Date: Sat, 21 Sep 1996 18:43:02 -0400
From: Mike Taglieri
In a message dated 96-09-20 10:07:10 EDT, you write:
>I retorque the [Commando] base flange more often than the head, cause
it
>leaks more. Easier than doing the head on a 750, too. But partly impossible
> on an 850.
>
>That eternal leak is one reason I dream of scratching up US$500 for
an
>aluminium cylinder. You just can't get a permanent leak free joint
between
>two pieces with such dissimilar heat expansion properties as iron
and
>aluminium.
There seems to be an easy way and a hard way to fix any problem, and I think buying an aluminium cylinder seems to be the hard way to stop a leak. You can get a reasonably permanent and leak free joint with dissimilar metals by using silicone instead of a base gasket, because it stays flexible enough to move a little. At one time, Norton itself began to recommend this, then retracted the recommendation because idiot owners were gooping on so much they were blocking the oil return drillways. Since that's the only problem it caused, DON'T do that, but use just a little smear of silicone on surfaces that are smooth and burr-free.
An aluminium cylinder, in contrast to the cast-iron one, is not a component that's been made by the thousands and refined over the years to get the bugs out. Therefore it could give you problems you hadn't even dreamed of, especially if they took the cast-iron design and did it over in aluminium without considering the difference in relative strength of these materials.
Mike Taglieri
Raul -- '72 Commando Interstate