Forum

[John R]

I am trying to replace some of the cogs in my 4 speed box. I have tried to remove one of them, small layshaft cog, without success. I have been using a suitable thee legged puller and have tried heating the gear, tapping with a hammer and using a long bar to turn the nut. No luck. Any ideas or anything I am missing?

[stinkwheel]

Is the shaft still in the gearbox?

It's been a while but don't remember anything in particular holding them on, should slide off. If it's still fitted in the bike along with the mainshaft, the cogs will still be engaged with the selector fork (which applying force to could bend).

By "nut" I presume you're referring to the nut on the puller? Because I don't remember there being a nut on the layshaft.

If it's the little 15t one on the primary drive end that's stuck and you have the layshaft out, I'd try sticking it in the oven then having another go with welding gloves on. Failing that, maybe try a hefty bit of steel tube acting as a slide hammer to drive it down off the layshaft (assuming the cog sticks out further than the dogs on the layshaft).

[PeteF]

That one can be a sod to move.
Are you doing a close ratio conversion?
Just warm it up some more is all I can suggest then get a wet cloth on the shaft to get the max possible temperature difference between the cog and the shaft.
If you have the shaft out of the box a local machine shop will press it off for you for beer money.
Where are you? Someone here might be able to help. I have a hydraulic puller which would probably do it.

[John R]

Hi Both, yes I'm doing the close ratio conversion- however, the one that is stuck is the one on the layshaft, which I am replacing because it is in poor condition. All the other cogs in the box are in good condition, and I have removed the relevant cogs for the close ratio conversion without too much struggle. Why should that one cog in the box be chipped and worn? Well perhaps a previous owner overhauled the box, renewed the cogs, but couldn't get the layshaft 15t off either and left it there!

I'm down in New Milton, Hampshire, not exactly a hub of engineering, though I have had some help from Sammy Miller's museum in the past.

[stinkwheel]

If it's going to cost more than £64 to get it off, that's what a new layshaft costs.

[vince]

Hi, is the box redditch or Chennai? as I have had to use a press to fit the latter. Also have you removed the splined bush from the shaft first? Vince

[John R]

Chennai box. I took it to a local mechanic, who remarked that the dogs on the shaft were pretty worn as well, so I'm contemplating replacing the shaft. It probably implies that I should replace the mainsheet components but i'm way over budget already.
The splined bush is easy to remove.