Cyl O-rings

[beemersanducs]

Getting ready to change pushrod tube seals, I notice the Clymer book shows O-rings on the studs and a large one that goes around the barrel and says on bikes so equiped.....how do I know if my 1973 R75 LWB has the O-rings? I know I could pull it apart to see but I would like to have all the parts ready to reassemble.

[vanzen]

Max-BMW's on-line cat site:
1973 R75/5, engine, cylinder, shows this diagram:


# 05, part # 11111255001, GASKET (to 08/75)
With a notation:
"Up to 08/1975 use 001 base gaskets and 11321250267 push rod seals.
We also recommend a sealant Hylomar, BMW part number 81229400339."

And for a later model
1978 R75/7, engine, cylinder, #05, part# 11111337567, O-RING - 93X2,2
Notation:
"... BMW added an extra o-ring groove in the cylinder foot in May of 1979.
If your (cast iron) cylinder does not have a groove for the big 11111337567 o-ring,
then this o-ring does not apply. These only apply to Nikasil cylinders.
Exception: there is a low octane metal base gasket specified for the 1976 R60/6 and 1977 R60/7
that will de-compress other 1976-on airheads,
but is generally not needed in the USA."

[beemersanducs]

Thank you

[chasbmw]

BMW no longer reccomend Hylomar as a sealant, it really does not seal very well and will leave an oil mist around the cylinder/ crankcase join.

The current reccomended sealant is Drei Bond, Not cheap but works well, available from Bins etc or sold as Yamabond/Honda bond etc etc

[vanzen]

BMW no longer reccomend Hylomar as a sealant, it really does not seal very well and will leave an oil mist around the cylinder/ crankcase join.

The current reccomended sealant is Drei Bond, Not cheap but works well, available from Bins etc or sold as Yamabond/Honda bond etc etc

To the best of my knowledge,
"Drei Bond", "Yama-bond" and "Hylomar" will each be brand names,
all of which describe a very similar (if actually a proprietary)
silicone based non-setting, sealing / gasketing compound.
Even as the buyer should be aware
that each company will offer several formulations of the product
and each will be suitable for certain applications ...
The operative term remains: "very similar".

"Hylomar Universal Blue was originally developed in the 1960's by Rolls-Royce Plc
to help seal against synthetic lubricants that were used in early jet engines."

[robert]

BMW no longer reccomend Hylomar as a sealant, it really does not seal very well and will leave an oil mist around the cylinder/ crankcase join.

The current reccomended sealant is Drei Bond, Not cheap but works well, available from Bins etc or sold as Yamabond/Honda bond etc etc

To the best of my knowledge,
"Drei Bond", "Yama-bond" and "Hylomar" will each be brand names,
all of which describe a very similar (if actually a proprietary)
silicone based non-setting, sealing / gasketing compound.
Even as the buyer should be aware
that each company will offer several formulations of the product
and each will be suitable for certain applications ...
The operative term remains: "very similar".

"Hylomar Universal Blue was originally developed in the 1960's by Rolls-Royce Plc
to help seal against synthetic lubricants that were used in early jet engines."

Cliff Cavin, is that you??---Norm

[chasbmw]

Hylomar is very different to the Drei/Yama etc etc Bonds. Hylomar is blue with a a fairly jelly type consistency, it used to be the recomended sealant and I used to use it, the Bond type sealants are grey in Colour with a paste like feel,

The difference in use is that Drei Bond will continue to seal after many miles and many torque /retorque the heads sequences and the cylinder base joint will remain dry.

This is my experience anyway.

Please remember the usual caveats regarding only using a smear of sealant and being very careful around the small O rings.

When the engine is back together and full of oil, you can easily check the oil flow to the rockers, by removing spark plugs, grounding them and turning the engine over on the starter with the valve covers removed.