Author Topic: 2 3/4 hp 1920 3 speed gearbox stiff change  (Read 4749 times)

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Offline dodursley

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2 3/4 hp 1920 3 speed gearbox stiff change
« on: 10 Nov 2007 at 15:31 »
I have recently purchased a 1920 2 3/4 hp with 3 speed box and gearbox mounted clutch. I am finding it very difficult to change gear, very stiff and will not keep the gearchange settings at the quadrant. Seems to be little movement of the selector at the gearbox for each gear position.
All worked when I took the springs out of the selector tube, but I assume it needs some spring to re centre the selector fork after changing to another gear. All the gears/shafts/bearings looked good, when n years of baked oil/grease were cleaned off.
Can the spring pressure be reduced to lighten the gearchange or would this lead to multiple gear selection?
Could do this by making a longer bolt &/or making a set of lighter springs.
Comments and suggestions please

Offline Alan Cun

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #1 on: 11 Nov 2007 at 08:12 »
please refer to accompaning post brought forward originating from Cardan.  Al

https://www.douglasmotorcycles.net/index.php/topic,2299.msg8324.html#msg8324



[link added. 11nov07 -Doug]
« Last Edit: 11 Nov 2007 at 15:58 by Doug »

Offline dodursley

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #2 on: 21 Nov 2007 at 19:26 »
please refer to accompaning post brought forward originating from Cardan.  Al

Reassembled box after cleaning, did not screw nut holding springs and forks  down as tight, reducing pressure a bit. Also put thin gasket on gearbox joint as the cleaned box locked up when bolted up! Now spins freely and the gears select OK when running on the stand, which is better than before. Have not road tested yet but appears promising.

Edit: Quoted text separated from reply. A.
« Last Edit: 21 Nov 2007 at 19:42 by alwyn »

Offline Domas

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #3 on: 05 Aug 2022 at 10:59 »
Which oil do you put in?

Offline cardan

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #4 on: 06 Aug 2022 at 03:57 »
Hi Domas,

There's only some bearings and gears in there, so any heavy weight gear oil should be OK. Some use semi-fluid grease which would also be OK, however real grease will cavitate and leave things unlubricated. I have a little Belgian FN - they lubricate their gearbox with engine oil via a two-way tap. I recall Sunbeam did the same on some of their early machines. So anything oily will be OK - just top it up after it has dripped onto the garage floor!

Leon

Offline graeme

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #5 on: 07 Aug 2022 at 04:05 »
Semi fluid grease is definitely the go - it doesn't leak out like other oils do! When putting it into the gearbox it is advisable to warm the fluid up, it is very thick indeed and takes forever to flow otherwise

Cheers, Graeme

Offline cardan

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Re: 2 3/4 hp 1920 3 speed gearbox stiff change
« Reply #6 on: 07 Aug 2022 at 08:47 »
Lately I use Penrite Transoil 250, which is a super-thick and additive-free, but at least it pours. I reckon anything wet and oil is probably ok in a vintage gearbox - it's the dry gears that are stuffed!

Leon

 

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