Forum

[Himself]

Thanks Adam. There's no interference between gear lever and footrest. The end of the détente plunger is rounded and I wonder how sharp the wedge ends on a new détente. The inner ratchet on the foot-change mech seems a bit worn and I was thinking of replacing these to see if this would do the trick; the cost wouldn't be great if these don't work. I'm expecting to have to strip the gearbox. Will keep you posted. Actually, mention of adjusting the primary chain makes me wonder how sensitive the gearbox is to maladjusted chains. When reading the 4 parts of the Technical Notes documents I noted the author almost implies slack chains could affect the operation of the gearbox. At some stage the gearbox sprocket has been changed to a 17 tooth one so it's possible the gearbox was dismantled previously. I'm not sure if there's grease inside the gearbox or only oil. I should have changed the lubricant by now but was waiting until everything is working before doing so.

[PeteF]

Slack chains, primary and final drive can definitely effect gear change but shouldn't cause you problem of slipping out of gear.

[Himself]

I fitted a new detent plunger and an inner ratchet mech to the footchange but still slipping out of 1st gear. Decided to dismantle gearbox while still in frame to find the clutch centre retaining nut was very loose and I didn't need a clutch extractor to remove clutch centre from mainshaft; it came away by hand. I'm hoping this is the cause of the problem and that when I tighten the clutch centre onto the mainshaft properly the slipping disappears. There doesn't seem to be very much wear on the dogs of the gearbox pinions to my uninitiated eye.

I noticed that the gearbox mainshaft has a woodruff key fitting machined into it at the gear-change end as opposed to the clutch end. Its only purpose seems to be to engage with the thrower washer. How important is this as my gearbox doesn't have a woodruff key fitted.

[Mark M]

What looks like a Woodruff key slot is actually a slot for a tab washer that should go behind the mainshaft nut on the footchange end. At least, that's the case on the Redditch Albion gearboxes, not sure about the Indian ones. I'd look on the parts list but I'd lose this reply!

REgards, Mark

[JTL]

What kind of part is the detent plunger? I'm experiencing gearchange problems too, and when reading old posts about the subject the detent plunger keeps coming up. As Himself has found out nothing is shown or listed in the online parts book. When searching on the part here at Mr H's site only old posts are referred to; no parts in the online parts book. What part # has it? Himself, may you as a newly enlighted can explain to me what this small magic gearbox part is doing? Thanks and sorry for hijacking your thread... Jacob

[Steve T]

Jtl this is the indent on my 2002 4 speed right change maybe yours is the same

[Steve T]

Sorry that meant to read detent plunger number 25

[JTL]

Hi Steve...Thank you. My gearbox is the same, but I've been looking in the wrong direction. Also been confused about the different names for the part. In this forum it is called "detent plunger" and in the parts book it's called "gear operator selector assembly". I guess the assembly part of the name refer to the spring mentioned in this thread (?). But what does it do; what part of the gear changing operation does it controle, since it plays such a vital role in changing the gears?

[Mark M]

The "detent plunger" is a positive stop mechanism. It was the great innovation of gearboxes in the 1930s. Before it's invention the lever that moved the gears simply pushed the gears along the shafts until you the rider, decided by skill and experience that they were in the right spot to supply the gear ratio you wanted. You then let out the clutch and if you were lucky or practiced, you had a gear. If you were neither you got a grinding noise or no forward motion or even both. The problem for designers was to create a device that would allow exactly the right amount of movement to get to the next gear (and no more than necessary!) without preventing you moving easily to the next gear up or down when you next needed to change gear again. And also ensure that the lever did not drift out of position once in a gear. Early gear change levers often had slots cut into the support bracket (usually mounted on the tank) to approximately co-incide with the correct location of gears. However, adjustment was needed regularly and could alter on a long ride as the box warmed up. I rode a 1924 Brough Superior recently with a 3 speed hand change with no positive location and it was hard to find the gears at all at first! Later devices (patented by Velocette,) were located on the outside of the gearbox and had a lot fewer lever joints (and so less "slop" in the mechanism) and were soon accurate enough to allow the rider's foot to do the work instead of relying on the ability to "feel" the gears by hand. The spring loaded plunger and it's reference arc (the swinging fork) located inside the box were the next step and improved the reliability of the box greatly. However, the purpose of the plunger itself is still to locate the ideal position for each gear once it has been correctly adjusted, which is what the inner case mechanism does. All of which means, adjust gear selection in the outer case and set amount of lever pressure on the plunger according to personal taste. Apologies if I've missed/mistaken anything!

REgards, Mark

[Himself]

Thanks Mark for explaining about what I thought was a Woodruff key slot on mainshaft. I was wrong about the detent not being present in the gearbox drawings; JTL points out correctly it's named gearbox operator selector. I got confused because my workshop manual fails to mention the purpose of the detent/selector and that it can be adjusted. I suggest to JTL that he reads the Technical Notes documents on the Albion gearbox