"crush" washer or expandable aluminum?

[RDG]

Question? Do the fill "caps" on our Airheads use crush washers, or are they simply thick aluminum washers? I don't see anything "crushable" about these washers. I can understand wave washers and split washers, but not the simple flat aluminum washers provided in the drain kits. Everyone goes on about replacing these crush washers at every fluid change. A true crush washer would be that large copper ring at the bottom of the fork tubes, isn't it?

Seems to me aluminum expands with heat more readily than the metal caps, which would provide a tight push against the cap, holding it firmly in place with the expansion. I have gone years without replacing these washers. I simply clean the cap, threads, and washers, and snug everything up to a nice tightness. Knock on my wooden head, but nothing has come loose in all my riding in all kinds of conditions and roads. Is it plain dumb luck? Or do the aluminum washers do what they're designed to do-expand and seal?

[John Falconer]

The issue with re-use relates to their softness and the fact that if the two surfaces that first compressed them left irregularities in the aluminum washer's surface then, if it doesn't line up just as it had in the first compression, you'll not have as good a seal.

I prefer copper myself, but that's become pricey and not used as oftern (I think largely because of cost). Copper can be annealed between uses and even re-formed if necessary.

If you are caught having to reuse the aluminum washers, then it can be useful to inspect them carefully and, if they show signs of raised ridges, you can dress them flat on some emerycloth on a flat surface, clean them off, and re-use.

[barryh]

Aluminium can be annealed too, it's just a lttle more difficult to do without melting the washer. A smear of soap or washing up liquid on the washer will turn black when the correct temperature is reached.

[John Falconer]

Yep - correct, but much fussier. Copper is wonderfully forgiving in this regard.

A key step in all British bike engine top-end repairs in the '60s was the annealing of the copper head gasket - a nice (expensive) part to be re-used (less important then perhaps, but since I'm itching to tear into my back-to-me-after-a-long-absence 1966 T120TT Triumph, a welcome re-usability given today's high cost of copper).

[mattcfish]

Has anybody used the copper head gaskets that San Jose BMW sells? Remarks?
http://www.sjbmw.com/parts.asp#s=store& ... =1&pid=996

[John Falconer]

I haven't used theirs but wouldn't be surprised to learn that they source them from the same place I did purchase a set from. I had a particular need for a specific thickness at the time and used them until I could finish matching up a preferred set of parts and machining.

They work ... but they also leave the motor with less oil-tightness - they don't dribble, but they ooze; and this after carefully anealing and using the Copper-Kote like recommended sealing goop.

So ... my personal opinion - stick with the stock head gaskets and get the clearances you really need/want by proper machining.

[Duane Ausherman]

The original crush washers actually "crushed" and didnt' stay nice looking. I don't know when they got changed. On our own personal bikes, we reused the crushed copper washers with nary a problem. On customers bikes, we always replaced them due to liability.

I think that these new washers that don't crush are worthless as crush washers. I have no idea what they do that is useful.

[Deleted User 287]

I buy my crushable copper washers from Hucky's, but even his "kit" comes with two aluminum solids. The small ones for the driveshaft, I think.



I'd be just as happy to buy them from Matt. (hello?)

[Flatwins]

Thanks for the tip! The aluminum washer has always been a sore spot for me, especially on the final drive. I'm gonna try some of the copper ones.

[Frog]

I was surprised to read this thread, as I have been using aluminum crush washers for years....and crushing them.

I sometimes re-use them, if I run out of a given size.

They don't leak, and definitely are crushed and deformed upon removal.

I had a handful of used ones at my desk...so snapped a few photos to share.

http://picasaweb.google.com/blaisedesco ... directlink

These were all flat before I installed them. No stripped plugs. The surfaces are beat up, because they have been tossed around on this key ring for a few years.