Gearbox problems

[G.I]

I've rebuilt a 150 special engine but can't set up the gears.

New bits include...

Bearings/seals
Sliding Dog
Selector pins, balls and spring

Old original bits include

Gear cogs and cluster
Selector wishbone
Layshaft
End plate

It all fits together well and shims up nicely.
The 2 piece selector shaft is aligned correctly in 2nd and 4th according to the good book.

Will move through all gears freely either using the handlebar selector or just the selector shaft with the rest of the linkage disconnected.

But there's a neutral between 2nd/3rd and 3rd/4th.
It doesn't take much to knock it out of the neutral and into gear but it's obviously not right.

I've tried another gearbox and it's still showing the same problem.

Can someone please take a guess at what I've done wrong so that I can get some sleep tonight.

Cheers.

[Captain Pugwash]

There is a neutral between second and third, and third and fourth or you wouldn't be able to change gear from one to the next.

What's probably happening is the selector is most likely dry and the ball bearings are dragging over the raised sections as you slide the gear arm to select gears.

Once the gearbox is Filled with oil and the cables are connected with the engine running you will likely find its working as it should.

Unless you've done somthing I'm missing.

Mark.

[G.I]

I had it filled with oil, cabled up and running. It sounded fine with no noise from the gearbox.
It was only when I tried shifting gears the problem became apparent.

Now it's stripped down to the end plate and clutch spider but still not working.

[Captain Pugwash]

I had it filled with oil, cabled up and running. It sounded fine with no noise from the gearbox.
It was only when I tried shifting gears the problem became apparent.

Now it's stripped down to the end plate and clutch spider but still not working.

Maybe there's someone local to you that's on this forum that could offer some help, as I think it needs a good coat of looking at.

Sorry im not much help, I hope you sort it.

Mark.

[G.I]

Thanks for trying.

It'll end up being something stupid I've done but it's driving me mad at the moment.

[hullygully]

before you stripped it, could you sellect the gears ok then?
have you placed the gears back in the correct way round?

[G.I]

It's an engine case and gearbox that I haven't used before.
Apparently it was running but who knows?

The gears are in the correct way, no chatter with the engine running in neutral or in any gear.

I'm completely out of ideas now and starting to think the Captain was right and the balls are dragging on the high spots of the sliding dog.
I'm just reluctant to build it all up again only to find the problem is still there.

[Wack]

There's some dodgy selectors about, they look 100% machined and shiny compared to a SIL one. Best bet is endplate off, hub on, slide into 4th and fit gear noting the selector dogs line up perfectly with the 4th gears internal dogs. Then knock into 3rd and fit 3rd gear and check again, until all gears are fitted. If it is a dodgy selector you will notice that when in neutral the dogs sit on top of 2nd gear instead of having a slight gap and the selector dogs don't match the gear dogs. Here's the dodgy one with pics showing how it doesn't line up correctly compared to the SIL one in the last pics

[G.I]

Cheers Wack,

The selector is an SIL item from SR.
it's nowhere near machined and shiny - took quarter of an hour with a file to knock the burrs off!

I did as you suggested and everything lines up as it should.

I finally changed the balls and spring back to the old lot and it appears to have reduced the problem quite a bit.
Perhaps I just have to ride it and knock the newness out of it?

I'll let you lnow.

[soullad]

Also some combinations of gear selector rods and pawls do not work. I've ended up changing gear selector rods and this cured my gear selection woes. Really frustrating mind.

[hullygully]

check also that the 2nd & 3rd gears are actual 2nd & 3rd gears, as you have to check, as well as the no. off teeth per outside dia, the layout of the internal diameters selector points
what I'm trying to say is you could have 2 x 2nd gears

[Ken Tucky]

G.I,
Apart from all of the other very good, helpful advice.........you've already eliminated one variable by trying another gearbox, so good for you.
Your symptoms sound like your gear selector spring may not be strong enough?
Even if you have a new one it doesn't necessarily mean that its OK.
If you can't get hold of a stronger spring by buying one, you can fettle a kickstart plunger spring, if you've got one knocking about, but you may have to fettle it by shortening a little - i.e. so that the coil bound length more or less matches what you have already got otherwise the balls will not go in far enough to allow for the cursor to move.
Btw, I use Indian selectors in my sprinter, can't afford Italian ones as I wear them out fairly frequently and yes some of them are bit dog IMO.

Below is an earlier post, I put up some time ago, about gearbox woes if you're interested, another problem - it relates to the selector wishbone ...........

Hope you solve it.

Richard

Having been sprinting for many years and undertaking many/read - 'very many' gearbox strip downs you'd think that I'd have got the hang of it by now.
So if its of any help/consolation - about 4/5 years ago I was upgrading just about every moving part to do with gear selection in my sprinter, to remove any sloppiness.
I put a non innocenti gear selector - the part with the pawls on it, (not a selector cursor/sliding dog) in, brand new...................
I must have stripped the gearbox 20/25 times, I'm not exaggerating btw, because I either couldn't get fourth or couldn't get first and could not get the bell crank lever to sit in its rightful position in neutral.

I ended up putting my 'old', Innocenti selector arm' back in.

When I finally got around to checking this in another engine down at Chiselspeed's it was found to be impossible to build - it looks like the splines had been wrongly machined in the arm, so it was never going to build was it.

This may not be your problem - in your case it maybe that you've just got to move the arm on the splines to get it OK.

A bit extreme perhaps, but if its happened to me well ................it could happen to anyone.........