bob36

My Feedback: (3)

I have aquirred two old diesel engines made by electronic developments co. Surrey england. One is a mark iv hunter 3.46 cc as marked on the box, the other is marked as a a mark II both are in the orginial box .
the mark II has the orginial instructions with it but is missing the rear mounted fuel tank. Both are frozen up with dried fuel.
Are these engines worth messing with? And would like to know their value,I cannot post pictures at this time will try later
thanks for looking.


Bob36

gossie

My word they are worth messing with. Both wonderful old engines from the '40s and or '50s.

Does the MK2 have a slot on the head to vary the compression ratio? If yes, it is in fact a MK2. Metal tanks as original are available. Is it only the tank missing or the whole carby unit that screws into the rear? Pics would help a lot.

Put them into a WARM oven to melt the old castor oil, DO NOT try to turn them over as they are as you may damage them......i.e. break the con. rod. When warm oil them and gently turn them over. Clean them up with a soaking in acetone for a week and a good scrub with a tooth brush.

Value? What someone is happy to pay...........But not a fortune.

Jim Thomerson

On the Hunter, the crank is supported by a ball bearing at the rear, and the crankcase acting as a bushing at the front. The crank is hollow and has two holes drilled through to lubricate the bushing. I was careless in cleaning mine up, and did not get the crank lube system clear. Result was galling and seizure of the crank on the front bearing. I got it cleaned up and relapped OK.

My references are out in the shop. I thought the MK 11 was front intake.

controlliner

Another thing to note is the rear disk rotor. It is die cast aluminum and the rear mating surface will eventually gall against the back plate. 33% castor in the fuel may eliminate this.

ffkiwi

Both are good engines-for their era-and purpose. What do you propose to do with them? They won't be setting any new records in C/L speed...! These days the only practical use for them is in vintage models-the 3.46 Hunter being quite competitive in SAM events. Re Jim's comment-the Mk2 is a sideport, the Mk3 was front indiction-both had rear tanks. If the 'Mk2' is a genuine one it will have exhaust stacks and a movable cylinder head (cooling fins) with a slot in the top-the entire component screwed up or down to adjust compression. If it has a normal 'T' shaped compression screw it is the later 'Competition Special' model-produced in very large numbers from 1948 right through till ca 1961. The 'Mk2' on the casting is a bit of a red herring, as though the original was indeed called the 'Mk2', ED continued to use the front housing-with its 'Mk 11' marking cast in, on the Competition Special-as well as a very short lived MkIII of 2.5cc capacity-of the same sideport layout-which they then dropped in favour of the front induction MkIII. .....but they then were left with quite a supply of front housings-complete with Mk111 cast in for the 249 sideport that they were now not making... Being sensible-and frugal-they simply ground off the extra '1'-and used these housing in the Comp Special. Even today you can find examples of the Comp Spl with the 'Mk111' housing ground off to 'Mk11'-the grinding mark is obvious.

Anyway-back to the matter in hand-the 3.46 is quite a potent motor-but ported for medium revs-so best used on something like a 10x4 at around 10,000rpm, the Mk11 (which is 2cc capacity) produces less than half the power of a 3.46, but will happliy turn a 11'' or 12'' prop at 5,000-6,000 rpm (much like a vintage spark ignition engine-and a lot quieter!)

Obviously to get them operating, you'll have to unstick them-and this is best done with heat-in a warn oven for 15 or 20 minutes-which will soften the hardened castor gum-then pull them out (wearing a glove obviously!) put a decent sized prop on them, tighten the prop and try and get the engine to turn over-which it should start do-albeit sluggishly if you've got it hot enough-then hit it with CRC 5-56 or WD40-in the various orifices-intake, exhaust port and behind the prop driver, and keep moving it till it frees up further, then squirt a bit of after run oil in and keep the process going. If the engine won't budge after a decent heat soak treatment-it would normally suggest that something is broken or jammed internally. If you can turn it over bottom dead centre after it is freed up, but not over top dead centre, then this normally indicates that the compression has been wound down too far, and the contrapiston is too far down in the bore to allow the piston to travel over TDC. You can feel this easily in a freed up engine (there is a mechanical blocked feel when you try and turn the engine over-and you can usually hear the piston making contact with the underside of the contra)-in an old engine with perhaps a lot of residual castor gum in the upper cylinder, this may not be quite so obvious......
The answer is to back off (unscrew) the compression screw (or the head if it really is a Mk11 'penny slot') half to one turn and try again. If you're lucky (and the engine is still hot enough from the oven) the contra will move back to the new lower setting, and you should now be able to turn the engine over. A lot will depend on what the state of play was when the engine was last run-if it was rich, and not run dry, there could well be a lot of old fuel residue inside, and freeing up will take time-if it was run properly and wiped down, then there won't be much, and the heat treatment should free it up easily. [I have a little bench top oven-the sort you use for heating pies and snacks-I use for freeing up such jammed motors-I normally set it at about half max, and the timer for 20-30 minutes-a normal domestic oven works fine as well-but perhaps you might not like a castor oil flavour to the next sunday roast...]

