It is much easier to remove or replace the engine in the frame without the cylinder head , it also helps to remove the lower part of the rear mudguard . However BE VERY AWARE that when you have removed all the obvious cylinder head nuts , two more lurk at the back of the head INSIDE the inspection cover below the distributor . Failure to appreciate this fact is the reason why so many Sunbeams have broken fins on the head or barrel .
Having got the engine out , dismantling is straightforward except for the plug at the front of the crankshaft sealing the centifrugal sludge trap , and you MUST get it out as it is amazing the amount of hard packed crud that lurks therein .
There are four possible ways of doing this :--- Firstly you can try using a screw driver as described in the " Bedside Book " , you may get lucky but I doubt it .
Secondly get it machined out by a COMPETENT machinist , if done correctly the actual thread can be pulled out like a spring .
Thirdly have a short piece of hexagon bar welded to the plug which gives you something to heave on .
Lastly the real backwoods way , drill a 3/8" hole through the plug and then open it out with a square file till a socket set extension bar can be banged in .
Having got the plug out and cleaned up the threads , get a new plug made up to the full depth with the outer 1/3rd machined to a hexagon , so that you can screw it in ( and out ) with a socket wrench . Using Loctite Medium Strength or Thread Sealant to make sure it stays put .
OIL LEAKS
It has been said that you cannot stop a Sunbeam from leaking oil , this is not true but you do have to work at it a bit .The most common places for leaks are :--- the head joint around the oil feed drilling and cam chain tunnel , the rocker cover , and the distributor , the original oil pressure switch can also cause problems .
To stop the oil feed leak the only effective method is to bridge the across the head gasket with a piece of tubing .
After checking that the drilling in the head is concentric with the hole in the gasket , the head should be drilled and reamed half inch deep by 10 mm diameter and a piece of tubing one inch long pressed into place , the 10mm diameter is normally a snug fit in the gasket .
Now for the tricky bit , the drilling in the barrel does not usually line up with the gasket and is drilled on an angle which makes life difficult . The method I use is to put the head in place without the gasket and give it a good thump with a hide hammer thus marking the barrel , then I start carefully grinding out with a small rotary file . Alternately thumping and grinding until the head fits metal to metal , care should be taken to get as good a fit round the tube as possible , finally lightly countersink the hole .
When installing the head put a light smear of silicone sealant ( Plastic Gasket ) on both sides of the head gasket round the cam chain tunnel and rather more around the feed tube , the idea being that as the head is bolted down the silicone will be forced inwards around the tube and form an in situ " O " ring . I suppose that with a bit of cunning and the right size countersink one could install a proper " O " ring but it would need to be a high temperature one .
The problem with the rocker cover joint is that the cover itself is not strong enough to clamp down properly onto the thick gasket , which is why you find so many covers that have been damaged by over tightening .
So clean up the mating faces , drill the three nuts for a locking wire and throw away the gasket . Install the cover with a smear of silicone on both faces and on the shoulders and threads of the nuts , tighten the nuts down enough to make a seal but not enough to damage the cover , then wire the nuts together for peace of mind ..
To prevent leakage round the distributor install an " O " ring round the mounting spigot ( see the section on ignition ).
If you really really are having trouble sealing the oil pressure switch , drill and tap the head 1/4 BSPT and use one off a car , I use a Ford Cortina Mk 3 but there must be many others that would do .
LUBRICATION AND BREATHER.
A Sunbeam engine as it comes suffers from too much oil in the crankshaft area , while at the same time having a shortage of oil around the camshaft . When the engine is at rest the oil drains through to the sump with no problem , however once it is started , due to the presence of the flat plate supporting the oil strainer combined with the windage of the large internal flywheel most of the oil soon finishes up above the plate going round and round with crankshaft . This explains why a Sunbeam needs two oil rings per piston and in some a small drop in oil level will set the oil pressure light flickering . The following three modifications done together will solve these various problems :--
Firstly the centre hole in the support plate should be covered by a riveted on disc , then a row of four holes of the same size should be cut along the left hand side of the plate as shown below . These holes will allow the rotation of the crank to return the oil to the sump with much greater efficiency . ( For a further development of this modification see " Full flow oil filters " ) .
Secondly the original breather must be blanked off , as any serious attempt at increasing the camshaft oil supply will result in a flood down the front of the engine . This is easily done by clamping a thin plate under the outer breather cover where the slotted plate normally goes .
The only place for the new breather that really works is out of the oil filler cap there being just enough room , clear of the retaining spring , to drill and tap 1/8 BSPT for a suitable brass fitting . A 5/16 bore flexible tube should be swept up under the spark plug cover then down past the front snubber and back along the frame to end near the rear suspension ( see the gallery ) . I know of at least six bikes in the club which use this system successfully and all I have ever had out of mine is drops of condensation .
Finally we come to the camshaft , this mod is a bit more radical as it involves turning or grinding a groove ( about 3/16 half round ) completely round the camshaft rear bearing boss in line with the oil feed hole. This will give a full pressure feed to all the camshaft and rocker bearings but more importantly will enable the sequential camshaft oil spray to work properly as each rocker lifts , provided the holes in the bushes line up .
Running the engine with the cover removed is a bit like watching a cow being milked as a jet of oil comes out from each rocker in turn , whilst the slotted plate does a surprisingly good job of keeping excess oil away from the valve guides . It is very comforting to know that as soon as the oil pressure light goes out , the camshaft is being properly sprayed as in any other self respecting OHC engine .
