This may have been discussed before but I can't find a thread on it. The gearbox on my M20 leaks oil from around both the gearchange shaft and kick start shaft where they pass through the gearbox end cover, I guess this should not be a surprise as they are plain metal shafts running through plain metal bushes with, so far as I can see, no form of any seal to keep the oil in. Both the bushes are new and although the shafts are original there is negligible play in them. The oil is just part way up the gearbox filler neck at the moment but continues to leak out. Has anyone any suggestions as to how I can keep the oil in or should I just let the oil run out till it stops and leave it at that level?
The bike is still not quite finished yet so all these observations have been made while on the rear stand. The oil level is now 5/8" below the top of the filler neck (the filler neck extension on the gearbox casting is about 1 1/4" tall so about half way down) and has stopped running from the gearchange shaft as that is now about level with the oil. It is still leaking from the kick start shaft which is lower. Once I get the bike running and off the rear stand this will lower the back of the gearbox which is only going to make it worse? I solved this problem on my G3L by stripping the gearbox and packing it with liquid grease which it has been quite happy with these past 20 years but I was hoping not to have to do that with the M20 as the gearbox otherwise seems to work fine having checked its operation using the guidance in the technical section.
I think you might have overfilled it Mike.
I have produced some notes offering corrections to those in the technical section.
Though they are generally correct in theory.
I think there issues with the size of the paws, but I want to address that with mine before I commit to paper.
Although the idea was to keep dirt out, this may slow down your weeping.
Mike, unlike the Burman and Albion boxes, the M20 box should NOT be run with grease. There are small drillings and oilway in an M20 box that require lubrication with engine oil only. Regards Ron
Thanks for the update Ron, I had it in the back of my mind that I couldn't use liquid grease in the M20 box but couldn't recall why! Mark, it may be that I have a little too much oil in the box though in the thread 'Gearbox oil overserviced' Ians advice is to fill part way up the filler neck, half is I suppose part way but far from the 'Keep full' as written on the filler plug. Your adapted bush may well do the job. I'll have to take the end cover off and measure it .
Many thanks