Value? Impossible to say with any degree of accuracy-it will depend on the condition of the engines. Neither are rare-ED were by far the largest UK manufacturer of their era, and probably produced something in the vicinity of a million engines (for example they made over 300,000 examples of the 1cc ED Bee over its Mk1 and Mk2 versions-and they manufactured at least 12 different engines over their history). Keep an eye on Ebay-EDs come up quite often-and this will give you an indicative relative value (depending on the condition of yours relative to those being sold on Ebay)

A couple of points to note-the EDs naturally will use British threads-BA, BSW and BSF-so bear this in mind if you are going to replace any screws-both (if complete) should have spinners rather than prop nuts, but if any of these these are missing then you'll need to source suitable replacements-which are not hard to find in the UK, but likely to be thin on the ground in the US!

Here's a shot of my examples-including a rare factory glow 3.46-plus a side by side shot of a genuine Mk2 (without stacks) beside a Comp Spl-the heads are different but the big giveaway is the deeper exhaust ports on the Comp Spl. It was not uncommon though, for people who owned a Mk2 to retrofit it with a Comp Spl head, and use a normal comp screw, rather than the original setup-likewise the crankcases were a bit fragile-especially in the mounting lugs, so were easily damaged in a crash, and often replaced by the 'incorrect' model.. Likewise-tanks-which could be aluminium (mk2) or plastic (Comp Spl) were often removed or swapped around-the Comp Spl tanks could be clear, amber or red-and as a rule haven't lasted well-being prone to split and warp over time. The tank thread is 1/4 BSF should you need one or decide to have one made-I made my own on the restored example on the right-from Delrin which is a very good material for the purpose.

ChrisM
'ffkiwi'

bob36

My Feedback: (3)

Thanks for your quick replys guys, I just took another look at the EDs the ED marked MII is really a MIII the carb parts are still on both of the engines how ever the fuel tank is missing on the hunter. As I can no longer fly rc due to a serious health problem {heart}
I started in rc in 1967 and I miss the hobby very much but i can not do anything that is physical for more than a few minutes, so I will probably put the the engines up for sale along with a O&R 19 that is in the same condition as the EDs.
Thanks again for your help guys.

Bob36

ffkiwi

Err-the Hunter doesn't have a tank....you just used the appropriate sized tank for the type of model you were flying, just like most modern motors.The Hunter was also known as the ED 'Mk4'.... Incidentally the Hunter survived into the modern era and was still available in the early 1980s-but looked a lot different to the ones pictured here-though the crankcase was still fairly similar to the original layout.
A quick summary-in case there's still some confusion:

ED Mk1 1cc, rear disc induction, monobloc crankcase with slip in liner, two exhaust ports either side at the rear known coloquially as the 'ED Bee' Introduced 1949
ED Mk2 2cc, sideport induction, metal fuel tank, short crankcase, 'stovepipe cylinder' with all moving head for compression adjustment, usually found with angle exhaust stacks Introduced 1947
ED Comp Spl 2cc sideport induction, development of Mk2, no exhaust stacks, deep exhaust ports, conventional T-shaped comp screw Introduced 1948
ED Mk3 2.5cc, Short crankcase, stovepipe cylinder, scalloped head fins, front induction, with separate rear overhung tank. also available as glowplug Introduced 1948
ED Mk4 3.46cc rear disc induction with cam turned cylinder, finned head, two exhaust ports on right side, long shaft with extended length prop driver Introduced 1949

