Advice on Four Strokes for Newbie

[Nigel R]

Enya are good motors, but less common, and I think spares may be an issue.

 

Os and saito are far more common.

 

You pays your money etc. 

Edited April 7 by Nigel R

[Andy-H]

Thanks again. As regards fuel, Jon suggested above using fuel with 5% nitro & 15% fully synthetic oil content. Is this a stock off the shelf product or would it need to be specially ordered ? I called SMC with a general enquiry and they suggested Duraglow 5% or 10% but that seems to have 6% castor oil content which I’m keen to avoid.

[Nigel R]

Model Technics Laser 5 - is 5% nitro 15% synthetic

 

[David Davis]

...and it's obtainable from Model Shop Leeds and most other good model shops. https://www.modelshopleeds.co.uk/catalog/product_info.php?cPath=291_1011&products_id=79264

[Andy-H]

👍

[Nick Cripps]

DD's link was for Formula Irvine Sport 5 fuel.

 

This is the one you want.

[Andy-H]

Thanks all - understood.

[Paul De Tourtoulon]

Here we go again,,,😨

 100 pages on fuel,,,,🤢

 

Most fuels are good, a good all around mix for ALL 4 strokes especially the older ones is 10% nitro and 15% oil including in that a bit of caster.

[Outrunner]

Don't for

13 minutes ago, Paul De Tourtoulon said:

Here we go again,,,😨

 100 pages on fuel,,,,🤢

 

Most fuels are good, a good all around mix for ALL 4 strokes especially the older ones is 10% nitro and 15% oil including in that a bit of caster.

 

Don't forget the caster as without it your engine won't gum up properly 🤣

[Paul De Tourtoulon]

57 minutes ago, Outrunner said:

Don't for

 

Don't forget the caster as without it your engine won't gum up properly 🤣

Yes, but without it, I will be going back to change the bearings on my 4 strokes every 2 years. 😡

[Jon H]

1 hour ago, Paul De Tourtoulon said:

Yes, but without it, I will be going back to change the bearings on my 4 strokes every 2 years.

 

Then you are doing something wrong. I have never had a set of bearings go that quickly even in my especially vulnerable os FF240. Its 6 years into its set of bearings i think and its still fine. I use no castor, no after run... 

[Engine Doctor]

2 hours ago, Paul De Tourtoulon said:

Yes, but without it, I will be going back to change the bearings on my 4 strokes every 2 years. 😡

Every two years ? Really. I ran a Saito 45 for five years on one set and a ys 63 for longer with no bproblems . All my fuel is synthetic based , never use castor except in old engines and diesels with iron pistons / liners. 

Edited April 8 by Engine Doctor

[Paul De Tourtoulon]

My saito's have been running for around 30 years, and only needing piston rings ( 3 x .45s and 1 x .45 std ) all run with at least 2% castor, I ran My Enya .90 and 120 on synthetic only fuel and they both needed replacement bearings in a very short time.

 

 Don't forget that I live in the south of France and fly mostly ever other day,,,

[Paul De Tourtoulon]

34 minutes ago, Jon H said:

Its 6 years into its set of bearings i think and its still fine

6 years means nothing, How many hours of running ?.

[Jon H]

1 hour ago, Paul De Tourtoulon said:

6 years means nothing, How many hours of running ?.

 

hours mean nothing. model engine bearings almost never wear out, its always rust. In fact an engine run often will easy out last one that is run infrequently. 

[Andy-H]

Me again. Can I ask what folk do for replacement gaskets if a four stroke motor needs striping & cleaning ? I’m assuming old gaskets are likely to tear during disassembly. Are spares available or is there a DIY way of making new ones ? 
 

Also, I’ve seen reference to using a low-oil fuel with Laser engines. Does that mean Laser engines are less messy than other brands or am I misinterpreting this ?

[Paul De Tourtoulon]

Don't get hysterical about fuel, oil, and cleaning oil off of an engine with a 150 bar pressure washer.

All engines are oily, it what modelling is all about.

A rag and alcohol for cleaning oil from methanol engines, I make my paper joints mainly from paper from envelopes and cardboard ones from paper cardboard foldes, it is quicker than looking for them on the internet.

[Bruce Collinson]

Suitable later Lasers will run very successfully on Laser low-oil fuel with significantly less exhaust mess.   I believe no other common 4 strokes are safe on it due to differing construction and materials.   Slightly more powerful too as there’s proportionally more methanol.

 

Jon might well dive in with dates when he reads this.

