I am busy attempting to assemble Technic 8071, and have encountered a problem.

On page 83 of the first manual, a yellow gear (4203493) together with a grey splined rod (4211815) is added to the sub-assembly in diagram 13.

A little later, in book 2 page 4, diagram 14, two sub-assemblies are being joined, but the yellow gear is in the way. If you remove the yellow gear, everything goes together just fine.

I have backtracked through the instructions and re-assembled everything carefully, but there remains the possibility that I have made a mistake. Right now, it looks to me as though the documentation is incorrect. Can anyone confirm either that they have encountered the same problem, or that on the contrary, they have assembled the kit successfully? Is it just that I'm looking the wrong way at the diagram?

Edit: Added a couple of pictures

With yellow gear in placeWith yellow gear removed and other sub-assembly in place

  • 1
    I have now realised my error. the smaller sub-assembly was incorrectly put together. The manual is correct. Thanks to all for your help. May 21, 2013 at 18:25
  • Well that's actually a nice concept for a contest (I mean, we're all tired from build-in-the-bag, right?): mirror building!
    – Joubarc
    May 22, 2013 at 4:26

2 Answers 2


Seeing the manuals, I'm fairly confident the instructions are correct.

The 11L beam from the second part (introduced in book 2, p 2, #1) looks like it should slide right next to the yellow gear (thus, not right on top of the right 7L beam (introduced in book 1, p 79, # 4) but one stud to the right, which shouldn't be a problem). To clarify, the 11L beam should be exactly in the middle, at equal distance of both yellow gears, right on top of the part with three holes protruding from the turntable on the right.

I'l admit I didn't build it myself yet though, so maybe I overlooked something.

Moreover, I don't really see what could go wrong, especially in book 2. Even in book 1 I can only imagine swapping the right 7L beam with the other part in #3 of page 79, thus having the two 7L beams next one to another, but that kind of mistake should be easier to spot than to make. Could you perhaps post pictures of the two parts as they are before you attempt to assemble them together?

  • I've added pictures. I hope this makes my problem clearer. May 21, 2013 at 18:20
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    Indeed it does. Your small part (the one with the white beam) looks like it's mirrored from what it should be. The 11L beam should be on the right side, not the left one.
    – Joubarc
    May 22, 2013 at 4:25

enter image description here

This is the image from the Book 2, Section 14, Page 4 on the instructions from the Lego Website - source. Does yours look like this?

To me it does look like it's not quite right - if you lift the yellow gear out, move the second part into position and then put the gear back it in it looks like it might fit, although the yellow gear wouldn't turn.

I'd advise contacting Lego support, or see if you can pick out the way the person put it together in this YouTube timelapse video.

  • The timelapse is interesting but goes way too fast... However, considering no-one posted a comment about a mistake, I find it hard to believe there is one.
    – Joubarc
    May 20, 2013 at 20:22
  • I have this set and didn't encounter any problems. Not at this step, not at any other. (Unlike with easily a dozen other sets, where the instructions were wrong, in point of fact, in all kinds of ways and for all kinds of reasons, so I know LEGO aren't impeccable.) And everything was functioning properly when it was assembled. Sadly I've long disassembled it, so I don't even know what all these gears did anymore. And of course I don't remember by heart if my instructions actually looked the same as in the image above, so I guess I will have to check that to be completely sure.
    – RegDwight
    May 21, 2013 at 10:12
  • Yes - that's pretty much the same image. Lifting the gear out doesn't help. It's really in the way! :-) May 21, 2013 at 18:18

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