Originally Posted by Dmitri Tech

I am on gold coast australia and plan to run at a indoor clay track where people of reported in this thread problems of stripped idle gears.

I am in process of switching to mid motor and would like to use your experience to help prevent myself and other people from having this problem.

I did a quick pic with mobile phone and messy text to try to show a picture of what i am seeing as the issue.

I am working with what i have
Page 23 of the manual states to use 2 x 0.5 shim/spacer (i didnt have them as i purchased 2nd hand roller with new mid motor kit-unused)

I did have
1 x UM726 that has a 1mm shim + 0.5mm shim

With 0.5 shim there was a gap on top screws mounting into Red Exotek rear block.
With 1mm shim it seems perfect, to show i can slide a very slim bit of paper under rear of gear box (less than 0.5mm)

Thoughts?

Edit uploaded better quality pic no gearbox