Four Stroke query

[Keith Garner]

I have recently obtained a new four stroke engine and have read all the horror stories about corrosion when the engine is not in use. Is it necessary to buy "After run oil" from the likes of "Just engines" or will any general purpose oil do, such as "3in1"?

[Evan Pimm 2]

The corrosion is due to the hygroscopic properties of the fuel (Methanol). It will happen in any engine that is rested for any length of time with fuel residue in the crankcase. The prevention is well known, at the end of each flying session remove the fuel supply with the engine hot, running at a fast idle and with the plug igniter attached. This will help to scavenge most of the remaining fuel. At home a few drops of Auto Trans oil or some other moisture dispersant oil (air tool oil, for example) flicked through to coat the insides, then hang the model nose up so that any crap will drain to the backplate where it can do little damage will see the bearings last long enough to require replacement due to wear, rather than corrosion.
Evan.

[the unmagnificent man]

Hi Keith, after every flying session I drain the tank then start the motor again until it cuts out due to lack of fuel. After that I squirt WD40 down the carb and turn over the engine about 5 or 6 times with my thunb over the carb. As Evan says this coates the inside with water dispersing oil. It works a treat. If I am not going flying for a while I remove the plug and place oil directly in the cylinder as well as down the carb. Al

[Tim Mackey]

I always use 2 stroke motor mower oil - red stuff, cheap and looks /smells identical to the "proper" after run stuff that model shops sell.
Automatic transmission lube is also good, as is airtools lube.
SOME people reckon that WD40 should not be used, as it has tendency to harden out after a while, but personally I see no problem with using it, after all, it is hardly likely to be in the engine for long enough to "dry hard", and it is after a water dispelling fluid- thats where the name came from after it was developed Water Dispellant formula 40 was its design name....

[Keith Garner]

Many thanks for all the helpful information.
Keith

[Bladerunner]

Hi Keith.
Even if you run your 4S engine dry you may still suffer from corrosion. You should also note that specific to four-strokes the crankcase contains some corrosive by-products of the combustion process, not just unburnt methanol. The crank-case lubrication system (for bearings, big-end, cams etc) is fed from piston blow-by, and finally exits the crank-case via the breather vent.
There are many folks that squirt additional fresh oil into the breather to inhibit corrosion and this can be done via the silicon tubing that is normally attached to vent oil from the cowl area.

Also, using fuel with a bit of Castor oil goes a long way to preventing corrosion in four-strokes. There are many synthetic/Castor blends on the market containing 3% - 6% Castor that do the job nicely.

Enjoy your engine.

[Tim Mackey]

Thats good advice Bladerunner. I always used to squirt a little oil in the crankbreather nipple too, until the manufacturers decided that this venting would be better fed back into the inlet manifold, for better scavenging I preume, either that or the greenpeace lobby have been at work again. Now, because of the orientation of the engines, cowling, and the fact that the connecting tube is all within the cowl, it is nigh on impossible to access ANYWHERE to get after-run oil into. I have resorted to injecting a few squirts into the exhaust, and flipping the engine over - glow plug OFF of course guys :-) to try and suck a bit back into the insides. Must confess though I tend to use totally synthetic lubes in all my IC engines these days.

[Myron Beaumont]

Timbo
I thought you were all 'lectric !

Have found a use for my fly cam thing-
The plastic it was hermetically sealed in will make a lovely canopy IF 'er indoors will lend me her hair drier .
GM

[Myron Beaumont]

PS
If you put WD 40 in be careful flicking it over .It can fire up apparently
GM

[Tim Mackey]

MOSTLY electric Myron, mostly,...but still love the sound of a nice 4T in my Spitfire :-)
Also still have a couple of trainer type thingies which Mrs T was learning on, and will be resuming as and when she is well enough again.
I actually still feel that a good IC airplane is more practical for beginners for several reasons, as illustrated in the thread I did over in "beginners begin here". I did stress GLO PLUG OFF when turning over the after-run oil :-)

[Myron Beaumont]

Timbo
I actually was referring to the glow not being attached with WD40 in the internals. Compression only !

[Tim Mackey]

I doubt the average model 4T engine would start and run with no glow, surely the compression is not high enough ? Crikey, most beginners have a hard enough time getting them to start and run WITH a glow attached LOL
These sort of theories abound in this and many other hobbies, but is there any real evidence of this happening? Has anyone actually ever witnessed / performed a running non glowing model 4T engine on WD40?

[Myron Beaumont]

Timbo

I'm only repeating what I've read on a thread or in a mag  I don't believe for one minute it would run but that there could be the chance of a "kick" Try it & see !

Have a doctor standing by  'cos you're probably not used  to using a finger ,only switches & a fire extinguisher standing by   LOL Myron   only being out of of order again

 Grumpy M

PS   now my lines are further apart on this M/C !!!!!!!!!

[Tim Mackey]

I have flicked many a 2 and 4T in my years Mr Beaumont

Yeh I guess there is a chance of a kick, but then my missus still does the lottery, depsite me constantly stating the odds ! 

[Mark Lubbock]

I'm not sure if this is true but I remember seeing somewhere that WD type oils should not be used in glow engines-something to do with the silicones saturating the plug & destroying the catalytic reaction of the platinum filament with the methanol. Incidentally, I have an old Enya .09 which will happily fire up without the glow being attached (Enya no3 plug/Southern Modelcraft 5%)when spun on a starter!-I found this out when drawing fuel through & it surprised me so much I had to do it a few more times to prove it! I suspect tolerances have led to a higher compression ratio than normal, coupled with the catalytic reaction mentioned earlier, giving enough heat to start. In all other aspects the engine behaves normally, in fact it's the best Enya .09 I have ever used.

[Martin McIntosh]

YS engines specifically tell you not to use after run oil because if it is petroleum based it will destroy the silicone seals within the motor, also not to run out the remaining fuel, simply store the model with the cylinder head facing downwards (which I always do, of course???), But what I always do is to ensure that the fuel line to the carb is completely drained so that it does not become clogged with thick oil. I have not as yet had any such corrosion problems with any of my four strokes as far as I know, but plenty with OS two strokes. May be that the hotter running four strokers burn off more of the corrosive substances Don`t know. MM.

[Gerry Stansfield]

 Is it feasable to convert a glow engine to run on petr/oil mix. without it over heating. I have an enya 90 4c, I would  like it to run on petrol but I don't want seize it, I have a spare walbro carb if I can make an adaptor to fit it, also I have an electronic ignition unit I could use. any suggestions?.

[The real Ron Truth]

I was always told NEVER to use WD40 on engines as its so damaging to seals, gaskets and greased bearings. Hence why its banned in Commercial aaircraft servicing.

 If you leave you engine for weeks un run, use a few drops of after run or cheap old 3 in 1.

If you run your engines every week, dont bother. It is good to run the engine dry, drain excess fuel and leave the model nose up to let any nasty liquids rest away from the front bearings. Lots of after run makes the engine a bugger to start.

[David Turner]

I use cheap cooking oil (sunflower) from the supermarket and flood the engine' cavities after a day's flying. Costs nothing and does no harm to the silicon bits of my YS. If the internal spaces are flooded, all air is excluded and there can be no corrosion.

JE after-run is petroleum-based and will do for your silicon bits.

[Allan Jordan]

 Evening all, I have never tried to start a glow engine using WD40, I can however assure

 you that a diesel can be made to run using it as fuel! my advice to you all is don't risk the stuff as after run lube. auto trans. fluid is by far the safer bet. Allan J..TTFN