Has anyone made one or know of any tutorials?
I really need to know how to build the base, I can't seem to wrap my mind around this one.

Could it be something like this?
It is not a big cake - something like a big loaf pan - and all the modeling was made from a tall rectangular cake.
Here is a second view.

Majka

P.S. Your cupcake cake is wonderful, even when not exactly as planned. Sorry you had so much trouble.

Great cake, I'm gonna save that pic.
Turns out I don't need to make the motorcycle cake but just the cake topper. So whew thats a relief.
Thank you, I'm glad it's over and it turned out pretty cute. You live and learn I guess.

Hi Majka_ze ,

Your bike cake looks really nice. I need help I want to do a cake similar to yours. My son's 21st birthday is less than 2 weeks away and I really want to do him a nice 3D motorocycle cake. Can you supply me with detailed instructions?

Thanks for your help.

It is not mine cake but comes with instructions - bake 2 cakes in loaf pans. Torte each cake twice, getting 3 layers. Make a 4 layer cake, at one end make it longer - cut one of the two remaining layers in half, make a 2 layer cake and glue it with buttercream at one end. The last layer is needed for the details - glue it where needed - front hood, tank, seat. Put it in the freezer. Cut out the details - tank and wheels.
Crumbcoat and fondant.

I would probably use a 16" x 12" pan I already own. Bake the cake (not full high, one layer). On the longer side measure 10" , mark. Cut. Now you have one cake 10" x 12" and one 6" x 12". Cut the bigger cake in thirds - getting three cakes 10" x 4". Use one of them as template, cut from the rest one layer more. Fill the cake, getting one relatively high 10" x 4" cake. Freeze it for easier carving. Use the rest for cake spackle - you can build up where needed.

Print out a side view and top view of the motorcycle you want to make. Using the side view as template, mark the wheels and the tank. Carve the form. You want to get the rough form, it isn't necessary to get all the details. You can always build up the cake with cake spackle (under the fondant) or with fondant (under or on top of the fondant).

If you need the cake bigger, you can either use the motorcycle as top tier over rectangular / round / oval cake, depending on what looks best for you, or make it bigger. In this case, over certain height you would need to handle it as 2tiered cake with the same dimensions - meaning supports etc.

Good luck to you!