On Oct. 21, 2003 there was a post on alt.honda that said, in part:

"I have a Honda EM5000SX generator I paid $2100
for new 5 years ago. It only has about 10 hours on
it as it's just backup for home. The other day it
gave no output and turns out some mice got inside
and ruined the generator portion. The Honda dealer
where I bought it said it would cost more to replace
the brushes and other components than to just buy a
new generator. . ."

Here's some more quotes on mice damage:

Nov. 21, 1999
" I recently finished rebuilding a (fixing mouse damage)
Honda EFs-5500 generator. . ."

Sep. 24, 1998
"I will need to fab up a metal box to keep the mice out
of the windings. . ."

Jul 30, 2006
"Mice in my shed have eaten away all insulation
from the inside of my EU3000is. Seems the
generator is noticeably louder without the insulation.
I can not find a dealer who can order these two
insulation 'blocks' from Honda. Can someone
please measure both insulation 'blocks' and post
the dimensions? I will try to glue alternative
insulation in its place."

I recently took a box cutter and made a small box cardboard box (out of
a larger one) and put it over my Honda Generator. Then inside the box I
put a can with holes in it filled with naphthalene moth balls.

Now, one problem that I have is those moth balls really smell bad. In
fact, they are stinking up my entire garage. That's a relatively small
problem, though. A bigger potential problem I am wonder about is
whether the fumes from the moth balls might damage the generator. Given
the potency of the gas that those moth balls (napthalene), another
problem, of course, is whether there is a health risk.

Here's an excerpt from something I found on the internet:

"CANCER HAZARD
Naphthalene may be a CARCINOGEN in humans since it has been show to
cause nasal and lung cancer in animals. Many scientists believe there
is no safe level of exposure to a carcinogen."

So, mothballs might not be a great idea, unless you can completely seal
the container. Even so, the question still exists in regard to the
generator. Is napthalene safe for a generator?

Does anyone have any other ideas on how to protect a generator from
mice?