Round 6, FOAK: 1982 Kawie KZ550 C3 LTD Restoration Options Options - Page 2

 


Oh yeah - I was annoyed when I saw the flaking then had to think about
when the lining had been applied... can't grumble at more than 10 years,
especially when I saw how rusty the outside of the tank had got.

The lesson I'll draw from that is that although the inside doesn't rust
once it's lined you can't guarantee the underside isn't rusting. I'll
just need to remember to pull this tank off come summer & de-rust the
underside. Or swap it for the NOS GN tank on the shelf.

Come to think of it, I've unscrewed the tank badges but they are still
stuck fast to the tank. I suspect there isn't much structural integrity
under the badges.

Not bad for 14 years as year round commuting wheels followed by a
further 5 years as winter hack. Not sure I'm looking forward to pointing
out to herself that she's owned that bike more than half her life.


I was going to get the Laverda tank lined as they are notorious for
rusting out the front corners but the tank is so vast it would need a
couple of kits and I dread to think what that would weigh.
--
Bob Scott

 


Notorious weak spot on a lot of tanks, that. Water trickles down
behind the badges and gets trapped. The Kawa GT550/750 fours suffered
from it. I used to take the badges off mine every year ot two, and
dollop a load of grease beind them. Never had a problem.

 


Bad form and all that, but something occurred to me just now - I think
this was the first time we had put the bike away with an empty tank.
Wonder if sitting with a tank full of petrol might have prevented the
peeling?
--
Bob Scott

 



Maybe. You have to consider the effects of long term exposure to
alcohol upon epoxy.

You can build an airframe from fiberglass or carbon fiber, but if you
want to
carry gasoline inside an integral composite tank in the wing or
fuselage, you have to use epoxy to bond the fibers together, because
alcohol will gradually eat up the traditional polyester resin that's
been used since the 1930's.

Volatile alcohol additives are the first fraction to self-distill out
of stored gasoline.

But, if the tank is empty, rust will start finding its way through the
epoxy tank liner.

Did you know that the pressure vessel of the Apollo command module was
all
epoxied together to make a very strong, lightweight structure?

We had to go to extreme degreasing of the surfaces and then abrading
them with Scotch Brite abrasive pads to get the epoxies to stick to
the parts that we were bonding together.

We had to prepare a test specimen with every joint we bonded together
and it was pulled apart on a tensile strength tested to prove its
strength.

Of course you cannot get inside of a motorcycle gas tank to abrade it
evenly, unless you want to sandblast it inside.

So the Kreem kit gives you some acid to etch the inside of the tank,
and how long you allow the acid to work and how you neutralize the
acid and dry the tank out will determine how much oxidization starts
on the inner surfaces before you get around to pouring the liquid
epoxy into the tank...