Author Topic: Gear box adjustments  (Read 2810 times)

Offline LJ.

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Gear box adjustments
« on: 21.12. 2007 09:32 »

Well, I can now say that I have got my six spring clutch adjusted correctly and all is working well with that. But! I am getting nasty gear changes, sometimes when neutral is selected there is a grinding of cogs until I lift lever to get neutral properly. It's funny that I never had this problem before I restored the clutch. *conf*

I read somewhere, and I cannot for the life of me remember where this was... Something about adjusting the nut under the gearbox. (1961 swingarm A10) What exactly does this nut do? It is really a bolt with a lock nut on it. I'm told that you must not touch this as its factory set, but it's highly likely in the last fifty years that it has been messed around with. I have not been out to look at the manuals yet, but I gather that it may be something to do with the cam plate adjustment. How much should I turn this bolt? half/full turn?? clockwise or anti?
Ride Safely Lads! LJ.
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
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Online BSA500

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Re: Gear box adjustments
« Reply #1 on: 21.12. 2007 10:35 »
That would be the gearbox indent plunger?.I have read that it should be set with 2/3 threads showing.Well I did that once and found I could not even change gear it was so stiff!!!,Now I just do it by feel just wind it out half a turn each time until it gives a smooth and light action.If you didn't know it pushes a plunger into the gearchange camplate to prevent it skipping gears on changing,so too tight and the change is stiff and too slack and there is no positive clicks and the danger of missing gears.Does that make sense the way I have written it.

Online groily

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Re: Gear box adjustments
« Reply #2 on: 21.12. 2007 18:28 »
Makes perfect sense - and I agree there's no need to get hung up about 'factory settings' . . . the spring-loaded plunger needs to be  screwed in far enough to give positive changes - and not so far that the cam plate can barely rotate from one indent to the next and everything from the gearchange lever inwards gets stressed. No harm can be done by playing with the screw and locknut - but if you take it right out the oil will come too. (Good chance to check the state of the spring etc if you do take it out though). Strongly recommend having a look at a diagram of the camplate, plunger and selector rods/forks arrangement to see exactly how it all works - tho don't have one to offer I'm afraid. I discovered all these things the hard way a few weeks ago, so it's all very fresh!
However, if the gear-change characteristics have changed for the worse simply as a result of a clutch job, I'd suspect the fine adjustment of the clutch too, I have to say . . . maybe a bit of drag there? Springs a tad too tightened up, push rod not lifting the pressure plate quite far enough, etc? I'd certainly play with those aspects before attacking the plunger, but the good news is it can't be anything too serious. Groily