So you can see that 'Mk number' as far as ED were concerned referred to engine size, and these were not introduced in numerical order. Just to complicate matters, ED's most famous engine-the ED 2.46 'Racer' (as it is known to everyone who uses or owns one) was officially called (by ED) the 'ED MkIII series 2'.....despite having nothing in common with the earlier Mk111 other than a similar size...
To further complicate matters, users and collectors use the words 'Mk' or 'series' more or less interchangably when referring to different models of the same ED engine-and in a different sense to ED, so you have the ED Bee Mk1 (which itself had several minor variants over the period 1949-1956) the ED Bee Mk2 (1955-1963-again with minor variants), the ED Mk4 Hunter with at least 5 submarks or series) and the ED 2.46 Racer with at least 6....

Those familiar with EDs know what we mean with these distinctions-but it can be quite confusing for those who don't-and even then we are not entirely consistent-the last production model of the ED Racer, introduced in 1969-is quite a bit different than the preceding ones-and to EDs was known as the 'Super Racer' but to others simply the 'ED Racer Mk6' or 'series 6' [though internally it was no different from the earlier production models]

ChrisM
'ffkiwi'

gossie

I'm still trying to work out if one of the ED engines is in fact a MK2?

Does it look like in Chris's photo?.........The engine on the far left? The second one from the left with T shaped compression screw is a Competition Special..........Both are 2cc in capacity.

If it is a MK2, I may be interested in it as that model was my first engine in the late '40s. I do have a Comp. Special and a MK2 would be nice to have to go with it and to use in a Free Flight model. PM me if you prefer, and a picture of it would be most helpful please.

bob36

My Feedback: (3)

Err your right the hunter does not have a tank. And you are right again it is quite confusing.

Bob36

gossie

FWIW here's my Comp. Special in a Frankenstein Free Flight model.

beatsal

What is the best way of cleaning with acetone i.e. pouring it into the exhaust ports or soaking

ffkiwi

Acetone is not a particularly good choice for cleaning in any case-it usually (in commercial grades at least) contains quite a lot of water. The best approach to cleaning old dirty or gummed up engines is to start with heat-put the offending article in an oven- say about 120C for about 20-30 mins-removing any plastic parts beforehand-once too hot to hold, grab it using an oven glove, put a prop on it and carefully rock it back and forth over about 45 degrees of movement, increasing the movement as it frees up until you can turn it over compression a full rotation,. Then squirt a bit of oil into the opening and keep turning over. whilst still hot, loosen any screws-head, backplate, front housing which may have been locked solid by old hardened oil, and then do a partial dismantle-that generally being removing at least the cylinder head and backplate. At that point you can generally put the item in a bath of solvent to soak-lacquer thinners or MEK being quite good.

Simply soaking an assembled motor in acetone-even for a week-may not achieve anything useful-it is not a particularly aggressive solvent-especially where dried or gummed castor oil is concerned, and if the piston is at TDC, blocking the exhaust port, and the intake shaft port closed off there is nowhere for the acetone to get inside, and start softening and dissolving any residues. It is however a fairly safe solvent--which is why it is often used for nail polish removal-but there are better choices when it comes to cleaning engines...

ChrisM
'ffkiwi'

beatsal

Thanks Chris. Mine is a 3.46 MK IV. If I remove the cyl head and backplate not sure if any gaskets to contend with

ffkiwi

There shouldn't be...ED prided themselves on finely machined metal to metal joints....that being said with a lot of the older ones-MkIIs, Comp Spls, and the 3 46-I reckon gaskets are not a bad thing....and this bloke:

https://www.ebay.com/sch/the-old-eng....m47492.l71970

....does a nice range of gaskets-including a lot for the ED range (not all but most of the range)

Depending on the age of your 3.46 you might or might not find it has a loose big end bushing....a bit like the first Veco 19.....personally I never quite saw the point of a loosely fitted big end bush-seems like to wear both on the ID and the OD in use. I would not expect to find a gasket between the cylinder and head...unless its a factory glow (yes-they do exist-I have one...)-but it's not uncommon to find one-usually homemade between the backplate and case or between the cylinder flange and the case. Many EDs have passed through multiple owners in their life, some of whom may have been harder on the engines than they deserved-and perhaps damage or distortion occurred to those originally nicely machined metal to metal mating surfaces...necessitating fitting a gasket to ensure a good seal....

