Cylinder liner

[THEI]

Hi,
Now I got my RGS cylinder head out of machining shop. What is the optimal value of the cylinder liner sleeve (penetrating to the cylinder head groove) height or distance from sleeve to cylinder head?
Before machining the cap between sleeve and cylinder head was 0,3mm. After machining it will be smaller.
I do afraid that there may be metallic contact if the casket is thinner (or softer) as previous one.

 

[mauricejota7604]

How much did they take off the head .
You need to be very careful here the other thing you will need to know is what head gasket do you have.
There has been a recent issue involving incorrectly made head gaskets ,

 

[THEI]

Cylinder head was 0,15mm yielded, and now it is strait. I have no accurate information of depth of machining but I believe that it is about 0,15-0,2mm.
I wonder what is the purpose of the cylinder liner sleeve, because 1200cc engine does not have that sleeve at all (if I have understood right).

 

[CLEMTOG]

you do understand correctly the 1200 (80mm) does not have the spigot on top of the liner which protrudes through the head gasket and into the cylinder head on the 1000 (75mm)

It should not make contact with the head, that would prevent correct compression of the gasket, its purpose (I imagine) is to prevent gasket burn on the edge, this is controlled by the flame rings inset to the gaskets, but an extra shield can only be good, it might also soak a little more heat into the fins of the cylinders, who Knows?

There are several 1000's running around with no spigots and solid copper head gaskets (commissioned by me) with no ill effects. I could never understand how an accurate finish of the cylinder block top can be achieved when the liners removed, and then installed later, causing distortion as they are shrunk in, better to machine the cylinder top with the liners fitted, but impossible with the upstanding spigot. That joint face should not be done on a mill using a fly cutter, although that does happen and with good results, much better to take it down very gingerly with a surface grinder, the difficulty being the wheels need to be able to work and not clog when machining both aluminium and cast iron, clogging causes scratching and gouging, the local tool making shop bought in special wheels and coolant for me, in order to achieve this, did two jobs (spot on as well) then the business closed.
CLEM

 

[sfcpiet]

The purpose of the spigot lies within the design of the head itself and the head gasket.  It should also be noted that 1000 pistons have a greater compression height than 1200 pistons.  Dunno what there is to not understand...

The spigot indeed protects the gasket from taking the brunt of combustion pressure.  It should reach to within a few 1/10 mm of the roof of the combustion chamber.  It also fills in the ring-shaped void that could otherwise cause burn problems in regard to uneven heating of the chamber when using pistons of less than 80mm diameter.  And it helps to uphold the compression ratio.  The flanged edge of the liner should be 0.1-0.2mm lower than the gasket surface of the cylinder casting, if using the proper original gasket with the slightly thicker flame rings!  If only a gasket with uniform thickness is to hand, the liner flanges need to be flush with the sealing surface!  Over time, abuse and many, many heat cycles, the alloy of the casting actually shrinks, while the liners do not.  This leaves the liners proud of the actual sealing surface, creating all manner of problems.

Apparently, the factory deemed the gasket capable of dealing with the mean pressures created by the 1200s lowly 8:1 compression ratio, and the spigot was omitted.  The heads are identical!  This called for a shorter piston, as it only rises to the height of the sealing surface, instead of above on the 1000s.  The same regarding liner recession/protrusion holds here as well.

Due to the slight fuck-up by the gasket suppliers a couple of years ago, there is a huge stock of flat, uniform thickness gaskets.  These are very handy for 1200 barrels that have been skimmed flat to rectify liner protrusion, no need to pull the liners and adjust the liner flange to correct the recess.

Imho, a solid copper gasket can only be used sucessfully on a barrel with the liner flanges flush with the casting, any other condition will create similar problems to those of the "flat" gaskets.

All this has peviously been discussed at great length, I think there is a search button somewhere... :

piet