does cut the power a bit but I am now wondering if by installing this restrictor I am masking some other problem with the engine such as a leaking crankshaft seal? I can think of no other reason that I cannot get a clean burning plug. The plug image is with the restrictor installed. Unfortunately, rain stopped play before I could try out the 90% restrictor. I also wonder if all this could be a result of having to use 92 octane unleaded gasoline.

Your thoughts on all this would, as ever, be much appreciated.

Paul.

[Tom Fiddler]

What is the deal on the restrictor?
This is the first I have heard of such a thing used in heli's

[bigrcr]

Paul,
I would not be too concerned about the center electrode being a light color, especially after only a flight or two. Make sure that the motor has no air leaks (as I think you have) and as I stated in another forum a while back, run the motor and get the needles right. Only check the plug if it is actually fouling (causing the motor to run poorly or not at all). Again, let the plug take the abuse, if any. Checking the plug too often will get you chasing the needles needlessly :roll: .

Concentrate on getting the motor running as smooth as possible with good strong transitions and fly it. If the motor does get a bit hot doing this, as long as it is adequately oiled, you will not really harm it. Just make sure that the air leak is gone!
Read the plug after about a gallon or possibly a half. This will give you a much better plug reading as the plug will have seen many heat/cool cycles and had time to get a build up (if any) and tell you what is going on. My plugs always look very much like yours with a fresh or light colored electrode insulator and a bit of black at the end of the threads and this is good.

This restrictor you are adding could very well be causing an air leak and could very well be causing you problems by this. The hole right near your restrictor is where the carb gets it's pulse from the motor to properly operate the carb. If there is a leak here the motor will either run poorly or not at all. The restriction may (if not leaking) be only causing you to change where the needles are set, not the actual mixture of the carb as the needles still will have their same function at a slightly different setting.

Don't worry too much about a clean burning plug! Just take a look after a certain interval to see what the motors oil ratio-air/fuel ratio is doing to the plug and just tune the carb for a happy motor.

Hope this helps!!

[FCM]

Thanks for your advice John. Sounds like I may be worrying about nothing. I'm an impatient sort of a person (I know, you guessed this already!) and I suppose I'm looking for 'instant' results which it sounds like I'm not going to get.

You are correct in thinking that the plug has not had much time run on it since it was cleaned. I only managed to fly for 33 minutes today so it was unreaslistic of me to expect a good coloured plug.

I hope to be able to get some more time on it tomorrow and I will remove the modified insulator block and refit the standard one. It did run nicer with the restrictor in today though - not that I ran it for very long.

Tom, the idea of the restrictor was mine I'm affraid. It was something I experimented with when I changed the gear ratio of my machine to 9.09:1 and fitted 810mm blades. I was initially unable to to get a smooth engine run due to the pretty dreadful throttle linkage which gave me very poor servo resolution preventing me from obtaining a steady hover speed with the then, unloaded engine + I was trying to run the head too fast.

I put the restrictor in to try and force the carby butterfly to be open more in the hover and it does achieve this after a fashion. I have only tried the 80% restrictor (I made up 70, 80 and 90% as you can see in the pic) as I then got to read an article in a mag. written by BillM which made me realise that a) I needed to ensure the engine was properly loaded, b) I should sort out my throttle linkage once and for all so that I could have a 'proper' servo throw and also enable me to run a GV1 and c) run the head slower!

The thinking behind it went something like 'if this engine was designed for 1/5th scale racing cars that rev up to 16000 + rpm with tuned pipes fitted, surely we (heli drivers) do not need as large an intake/carby as this'. All empirical experimenting of course, I'm not clever enough to know all the science (I know, that's obvious too)!

Best regards,

Paul.

[FCM]

This is the latest in my seemingly never ending oil saga that I thought I would share with you in the hope that somebody can make some sense of my findings.

Flying/testing was delayed due to personal commitments but this is roughly how things have turned out.

I could not get my engine to run without shaking using the Silkolene oil. Plug was also black with an overheated looking centre electrode.

I was fortunate to find some 'Ace Hardware' chainsaw mineral oil which sounded good as a breaking in oil so I ran 2 liters of this starting at 32:1 then 25:1 and finally 20:1 ratio. This oil burnt well but I had to keep increasing the oil content in order to achieve a smooth camera image. I did this in order to ensure the piston ring was bedded in properly.

I then stripped the engine and cleaned it and reassembled ready for running with my original Motul 510 semi-synthetic oil. I tried this today first at 25:1 then 20:1 ratios. The 20:1 gives the smoothest running with a just about perfect video image. Still got plenty of power and a nice smooth transition and on removing the plug after 37 mins of running - it actually had a nice light brown colour with no signs of lean running or overheating. The testing today was done in clear sunshine and it was hot so I do not expect any overheating problems to arrise.

All I can think of as an explanation for these problems is the fact that I have to run my engine lean in order to get a good video image. This fact has been mentioned before by BillM I think and I have to agree with what he said.

I also suspect that running a lot of oil lowers the octain rating (92 RON) of the petrol that I am forced to use which allows more complete combustion?

The Motul 510 oil is of much lower viscocity than either the Silkolene or the Motul 800 fully synthetic oils which I feel may have an effect on how the engine runs. Oil companies do not seem to quote viscocity numbers for their 2T oils so making a comparison is difficult.

Finally, as I have to run 'lean' with my engine, perhaps the high oil content cools the engine rather like what happens on a glow engine allowing me to lean that little bit more?

Sorry to have gone on like this but I really would like to hear peoples opinion and know if my theories have any validity.

Thanks,

Paul.

[FCM]

One week and no response? Anybody?

Thanks,

Paul.