ChrisM
'ffkiwi'

beatsal

Thanks. Looks like a good way to start the engine would be heating and then putting on a prop and trying to rotate. Any idea what would be the best size prop to use to try to start i.e. I saw 8X4 mentioned - is that the best or would a 10X5 or othe be better

ffkiwi

Sorry we are talking two different things here-one is freeing up an old engine gummed up with hardened oil and old fuel residue-starting such an engine is entirely a different matter. Focus on cleaning it up, internally or external, before entertaining ideas of starting it. Have you ever handled a model diesel before? If the answer is no then you definitely need the assistance of an experienced modeller who has had actual 'hands on' experience starting and running diesels-make sure you establish that fact before inviting him to have a go-there are plenty of modellers with LOTs of experience-but if they haven't handled diesels-then that experience-even if its decades worth-counts for nothing in this situation. Trust me on this! Experience with glow engines is not directly applicable to diesels-the latter have their own quirks and idiosyncrasies. They are not hard to start-providing you know what you're doing-but that is not necessarily intuitive to someone who hasn't done it before. The 3.46 is not a difficult engine to start-but it is a large diesel-and it will punish inept handling fairly brutally-as will all large diesels. Getting whacked by a 10 inch prop on a backfire WILL make you sit up and take notice, believe me! Flood the engine, hydraulic lock it and do something stupid like use an electric starter-and you will be looking at a broken crankshaft , bent rod, broken gudgeon or all three. Assuming the engine was put away after the last time it was run and hasn't been fiddled with since-there's a good chance the compression setting will still be in the correct running setting-so within cooey of the starting setting-though you might have to back it off by half a turn initially. Your expert assistant will be able to determine this.

If you do have diesel handling experience then ignore the preceding paragraph-jump to the next one and take note of the appropriate prop recommendations. If you don't have much experience then I suggest going slightly larger -to say 11 inch diameter will making starting a bit easier....a 3.5 can be a bit intimidating if your past experience was limited to a Mills 75 or DC Merlin. In its day the 3.46 was a popular choice for R/C models (which of course were valve radio back then-and weighed a lot-so the models were large and fairly heavy), also popular in B team race-before the .29 glows started to dominate-and in recent times-become quite popular in the US for some of their vintage classes-to the extent that CS even made a replica .19 sized version just for the US market.

In any case you will need suitable fuel-which is in fairly short supply in the UK at present (where I assume you are-please correct me if I'm wrong), a suitable prop -see below, and a good solid mount. The 3.46 is not especially fussy about the fuel blend-any decent commercial diesel fuel will do

I don't know where you saw mention of an 8x4-but forget it-that would be appropriate for the 1cc ED Bee! The 3.46 Hunter is a relatively low revving (for its type) slogger-and peaks around 10,000rpm. A 10x4 is a perfect match for peak revs-or if you had CL in mind a 9x6.....in the unlikely event you felt compelled to fly it in vintage team race-then an 8x8 might be appropriate. For vintage R/C perhaps a 10x5-but if you want to chug around gently it will have no trouble hanging on to an 11x4, 11x5 or even larger diameter for something like a lightly loaded slow flying vintage model. Its a big heavy motor, and produces just over 1/4 HP. Engine test reviews can be found here: ED 3.46 Mk IV
and here: ED 3.46 Mk IV (2) -being the 'Model Aircraft' and 'Aeromodeller' reviews respectively. Note that both these are of the earliest version-the tall cylinder variant-I am not aware of any published test data on the later shortened cylinder version (of the Mk IV)...there is a MUCH later version called the Super Hunter-but that only appeared in the 70s and 80s and whilst sharing some ancestry with the original, is a quite different engine...

