I am stuck (for a couple of days now) so I went to look at Stella's walkthrough and that's something I don't like to do.

http://tombraiders.net/stella/walks/TR8walk/12xibalba.html

I am at the bottom of that walkthrough using the calendar puzzle to open something in the big area below, then get there on the motorcycle before it closes?

Well, I get there and I don't see anything.

What am I supposed to be looking for?

There isn't enough time to get there even on the motorcycle!

Also in the walkthrough it says 1st and 2nd calendar puzzle.

there are 2 of them?

I only did one after putting the skull (that I found in that deep pit Lara broke through by using the grapple hook to pull down a stove) on the lever and turning the 2 levers to align the symbols.

There are two puzzles - one with a skull and one with a jaguar head. Have a look at the map in the walkthrough - you need to pick up the jaguar head near where you entered the level.

The calendar puzzle for it is opposite the skull calendar puzzle.

Also have the motorcycle parked at the hole in the wall. where you turn the second calendar. There is ample time to get to the court, you'll hear music playing, you have until the music ends. Another thing is to keep an eye on the map you see on the screen. You'll come to an intersection, the court is not far from the second calendar, turn left when you see that intersection and you will be there

I had the motorcycle parked right at the hole before I did the puzzle.

I also saved the game again after I completed the puzzle.

Then every time I load my saved game, the motorcycle gone and it wants me to do the puzzle again.

I give up.

There is no passing this level.

Putting the motorcycle in place and saving the game before doing the puzzle doesn't do any good because if you don't make it and you load the saved game to restart, the motorcycle disappears.

Saving the game after completing the puzzle doesn't do any good either - reloading the saved game still wants you to do the puzzle over.

I noticed one thing about TR-U: the saved game feature is messed up.

Sure it has checkpoints but still.

If I was to fire up the XBOX 360 right now and click on RESUME game at the default start screen, instead of taking me to the end of this level which is my saved game, 2 identical files in 2 slots, it will take me to Thailand.

Thailand was a long long time ago - it shouldn't come up when you RESUME game especially when the checkpoint has ding many many times since Thailand.