[bigrcr]

FCM,
Sorry for the late response.
It seems like the Motul 510 at 20:1 is working for you. Each oil has the "best" ratio that it will operate at. Some have more impurities, more or less detergents, oils with different flash temperatures, etc. Some oils will stick a ring with a higher oil content. Some of the oils will actually glaze a plug in a lean condition. This is where the bead on the end of the electrode comes from as the oil cooks and crystallizes on the electrode.
If your plug after a few tanks is brownish without an oily residue, then it sounds OK. However, don't go changing the oil types after you settle on one. The motor will get "pickled" on one type of oil and when you switch, it has to set up different wear characteristics and some of the oils will actually be incompatible. When this happens, the previous film "pickling" can reject, if you will, the new oil making lubrication difficult and possibly hurt the motor.

Yes, it is possible to lean down the needles some with higher oil content and the added oil does in fact help to cool the motor. Sometimes more oil can make a motor run rougher and hotter (from increased compression), while other oils run at higher content can smooth out a motor.

This is one reason to run a highly recommended oil from someone with experience and pick one, then stick with it. Damage can be done to the motor in the long run by trying and changing oils. Playing with ratios using the same oil is OK as long as you approach from the rich side and lean down the oil a bit a a time and cautiously do it. Read the plug every 1/2 gallon (no sooner) or so to see how your oil and needle settings are.

But, somebody had to do some testing, so go for it. Just be cautious doing it.

Thanks for relaying your experiences as "it's all good"!

Keep in touch.

[FCM]

Hi John,

Thanks for responding. I will be sticking with the Motul 510 and will see how it goes over the medium/long term.

Yes, I did see some glazing when I was trying to run the Slkolene oil too lean I guess. The Motul 510 doesn't do that at least not at the ratio/mixture that I am running.

It's a bit crazy that I am back to using the Motul 510 after all the testing I did with 'high spec' fully synthetic oils - seems like I was doing it right in the first place but didn't realise it!

Anyway, thanks for everyone's help and advice - got to earn some money now!

Paul.

[FCM]

I thought that everyone who was following this thread should know that I am now running a completely different engine set up following lots of problems with using the Motul 510 oil at 20:1 ratio.

Although I could tune for a vibration free heli using M 510 at 20:1, it would not last long - not even a full tank before the dreaded 'shakes' would set it. I found myself leaning it out more and more which of course meant a hotter and hotter running engine. It was a vicious circle so I decided to lean the oil to 40:1 and also run the engine at approx. 11,000 RPM instead of 10,000.

This made a big difference and the engine was much happier running at this speed in our heat here in Malaysia.

I was still having problems getting rid of a slight roughness that was affecting the video image so I decided to bite the bullet and run a 50:1 ratio still with the M 510 semi-synthetic oil.

It didn't seem to make much difference and after about 4 liters of this I removed the engine due to suspected RF noise only to find the top main bearing was shot.

My rebuilt replacement engine is now running on Motul 800 (the really expensive fully synth. racing stuff!) at 50:1 ratio. I have followed the BillM's tuning procedure and now have it running rich but very smooth and cool at 11,000 RPM. Needles are L approx. 1 1/4 - 1 3/8. H 1 3/8. Carby is a 603.

The plug is a bit dark and oily but does not seem to foul so even though I probably could lean the oil some more, I will be leaving it as it is for now as it is working fine.

I do not know for sure why the top main bearing went on my old engine but it sure has been running hot and leaning the oil the way I did may have been the last straw. Of course the oil seal may also have been leaking and sucking air but I have no idea how you can tell if this has been happening.

Anyway the crankshaft has checked out okay so its just a bearing/seal change to get this engine back in order.

It's still early days yet with this set up but I am encouraged by the fact that I went out and flew today and didn't have to touch either the carby or the rotor RPM to maintain the good video image - the first time this has happened in a long, long while!

I hope that my experiences with the G230 RC may help somebody out there if only to show how not to do it!

Paul.

[bigrcr]

Thanks for the info! Seems you are on the right track for analyzing the motor and making the appropriate changes!

Later!

[FCM]

Last week I reduced the oil to 64:1 and today for the first time 75:1 ratio using the Motul 800 oil.

Plug is now cleaned up but still dark. Will be trying 80:1 mix after my next shoot :bomb:

Paul.

[FCM]

Flew an important shoot today. The engine decided to play 'rough' and I ended up leaning out the low needle to 1 + 1/8th before I got a semi- decent video image. This was still on Motul 800 @ 75:1 that had worked perfectly okay just last Thursday :? I + 1/8th seems too lean to me.

The plug looks dark and oily so I intend to lean the oil to 80:1 and test fly to see if this helps.

I may also re-install my GV1 to ensure that the correct RPM is maintained. I removed it in order to simplify the wiring/systems on what has become a quite complex machine.

Here's a couple of stills of my plug as removed today. You can just see the centre electrode showing 'lean' but with an oily black outer body colour. I may have allowed the RPM to drop off a bit as we didn't have time to tach. today. GV1 will sort this though.

What do you think John/Bill?

Regards,

Paul.

[bigrcr]

Paul,

I would be leary of leaning the oil ratio down much more. You may very well run into a lean oil/ lean mixture setting that will gall out the exhaust side of the piston. There may be a possibility that there are additives in the oil that may be burning and "ashing" in the combustion chamber. Take a look at the top of the piston and see if there are deposits starting to form. Your plug looks OK from your pictures, but it is hard to tell as the center electrode and insulator is not clear to see. I would not be too concerned about the black area on the body of the plug unless it is becoming a build up. You may try a hotter plug and the richen the needles a bit. What plug/gap are you using?