ChrisM
'ffkiwi'

beatsal

Thanks Chris. No, I have no experience either freeing or starting a diesel. Eventually I do hope to start and run this engine. I tried to contact people in the know about diesels but no luck most are good on small gas engines. I am based in Toronto, Canada. The top compression screw seems free - only tight when I tighten it down fully to the end. Not sure what that indicates.

ffkiwi

there are Canadians who post here-so it may pay to trawl back through the threads and PM them and see if any are close. Fuel is going to be a problem-I doubt any commercial fuel is available in Canada-judging by this and other forums, so you will have to make your own-unless you happen to know a friendly high school teacher or university chemistry department employee, your chances of laying your hands on ether-[and specifically diethyl ether-not any other type of 'ether'-of which there are dozens of different types, cyclic, acyclic, crown etc ]an essential ingredient of the fuel is extremely low-as it is a fairly tightly controlled substance in most jurisdictions...even down here in NZ. however there is an out-especially in Canada...John Deere 'cold engine start' sold for starting dificult to start full size auto, tractor and stationery engines in cold weather contains a high proportion of diethyl ether-around 80% and you can use this stuff when formulating your own fuel to provide the necessary ether. Typically model diesel fuel contains diethyl ether, kerosene, and lubricating oil=plus a very low proportion of ignition smoother -by very low I'm talking 1-2% by volume. The lubricant can be mineral oil, castor oil, or one of the synthetics used in glowplug model engines-though I hesitate to recommend the latter for use in diesels-unless it is one of the blended products that contains a reasonable proportion of castor oil in it-around 20% by volume Klotz Super Techniplate is an example of what you might rightly call a 'fortified' synthetic. Klotz 'Benol' is an example of a modified improved castor oil.

Typical proportions for ,model diesel fuel would be: oil 20-25% (higher for plain bearing engines, lower for ball bearing)-20% should be considered a minimum level. traditionally fuel used to be 1/3-1/3-1/3 of the aforementioned ingredients and 1% amyl nitrate as the ignition smoother. That was 'way back then' and while it works its a bit generous in the lubricant quantity-most of which goes through the engine and ends up on the model! Its saving grace was that it does no harm-and its very easy to measure and mix.

Ether-and it is solely there to provide the ignition of the fuel charge ranges from 30% up to about 45% (the latter being recommended in very small diesels...and by very small we're talking 0.5cc or smaller capacity)-it is also the most expensive ingredient (these days) so if you can get away with 30% then there's no need to go higher.

Kerosene is what your model diesel actually burns to produce power-so that is the remaining component-and the more kerosene in the mix, the more power the fuel can produce. Note there is NOTHING in diesel fuel that parallels the use of nitromethane in glow engine fuels-there is no magic constituent you can add more of and get a sudden boost in power like you can by using high nitro fuels in a glowplug engine.

A lot depends on your actual engine and its usage-a racing diesel intended for high performance might use a fuel contain 20% lube, 30% ether and 50% kerosene, with a dash of ignition improver somewhere around the 2% v/v mark That fuel will not work especially well in a plain bearing sport motor-which will be happier with 25% lube, 35% ether and 40% kero-(and maybe 1-1.5% ignition improver if your feeling generous). If the engine is worn-then you will have little choice but use a higher % of lubricant in the fuel to ensure easy starting and running....remember-the piston cylinder seal is everything in these diesels-as that's how the heat of compression fires the charge...with poor or low compression-you're on a hiding to nothing. Its no accident that worn diesels are often pigs to start....yet ironically once running, often run well...the reason is simple-the poor compression makes generating enough heat of compression at cranking speeds difficult-so in trun the engine is reluctant to fire-but once running the heat of combustion helps keep things going-and the worn piston cylinder fit means less friction, so they often run quite well-but will usually be impossible to start again until they've cooled down......when they'll be merely difficult...!

There is every liklihood that your Hunter has been run in the past on a castor based fuel-and that is one of the reasons I don't recommend using a synthetic oil in the lubricant-these oils have a detergent action and may well strip the castor layer from the inside of your engine-resulting in poorer piston seal and compression (it does happen-engines run on castor based fuels will acquire with time (especially when properly run in) a thin layer burnt onto the piston surface and cylinder walls-which generally improves the seal-and removing it-either by deliberate cleaning or running synthetic-can often result in disappointment.

