Hi Longton
You probably have the "old" set of parts between the output bearing and big circlip. As far as I can remember these comprised, firstly the bearing which should have been press fitted at 150/200 DegC into the casing - in as far as the aluminium flange. Then there was an oil-seal, then a spacer which looked like a piston ring, then some thin slightly "crinkley" spacers/washers and finally the big circlip. Between the output gear and the chain sprocket is a spacer which acts as the inner for the oil seal.
There is now a much better arrangement which can be bought from Draganfly - at 01986 894798.
This comprises basically a new spacer with oilseal which fits between the bearing and the big circlip - with maybe the crinkley shims/spacers to take up any slack. This provides the correct spacing from bearing outer to the big circlip and should take up the 3.6mm slack.
I think the parts are 3112-96 and 3635-96 from Draganfly and cost about £16.
The oil-seal inner still runs on the spacer between the output gear and drive chain sprocket. A new one can also be obtained from Draganfly if your old one has a groove worn into it by the oil-seal, - though sometimes a good bit can be found by putting the spacer on the other way round !!.
The output bearing is a very unusual size by the way - 72mm outside, 1.5 inches inside and 17mm wide, and a sealed one (I left the seals in on mine) can be obtained at a reasonable cost from:-
Peter Barker -
barkers@engrs.wanadoo.co.uk 01454 228066
If you look back to page 5, 20th December, (if I've got the page right) you will see that my old box, unknown to me, had been modified with a sleeve to take a standard sized bearing. This had worked for many years but eventually all worked loose and in the end I was lucky enough to find another gearbox casing and shrink in a new "special" but standard Burman sized bearing.
Hope this is of some help.
Matty