The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Gearbox, Clutch, Primary => Topic started by: Superflash on 20.03. 2021 22:39

Title: Gearbox plunger
Post by: Superflash on 20.03. 2021 22:39

So mucking about with the gear box due to it jamming up. First drama sorted when I discovered that I was missing 2 washers. 1 behind the 1st gear pinion and the other behind the kick start spring. One thing I noticed was that the plunger has what I'd describe as a bullet tip. Looking at the parts drawing it looks more like a blade tip. To me the bladed one would give a more positive engagement with the cam plate. So.... leave well enough alone or change it for one of the bladed one? Cheers

Title: Re: Gearbox plunger
Post by: Greybeard on 20.03. 2021 22:54

My 1955 sprung frame bike's gearbox has a bullet shaped detent plunger, (I don't know if that snippet of information helps)  *smile*

Title: Re: Gearbox plunger
Post by: Superflash on 21.03. 2021 00:07

Cheers GB. I guess if it works then that's fine.  I just wondered if the bladed one was a design mod that worked a bit better than the bullet type.  Cheers Tony

Title: Re: Gearbox plunger
Post by: trevinoz on 21.03. 2021 21:00

I think that the blade type plunger was in the early boxes. I have one here in pieces.

Title: Re: Gearbox plunger
Post by: Minto on 21.03. 2021 21:43

Sorry to butt in but, what does this plunger actually do? I know that's a novice, schoolboy question, but that's what I am.

Title: Re: Gearbox plunger
Post by: berger on 21.03. 2021 22:29

minto it is spring loaded and provides pressure into the cam plate valleys at each gear change to hold the selector forks in position, if the pressure wasn't there you have a very good chance it will jump out of gear

Title: Re: Gearbox plunger
Post by: Greybeard on 21.03. 2021 22:43

Detent plunger:
https://en.m.wikipedia.org/wiki/Detent

Title: Re: Gearbox plunger
Post by: Minto on 22.03. 2021 00:56

Cheers for that, every day's a school day.