Lapping Inter head/barrel joint

Yes.. you should be able to remove with engine in frame.

The barrel should come off.  It's not as difficult a task as hinted by by George's instructions because you won't be re-shimming or assembling from non matching parts.

Removing and replacing the vertical shaft without displacing or changing the positions of the Oldham couplings needs care.  Especially replacing it.  But at least you don't have the Dommie pushrods to get back in place.

Having only one piston and a fairly generous lead in at the bottom of the barrel makes replacing it not nearly as awkward as with the Twins.  Watch out for the little oil feed tubes when you put the head back on.  Easy to miss them.

Barrel and clean head on the bench. The secret with lapping is to use very little pressure, a fine paste and keep moving the components 90 degrees at a time. Use the finest of the carborundum valve pastes, do not use a diamond paste.

Get the faces clean and use some engineer's blue to see where things are touching or not. Draw what you see. Add a trace of paste all round, try four 90 degree 'rotates', lift and move the head around 90 degrees, 'rotate', repeat two more times to get back to the start, clean it all up and do the blue test again. Does it look better? Repeat until you get clean blue lines on both components.

I have re-machined a head and barrel for a friend who lapped his 'to death' trying to make it seal. He had created seven thou of error in the joint, so beware!

I use fine grinding paste on the narrow joint and coarse paste on the wide (outer) joint. This makes it seal on the inner face, and the outer face stops it distorting.

John

If you are 2thou short on the spigot and you intend to end up with circa 2 thou clearance  on the flange. To pull down the sealing ring on the spigot you are reducing the height of the head barrel assembly by circa 5 thou.  This may diminish the tolerance in your Oldham couplings. After tightening up the head rebuild initially without the tube so you can confirm sufficient clearance. Be carful when tightening down the cambox , it needs to sit on each of the four posts and not sit up on an Oldham coupling.  J

Is there a good reason to lap the joint rather than simply add the gasket used by later ES2?  This sits on the broad face so the Oldham couplings will be that small distance further apart.

The spigot provides the seal for the combustion chamber not the flange. By pulling the head down onto the spigot it ensures a uniform load on the joint.  Trying to do that on the width of the flange mating surface would not give the same result.

Jon

ES2 gasket post war sits between the broad outer surfaces.  I believe it is alloy, but I don't know.  But it certainly seals on the broad flange.

….with  the consequential gap above the spigot? Wills ring??J

…each of your posts. Fit them and measure the finished height. Consider moving the posts to alternative (all) positions to get the best match. Once you have the data adjust the length of the posts to give you the tallest combined fit.  Identify the post to position (number stamp both)so that it’s clear which location the post will occupy. Then you may need to consider equal sized shims/spacers to get your stack height right.

Sounds like you have a good handle on what to do.

Enjoy, 

Jon

According to Franks: "A distance washer is fitted in the bottom of the cylinder-head nut recesses; care should be taken that none of these are lost".  They are certainly original.  The danger is of course that the feet of the cambox don't all sit down at the same time...disaster beckons!

The other curiosity is if the bottom rocker seal adjuster screws project too far down and contact the head before the cambox is in place....

Sounds like you know what you are up to, better than I.  There are earlier posts on this site about lapping the joint.  Not much about difference between alloy and iron engines.  Paul Norman's "racing vincent" site describes his engine rebuild in detail. His also had top seal adjusters.  They can be very close to the frame but if yours were there before you took it apart you'll know that.  He and (I think) George warn about possibly damaging the cambox legs if they don't bear down equally.  Possibly that's likely  to happen if the head has distorted and been ground flat.  Check with thin feeler gauges that there's no gap under any one foot when the other three are in contact.

Were fitted on one of my machines, a Stu Rogers mod as I remember. If you feel they are beyond use make sure you get wipers with the canvas core not just rubber.

The slight complication with this type of motor is the lack of a splined connection between top and bottom bevel.  ( The one nice feature of the Moore version and latter day Manx). Keep this in mind when you assemble from the crankcase up.

Enjoy it!

I used Wellseal but of course I don't know what would have happened if I hadn't used it.  It doesn't leak enough to notice.

Removal and replacement of head and barrel isn't anywhere near as much of a task as rebuilding.  You don't have shims to worry about, nor rebuilding the cambox.  The awkward task is relocating the Oldham couplings.  But that's easier than replacing with Dominator push rods.

Regarding the gap from 1st to 2nd.  Thanks to Barry's advice I bought the Daytona first gear kick start set from RGM and the bike is now much more usable in traffic.

Hi Bruce,

    What might be the problem with your engine is the ball bearing not seating or the spring is too weak or broken. These will allow excessive oil flow through the valve, first to the barrel and then the cambox. The factory service guide states the ball should be re-seated by giving the ball a sharp tap using a hammer and drift to reform the softer aluminium. You should fit a new spring as the original will be 70+ years old. The feed to the cambox should be around 8 psi, so you will need an oil pressure gauge to set this. It is best to use a clean dry gasket with a thin coat of non-hardening sealer on all 4 faces.

   When grinding the head/barrel joint you should use fine paste on the spigot and coarse paste on the outer joint in a concurrent operation. What this does is to make a fractional gap on the outer face to make sure the spigot joint closes first. Use sealer direct on all the contact areas.

Hi Bruce,

   Your conclusions sound correct, but you should dispence with the fibre washer as the lock nut should be hard up against the casting as the washer takes away the locking action. The number of turns out will not be a definite as the pump might be worn or you could be using a thinner oil or possibly some other variable. The cylinder feed only needs half a turn out unless you are using a forged aluminium piston. 

   Using an Inter on the road in the area where I live is a pain, pulling away from traffic lights up a 1 in 10 incline ( of which there are many ) is never good for the clutch. Second gear is good for 75mph which is breaking the speed limit, and third and fourth are so close you can forget which you are using. You might find it an easier ride to fit the ES2 cluster but using the Inter first gear as this will be almost the same as the early AMC gearbox and will improve your 0 to 60mph time which is safer getting onto a busy road.