Now the screw in the top adjust the position of the contra piston-which is a very tight fit in the cylinder-it has to be otherwise combustion pressures will force it back up, compression will reduce, and the engine will misfire and eventually stop. The fits for the contra are about 10 times more critical than the piston fit itself-which needs to be fitted to an accuracy of about 0.1-10.2 ten thousanths of an inch-in contrast the contra has to be made to about +/- a 50,000th -to get a unit that will move under the force of the compression screw, but hold its position under combustion pressures...and you often find them either too tight, or too loose a fit. too loose can be dealt with by a lock on the compression screw, too tight is always problematic. The compression screw on your Hunter should be turned clockwise until you feel it touch the top of the contra piston. You will feel the difference between the screw moving through empty air inside the head cavity, and the sudden resistance when it contacts the top of the contra piston. Don't turn it any further as that will push the contra further down into the cylinder and lose your settings-and you definitely don't want that, as a raw beginner. When starting, or adjusting a running diesel it may be necessary to increase or reduce compression-depending on the prop load, the fuel being used and how wet the engine is-you reduce compression by turning the screw anticlockwise- half or a full turn. Inside there is now a gap between the top of the contra piston and the end of the compression screw-and in a well fitted engine, the contra will jump up this distance-either from running pressures, or the compression of being flicked over-this is normally discernible by a sharp 'click' as the contra moves up and makes contact with the end of the compression screw.

The point to all this talk about compression setting-is that this determines the TIMING-the engine will fire at slightly different points in the cycle depending on the compression-higher revs and smaller loads require the 'ignition' timing to be advanced-and that is what the compression adjustment does-it advances or retards the ignition point depending on where it is set-just like a classical model spark ignition engine-and just like one of these-you normally retard the ignition point for easy starting..in a diesel that means reducing compression by 1/2-1 turn...especially with a cold start [its not absolute-some engines need the compression increased slightly when starting from cold-and then reduced slightly as the engine warms up to running temperature-which may take about 30 seconds or so of running] Now most engines you'll find will probably have a range of only about 1 full turn on the compression screw for the full range of normal prop sizes likely to be used-from largest to smallest-so providing the compression is somewhere near the running setting on yours it will not be too difficult to find the right settings for any particular prop and fuel. [this is largely a result of most diesels having either 2BA,(UK) 5 or 6mm (Europe) or 1/4-28 thread compression screws-so the pitch is roughly the same-now and then you'll find an oddball that uses something different-and the 'approx one full turn of adjustment' rule may not hold. Fortunately your ED 3.46 uses the traditional 2BA thread....

What style of head is fitted to your 3.46? The early ones had a head with fins on top-like many glow engines-the later ones had a plain unfinned head.....both were retained with 6 screws-but the unfinned ones could be plain alloy or in some cases anodised a lime green colour These plain heads all seem to be associated with the change to a shorter cylinder (along with a shorter conrod) in the mid 1950s.

ChrisM
'ffkiwi'

Coxfledgling

Sorry to hear of your ailment...

All good info above...

Spectrefilght is a good info source too.

I use ( UK based ) ordinary car petrol which seems to shift most caster gum.

Remember a diesel, or a better description, city, compression ignition, will have a high compression ratio, so do not force over tdc untill the engine is really freed off.

A strip and clean would be good but reassembling so the piston and liberr are in exactly the same position, can be difficult.

Not seeing the engines, I would just submerge in sufficient petrol in a suitable jar, agitate often and leave soak for a day or two.

You will see the globules of caster appear in the liquid. The liquid can be filtered for reuse until spent.

Remember petrol is a very real fire risk, so do this stuff outside.

Take your time and enjoy...

I avoid 3 in 1 oil and wd40 for this application.

You have some model diesel engine fuel ?

ffkiwi

OK beatsal-to give you a bit of inspiration please check out the following Youtube videos:
These will show you a) that they start easily b) the effects of adjusting the compression and c) the size of props they can turn.

[I recommend doing a search on 'Brian Cox' videos on YouTube -he has numerous videos on bench running a variety of classic (generally British) model diesels-and as a beginner you can learn a lot from simply watching and listening to the commentary]

ChrisM
'ffkiwi'

aspeed

You have some great guidance here. In Toronto, you may want to phone AJ Hobbies. Jack would know a bit or at least give a few ideas for where to get ether or find someone who knows.

beatsal

Thanks, will try this i.e. "submerge in sufficient petrol in a suitable jar" with the top compression adust screw removed?
Yes, have fuel, mixed 1/3 Castor, 1/3 kerosene and 1/3 ether.

beatsal

I have the ether, got it from J Deere as someone posted. Still trying to free the piston which does move but does not turn over.

ffkiwi

Don't worry about removing the compression screw-that will not achieve much-as the area above the contra piston and the underside of the head is unlikely to have much congealed oil in there-and having the comp screw out will not do anything towards freeing up the engine-the cylinder is sealed at the top by the contra piston-and you should never-under normal circumstances-try and remove it.

