optima gearbox

[flintstone]

Hi. can anyone please help me? I'm rebuilding my koysho optima and within 10 minutes have ran into difficulties. when I have assembled the gearbox the shaft for the final pinion seams too long and is pushing the outer gear so far out that the outer gear cover will not fit over the gear.

If I slide the final pinion further down the shaft, the outer gear is in the correct position but shaft is so tight against the casing it stops everything rotating.

I know the problem is my incompetence and not the the parts because there are no new bits.

what am i doing wrong.?Please help....