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Messing about with Mercos'

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jeff2wings19/08/2018 18:54:43
755 forum posts
1763 photos

Well Percy,that depends on the kind of spares you need ! If like every one else back in the day,you used castor fuel the engines will be in good condition under all the crud,however,50% of the 49&61's I've brought the bearings have been toast from the congealed castor.I have used Model fixings for replacement bearings for the Mercos and other engine projects,not the cheapest but they more often than not arrive the next day yes .Things like piston rings can be had from gaviscool on e-bay,and I make gaskets from thick brown parcel wrapping ,as for any thing else,I make !

Frank,as Percy says,however,that said,if it's a small case mk II from '66 on, the carb choke was smaller so suction would be fine,should make for a nice retro combination with the astro hog.Try and get a P&R strap on silencer,I may have one going spare in my box of bits !

SR71 ,the 29&35's come up on e-bay ,sometimes for little money you can of course convert an r/c to stunt by locking the throttle open or fit a stunt venturi.

some more pics of the 35imga0277.jpg



Percy Verance19/08/2018 21:16:24
7567 forum posts
145 photos

Well Jeff, I don't need any spares just now, but if I were to begin flying my Mercos once more then I probably might need spares at some point. The last spare I needed was a crankshaft for my .49, which got bent in the resulting crash following a mid-air in 1984.........and of course they were readily available back then.

Edited By Percy Verance on 19/08/2018 21:17:02

jeff2wings03/09/2018 22:20:05
755 forum posts
1763 photos

Just a few more finished engines....................




and this is one of my Ltd 'Black edition' 49 Mk 1 made from leftover bits !



next will be a Mk 111 and another bitza

jeff2wings11/09/2018 21:38:19
755 forum posts
1763 photos

Well this is the last of the Merco restorations ,I still have plenty of others to build/restore that will be in my other thread,I may even build a (retro)model or two for them! dont know


Mk III with micro-flow carb bit of a rarity (for a merco that is lol !)



MkII with Enya carb from the bits box

Frank Skilbeck11/09/2018 22:22:30
4310 forum posts
101 photos

Jeff, the Mk111 with micro-flow is what I've got. I tried running it but was getting a very severe leak from the cylinder head joint, took the head off and there is no gasket, so it looks like I will have to address that.

jeff2wings12/09/2018 07:28:46
755 forum posts
1763 photos

Frank,mercos never had head gaskets the head sits directly on the liner,I would suggest you try lapping them together,if that dose not work I will look in my spares box ,might have a twin plug ?

Frank Skilbeck12/09/2018 08:15:17
4310 forum posts
101 photos

Jeff, thanks, I will investigate further. The engine has been cleaned up by a previous owner so I will have a look at the head/cylinder joint to see if there is any problem there.

It looks like it has newish head screws, 3 short and 3 long, just wondering if these might be slightly too long and are bottoming out, do you know what length they should be.

ken anderson.12/09/2018 14:30:19
8349 forum posts
768 photos

hello Jeff,

I admire your work on the engines....well done

ken admiration dept.

jeff2wings12/09/2018 22:29:19
755 forum posts
1763 photos

Thanks Ken,it' a bit like restoring a car or motorcycle,but quicker and not so expensive (as I keep telling the wife!)

Frank,short screws are 3/8 long(threaded part) and are 1/8 whit ,have found the test report by Peter Chinn in the Sept '68 RM and no head gasket,however looking at the pictures it looks like the cylinder head has been machined to leave a band around the combustion chamber,my guess to size would be 1 1/8 o/d x.020-30 thou high .The head on my Mk III is also flat but I think at some point in the last 50 (!!) years it's been ' got at' as it had a non-Merco con rod in it so may not be the original head?

s-l1600 (8).jpg

as received,no gap at head

merco 61 mk iii page 1.jpg

you may just be able to see the raised band on the head

Edited By jeff2wings on 12/09/2018 22:31:10

jeff2wings13/09/2018 20:45:35
755 forum posts
1763 photos

So had a go at a spare head on the lathe


std head just visible witness mark from liner


30 thou step


smaller contact area will give better seal

jeff2wings16/09/2018 18:36:54
755 forum posts
1763 photos

So popped the head off my Mk III for closer inspection and it looks like the Mk III's heads are different to all other merco heads,there is a 10 thou step(not 30 like I made) the Mk II was a bit of a odd one out to previous and following engines.


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