I have a Honda HT4213. The engine sounded like there was something inside it and then stalled. Now I think the engine seized. It had oil in it, as I have to add oil every time I use it. I'm afraid it is toast! Can the engine be rebuilt?

Hi,
That is a very expensive engine to rebuild, not that it is not one of the finest engines ever built. It is a water-cooled inline twin. Somehow I have never seen a Honda engine failure that was not heat or oil related. They use some of the best heat-treating and alloying in any industry.
The information on service and parts are available at the European Honda website. Some info is no longer available because of the fact that not many were made. It never caught on because of the cost.
Peace,
Clarke

I agree with Clarke.
That engine is one of the best.
It would be cheaper to rebuild
Than buying a new one.
Luck