Xtr 970 cranks installation problem

Hi I just got some new XTR970 cranks off ebay and I am having trouble installing the left non-drive crank arm. If I put the left arm on anf tighten the alloy 8mm allen bolt the left arm only pulls on partially so that half of the splines are still visible even when the bolt seems pretty tight. (45-55Nm specified). The crank splines look fine and for the life of me I can't see any reason why the left arm won't just pull fully up the splines. i tried a rubber mallet to see if that would make the crank home fully seated but it didn't. The arm is still pretty easy to remove after tightening the bolt.

Do I just use a bigger tor

have you loosened the collar?

Premature posting there. I was going to say just tighten with more effort and risk stripping the bolt or is there anything I am missing? Even with the collar loose and removed from crank arm (thanks for the suggestion dirtyrider) and dust cover removed it is impossible to tighten with a normal size 8mm allen key. Maybe I'll just try again with an allen key mounted in a long wrench.

thats the thing i dont like about these cranks – you have to use a lot of **** force to install them and to remove them – there's a reason why xtr 2011 has gone back to using two allen keys

when i installed mine i went way past the recommended torque to get them on. Crap bit of design IMO

I agree with above – i rode around with some of the splines showing – it started to slip 😥

Got home, bigger allen key (wrench) and gave it some welly! Hasnt moved since, really crap design IMO why cant it be the same as XT!

Thanks guys. Ignoring the recommended torque setting and using a bigger wrench, the arm pulled up the splines O.K. Seems a bit of a faff compared to the XT cranks that I took off. ;o(

It's a s*** piece of design. Have you got the slim metal washer between the bolt and the inside of the crank arm? If you're not sure check ASAP!