As it is a recent purchase, I don't know it very well.
At least I was able to find today a customer service manual, but in German, which I understand quite well.
I succeeded in replacing the belt this evening following the manual. I also found that the previous owner did not mount the deck straight (the left forearm was not in the same hole as the right one) and I think that did not help.
By the way, the mower deck is now running much more evenly than before.
So I would say my immediate problem is solved.
But I still would appreciate very much an English (or French, let's dream) issue of the customer service manual, because I'm still better in English as in German.
Owners manuals are a free download from Honda Power Products.
From the same site you can buy the service manual .
Mos are about $ 40 a small investemnt for a mower that will last a lifetime because it is so well designed and made.