I presume this is an 8 cell pack.

I am new with the electrajet.

I would guess that this might be getting a bit heavy for the stock motor. Or, perhaps your CG is too far forward. Have you balanced it? Where do you have the CG set?

I am flying mine on 7 cell 2/3A 900 MAH nimh pack from my Aerobird. It is not a hot performer with 7 cells, but it flies fine. the batteries are about 2/3 of the way forward in the equipment bay.

I also have an 8 cell KAN 1050 mAH nimh flat pack. Haven't tried it yet, but to get the plane to balance I had to move it so that it sat about centered in the equipment bay, a little closer to the back of the plane.

Make sure you are checking the CG. Mine is set about 3/8" forward of the molded CG marks, or about 8 1/2 inch from the point where the wing front meets the fuse.

Hope this helps.