BTC

[Frank Skilbeck]

1 hour ago, Bruce Collinson said:

Slightly more powerful too as there’s proportionally more methanol.

 

 

Might be miniscule the fuel mixture has to be adjusted to get the correct fuel/air ratio for a good burn, the oil is a negligible volume

[Bruce Collinson]

1 hour ago, Frank Skilbeck said:

Might be miniscule the fuel mixture has to be adjusted to get the correct fuel/air ratio for a good burn, the oil is a negligible volume

Tesco.

[David Davis]

Andy-H it would help if you could tell us which engine you are talking about.

[Jon H]

3 hours ago, Andy-H said:

Also, I’ve seen reference to using a low-oil fuel with Laser engines. Does that mean Laser engines are less messy than other brands or am I misinterpreting this ?

 

Time for a little history. 

 

In the dim and distant past before they invented colour, bean juice (castor oil) was used in engines as a lubricant. Up to 30% was not uncommon for model engines in those days and castor was a very popular choice. 

 

This popularity was for good reasons. It was inexpensive, easy to get hold of, and did a good job as a lubricant. It was also quite viscous which could be an advantage if the fits within the engine were a little suspect as it gummed up the gaps. Crucially, it was better than synthetic oils of the day. Just ask the Germans in WWI. 

 

However, castor also makes a dreadful mess and leaves carbon/varnish all over the innards of your engine. The goo on the outside can also gum up cooling fins as dirt and bumble bees get suck to it, exhausts get blocked, and its prone to setting solid leaving your engine totally locked up. It is also a natural product and so its performance will always vary. As a result, you need more of it to guarantee the required lubrication. 

 

Fast forward to today and we have synthetic oils which are assembled molecule by molecule using computer controlled voodoo. Engines are made from vastly superior materials and with much tighter tolerances. Since the 90's 15% synthetic oil has been all you need and frankly even this is excessive with 10% probably a more realistic figure today. It always causes a row as not everyone has moved with the times but castor is a dead lubricant now and best forgotten. As they used to tell you at school, quality over quantity. 

 

When i was working at laser i did experiments with oil content. This was an offshoot from petrol engine work i was also doing. The petrol engine was running at 40:1 (2.5% i think that is?) at the time, so i wondered if a glow engine would work on that. I mixed up methanol and oil at the same ratio and left it running at 75% throttle for an hour, when it finally ran out of fuel. I then flew some of my own engines on 5% oil for a few years, this was no bother, and then introduced the low oil fuel at 7% to give a big improvement over standard 15% oil fuel, and give room for improvement later. 

 

Some customers have run their OS engines on the low oil fuel and had no problems, but i havent tested that so its on you if you have a go and it fails. Frankly, i think OS's would be fine, but as i dont fancy getting yelled at when someone kills their prized motor its not a recommendation from me, but 15% is fine for everything. 

 

If you stick to 15% oil, which you might as well do unless you have a laser, you can clean up your exhaust residue significantly by tuning the engine for peak performance and nut having it chuff around half a turn rich of peak and with a slow run needle set so the engine is on the verge of hydraulic lock. Always tune for peak performance on both needles. 

 

[Andy-H]

By way of context, I’m planning on buying a couple used motors to take apart, clean up and reassemble. Just to get a better idea of how they work. Hence asking about gaskets and thanks for the ideas, Paul. 
 

Then, I came across a thread elsewhere on this forum talking about Lasers using low oil fuel whist other makes needing a higher oil content, which caused me to wonder whether Lasers generated less oily exhaust residue, so many thanks Jon for your advice. 
 

I’ll probably look for a couple of engines that are either as new or lightly used to put to use in an airframe. No fixed ideas just yet, all depends on what comes up. 

 

[David Davis 2]

I may well try running my OS 52FS Surpass on the new low oil Laser fuel. If it goes off bang, I have a spares engine damaged in a crash which I could use for internal parts. It might give me an edge in La Coupe Des Barons! They're planning on having all of the four strokes compete in the same group this year, the sound of up to ten four strokes in the air at the same time could be very pleasant. However, I'll continue to run my old Lasers on 15% oil mix.

 

The new low oil fuel certainly generates less oil residue. I use it with a Laser 70 in an Acrowot and a Laser 80 in a large Kadet Senior ARTF clone.

 

 

[Paul De Tourtoulon]

Just to put some oil on the fire, where on earth is the dirty black gum, after ten years of it screaming around the sky, with 2/3% castor in the mix, I just can't find it.

 

As jon says, OS like most engines will run properly on 15% oil, any less won't make a noticeable power différance.