few months ago while contructing trumpheter BMP-2,I notice the rubber track is little short! fortunately the gap was hide behind the side skirt.
or do anyone encounter similiar problem?

Can not make any comment on the length of original rubber bands, unfortunately. But I am sure that's a major (not the only) drawback of the kit.
I didn't hesitate and ordered metal tracks made by MasterClub and can swear, that was bloody good decision. The quality is amazing, resin pins work well and they fit together without any special cleanup, no glueing... Have the same experience with BMP-1 and BMD tracks, so I can recommend. A bit pricey, but there are more pros than cons.

unfortunately that's right, I had the same problem with this kit.

I dont have the kit in front of me, waiting for the price to fall, or to build all these old DL kits, or...

Is there any wiggle room in either the idler or sprocket placement?
I do know that the T64 kits with the link to link track were a half link too short unless you shaved off the mounting points for the front-mounted idler and slid it back as far as the cutout in the side armor would allow. Then perfect fit.

Is the idler mount a simple round peg or does it have a squared off portion at the bottom?
For other kits with track fit issues, I have rounded off the hull side of that placement, allowing a small amount of rotation in the idler mounting arm, which lets you get the track tension (tighter or looser) you want.

All that said, I do think that having rubber band tracks in a kit at this price point is a bit of a raw deal. Especially tracks that look this poor AND dont fit ootb.

Mike
My US$0.02, your mileage may vary.

Thats strange, I used the Trumpeter AM LTL track set and had no issues what so ever with my two T-64BV builds.

Steve Z built one OOB for a book project and I asked him if he had issues with the track and no problems reported.