Hello,
I made a soldier for my game and i rigged him, I also have a seperate gun model for him and i want to combine the gun model with the soldier but when i press the combine button, my weightpaint tool stops working(It doesn’t show the colors anymore). Does anyone know how to combine these 2 meshes properly?
I don’t know if Maya can combine skin weighting along with the meshes (though there’s no reason it isn’t possible), but since you’re just combining with a simple prop that probably doesn’t have complex weighting, you can just re-bind the skin (Skin > Smooth Bind), then copy skin weights from the old character mesh to the new combined one (Skin > Copy Skin Weights). The prop will have bogus skin weights, but you can now re-paint them (which is probably trivial for a simple rigid prop).
(Personally I’d avoid combining a prop with a character, but I don’t know what you’re doing…)
since 2015 (one of the later SPs if I remember correctly) the polyUnite command has got a new version.
polyUniteSkinned
In the Mesh>Combine menu you can access that by ticking on the Combine Skinning checkbox.
That will combine all selected objects preserving their skinCluster info.
Thanks for the reply’s. ticking the combine skin option worked. i did this before but it didn’t work then. after restarting maya it worked 
cheers,
Jelle Booij
Thank you for that tip in the combine options!
Another question: Now the transforms of my Character are left and they’re not non-deformer history.
I bought a character witch was rigged and separated. Very odd. My job is to combine all the pieces into one mesh and merge, without losing the skin weights paint. ^^ Do you have and idea how to do that?