Enya Super Sport SS40 2 stroke engine

The highly popular Enya SS40 two stroke model engine. I've a few of these in my collection, and have a high regard for them.
There's a variety of models in the Enya SS range, including different displacements, bearings, piston types etc. , this page details a plain bearing, plain piston version, model number 6301 ( as seen on crankcase back ), from my collection.

This engine was bought second hand, so a strip down and inspection was in order. This page details how I went about the process. The Super Sport is fairly typical of most model engine two strokes, so much of this would apply to many other engines.

Where required parts were lightly marked for correct reassembly later, the advent of the digital camera is useful here allowing quick recording of assemblies before pulling them apart.

This is the engine after being stripped, cleaned and reassembled.

Firstly the carburettor was removed, this entailing the removal of two crosshead screws. These are often tight little blighters, and being crosshead can already be butchered, thankfully they were good on this example and not excessively tight.
Next up was the front bearing housing still with the crankshaft and propdriver attached. This is attached with four cap heads and was easy to remove, but I damaged the fragile gasket. The cylinder head was next, this being fastened down with six cap heads ( the head screws have a different thread to the front housing screws so cannot be mixed up, which is good ).

Next job was the removal of the liner/piston/conrod assembly. The liner's position in the crankcase was very lightly marked at this point to enable correct assembly later. The liner on this example was a little tight in the crankcase to just pull out, so the whole assembly was heated up in a domestic grill for a couple of minutes or three, ( expanding the alloy crankcase away from the liner ). The liner was now easily removed by pushing gently up on the conrod with a gloved finger. The piston/conrod then being pulled downwards from the removed liner. On some engines after heating I grab the top of the liner with a three jaw chuck (lightly), some gentle pulling and twisting often get's the liner to oblige my intentions.

The gudgeon pin on these engines is secured by a couple of wire clips either side of the piston, these were removed with small pliers. Here it was noticed the conrod was not moving freely on the pin due to old congealed oil almost glueing the parts together. To remove the pin the oil residue needed softening up, so the grill was once again pressed into service to reduce the old oil's grip, which worked very nicely.
Attention was now turned to the front housing assembly. The prop driver came off from it's taper extremely easy which is always helpful, this cone is part of the crankshaft and not a separate part. Lastly the crankshaft was slid out and I had the pile of parts as pictured below.

Above are the main engine components. Not including the pin clips or the front housing gasket.

Below are the carburettor parts. Not completely stripped down, but as much as needed for cleaning. Disassembly of this carb was a simple job.


Carb is a simple air-bleed screw type.







The crankshaft on this engine runs in a cast-in bronze bush, excellent crankshaft to bush fit on this example.
The piston is cast iron running in a hardened steel liner, again excellent fit. Conrod is bushed both ends and is not on this example drilled or slotted for lubrication, fit here again is fine, so it hasn't suffered for it.
The cylinder head has a bronze bush fitted for the glow plug, a feature which reduces the chance of a stripped thread.

A careful inspection of the parts reveals a little used engine in fine condition, minimal play in all areas and an excellent piston/liner fit, should be a little cracker!

While I had the engine in pieces I though why not weight these components! Here's the approx weights in grams of the major parts.

• Crankcase: 80g
• Crankshaft 58g
• Front housing 36g
• Cylinder head 21g
• Liner 29g
• Piston 13g
• Conrod 5g
• Pin 2g
• Prop driver 5g
• Standard silencer 78g

Note the scales I used only have 1g resolution so the small item weights are very approximate!

Reassembling the Enya SS40

A fairly straightforward and quick process on this simple well made two stroke

Reassembly will be easy for any engine bloke (or blokess), so skip this if you like!
A new gasket was aquired ( borrowed from another dissassembled Enya SS40 engine ), and some air compressor oil poured into an empty squeezy oil can, plenty being used at all assembly stages. This stuff is my favourite for engine reassembly, I also use it in copious amounts when I lay up an engine.

Firstly the crankshaft was slid into the front housing casting, the prop driver slid on and the prop nut and washer fitted. This assembly was then laid to one side.
Next the conrod and pin were attached to the piston, with the front/rear marks I made on the conrod being used for correct alignment. The piston itself had some staining which matched the ports, this making front rear alignment easy without additional marking. The two wire pin retaining clips were then fitted with a small pair of pliers. These fit into a groove and must be fully seated or you will likely trash the engine when you run it. A little fiddly but not too bad, I myself prefer end pads instead of wire clips.

This combined piston/pin/rod assembly was then inserted into the liner from the bottom with respect to correct alignment. This whole lot was then slid down into the crankcase whilst getting the lightly scribed marks on top of the liner lined up. The liner slid in nicely with the engine now being all shiney and clean.

Cylinder head was next, this was fitted the same way round it came off, the six screws being gradually tightened in the usual cross manner, care being taken for square head seating.

Now the front housing assembly, together with the replacement gasket, was fitted to the crankcase whilst aligning the big-end to the crankpin. The four allen head front housing screws were now lightly nipped up.
The engine was checked for free and smooth rotation and the front housing screws tightened crosswise.
Nearly done already now, just the carb to be reassembled & fitted to the engine, and we're ready for a test run.

To be continued......( running and stuff )