Rather than soak I would recommend you do what most of us use-and that is heat. First obtain a suitable prop-if you don't already have one-and I've already given you suitable sizes. Ensure you can fit this to the engine and tighten it up-the prop driver has a recess into which the spinner nut shank fits when screwed home on the prop. The spinner shank is 9.5mm diameter-so your propeller will need a through hole of this diameter-which may well be larger than the hole in the propeller as you buy it-so may need to be enlarged. This needs to be done carefully-with a suitable piloted reamer (which you are unlikely to have) or even more carefully with a pillar drill. Don't attempt it using a hand drill-you'll mess it up. The safest way is to start with a drill just too large to fit whatever the existing size hole in the prop is-then enlarge it to the final size in a series of ascending size steps till you reach 9.5mm. Fit it, ensure you can tighten it up tightly, using a tommy bar thru the spinner cross hole (an suitable size allen key works...)-then TAKE IT OFF again.

NOW you're ready to get on with the job! Put the engine in a domestic oven at about 120C for 20-30 minutes. Take it out-you'll need an oven glove obviously-fit the propeller, tighten it up, and now try and turn the engine over by twisting the propeller back and forth through about 45 degrees of motion. If its just normal gum and congealed oil that had it stuck, the heat will have softened the oil and gum so that you should achieve some movement. If it won't move at all-give it a bit more time in the oven (take the prop off first) then repeat the process.

Once you get some movement, drop some oil-a few drops-into the air intake and onto the exhaust ports and keep increasing the movement arc of the prop-once you get the piston below the top edge of the exhaust ports-a few more drops of oil into the cylinder and keep going. You should-under most circumstances now be able to turn the engine through a complete revolution-though it may still feel quite stiff. While its still hot, try and loosen the four backplate screws-and if you can, remove the backplate and intake assembly (as a single unit-there's no need to take the intake and needle valve assembly off)-do this again by twisting back and forth to break any oil seal gumming the surfaces, NOW you can put it into petrol to soak-as removing the backplate will allow solvent to access the lower interior-and if the piston is at BDC, the cylinder interior is also accessible. There is normally no need to dismantle any further.

An old toothbrush and /or a small bottle brush is useful for scrubbing out lumps and flakes of debris from the inside. When cleaned to your satisfaction, reassemble-ensuring you get the crankpin extension (the bit that projects beyond the conrod big end)-into the drive hole in the rear disc. Oil it again as the petrol will have washed out most if not all the lube you added earlier. ...and now you can contemplate making up some kind of suitable mounting prior to attempting your first start.

Don't be tempted to clamp it in a vice-this is a sure fire way of ruining the engine-mount it correctly to wooden bearers using bolts through the mounting lugs-and four bolts-no half measures. The reason why a vice is an absolute no no-is that you have to grip it so tightly to prevent movement-and your're gripping the crankcase by the lugs-squeezing them together in the vice jaws-that the crankcase will distort-and that's the end of it-there's no going back from that. The videos I posted earlier show a variety of suitable mounting methods.The simplest is simply a U-shaped cutout in a piece of wood at least 1/2" thick, just wide enough for the crankcase to fit-ie 1-1/4" wide and at least 2-1/4" long. Easily done by hand with a fretsaw-and even more easily with a Dremel saw if you have one..

To make life simple-as you saw in one of the videos-1/3-1/3-1/3 fuel works OK in the Hunter...which makes it easy to mix up. don't forget-the John Deere product is not 100% ether, its about 80% so you'll have to factor that aspect into your mixing volumes. Luckily experience has shown that the remaining 20% content can be treated as if it was kerosene-it isn't but it is similar hydrocarbons which will burn OK in the fuel.

ChrisM
'ffkiwi'

beatsal

Thanks. Just to clarify:
Enlarge the prop hole by drilling with a bit one size up till it eventually fits?
A toothbrush may not fit inside the cylinder for cleaning.
Is the a connection between piston and contra-piston?