Opinions on this Layshaft please

[Storkfoot]

I am currently replacing gearboxes, endplates and probably now the rear hub bearing in an effort to find why I have (1) a grinding noise when going from first to second and (2) a rattle at idle that disappears when I pull the clutch in.

It’s a new build in that it was an empty casing to start with so, with that, goes the inherent difficulties to get stuff to match.

At this point, I am concerned about the bad witness marks on the Layshaft in line with second gear. The marks are noticeably worse on one side than the other. The edge catches on your fingernail. There are no noticeable witness marks on the inside of either second gear (AF Close ratio 4 speed and Italian GP200/125).

The engine was built before lockdown but I think the Layshaft was an Italian, MEC/EUR perhaps. Does it need replacing?

I know I need to get to the bottom of why this has happened

[hullygully]

have you measured the o/dia of the 2nd gear bud?

[dickie]

I'm digging around in my head to remember the issue I had with my 4 speed close ratio box. But either 2nd or 3rd gear was tight. I would definitely have been able to make it work, but if I had, it would have caused excessive radial force from the loose gear onto the layshaft; this in turn would have caused the lip that you mention. Also, it was not constant, it only occurred when a particular point on the loose gear coincided with another particular point on the cluster.

I can't be certain, particularly because I can't remember which gear was a problem, but if the same one, then I'd be confident that the gearbox had damaged the layshaft rather than the layshaft itself being an issue. Once there was a groove worn in, then the other problems, like a rattle, would be a result rather than the cause.

.......my pennerth worth.

[Storkfoot]

The GP200 gearbox that is in there now:

Outer diameter 2nd gear 109.9 (2nd gear cluster outer diameter 37.0) inner diameter 42.0.

The AF 4th gear cluster:

Outer 106.7 (cluster 41.9), inner 38.8.

The diameter of the Layshaft is 42.07.

I took the AF Close Ratio gearbox out as the gears really don’t mesh well with the cluster. I can’t verify whether the damage to the Layshaft happened when that gearbox was installed. It may be that it is happening now as the grinding noise is pretty bad now.

I found this thread. My Layshaft is AF, not Italian.

viewtopic.php?f=10&t=9049&hilit=+Layshaft&start=40

[Storkfoot]

I'm digging around in my head to remember the issue I had with my 4 speed close ratio box. But either 2nd or 3rd gear was tight. I would definitely have been able to make it work, but if I had, it would have caused excessive radial force from the loose gear onto the layshaft; this in turn would have caused the lip that you mention. Also, it was not constant, it only occurred when a particular point on the loose gear coincided with another particular point on the cluster.

I can't be certain, particularly because I can't remember which gear was a problem, but if the same one, then I'd be confident that the gearbox had damaged the layshaft rather than the layshaft itself being an issue. Once there was a groove worn in, then the other problems, like a rattle, would be a result rather than the cause.

.......my pennerth worth.

The biggest meshing issue on my AF was third gear not second, although that was far from great.

[dickie]

The biggest meshing issue on my AF was third gear not second, although that was far from great.

And thinking about it, that would cause damage right around the layshaft not just one side.

But looking at your layshaft, it must be caused by either excessive force being applied by loose second gear when you're in another gear (therefore it's rotating relative to the layshaft, OR a particularly soft layshaft. The second option seems less likely to me as I find it unlikely that it would be restricted to one gear only.

Which leaves the question about which gearbox was installed when it happened.

Obviously that's not an answer in itself but hope it helps clarify thoughts.

[Storkfoot]

The damage is right around the circumference but worse on one side.

I have looked at the gear selection whilst everything is apart. All looks fine. The sliding dog and pawls work well. I did fit a new MB gear swivel and selector rod when I built the engine. They appear to be the same dimensions as originals but I have put an old unworn rod back on, just in case.

A new MEC/EUR Layshaft is on order anyway as is a new rear hub bearing. The endplate fitted at present is a new Granturismo one. This replaced a SIL one which was difficult to shim. In the past, I have had non matching endplates that have been very tight on the gear cluster and/or the Layshaft. I do not believe that either of the endplates I have tried have been too tight.

Other things:

Clutch is a five plate built into an AF rear sprocket that is machined deeper. There is plenty of separation and, for this reason, I tried a 3mm top plate. That top plate caught on the kickstart shaft so I quickly took that back out and put the 2.5mm one back.

Kickstart lever is a Casa one. The splines aren’t a great alignment with the splines on the shaft but it doesn’t catch on first gear. I did think that, perhaps, first gear was rattling onto the kickstart pin teeth when the engine is idling (the annoying rattle that disappears when the clutch is pulled in). I haven’t entirely discounted this yet.

I could, of course, have two problematic gearboxes

[Storkfoot]

The biggest meshing issue on my AF was third gear not second, although that was far from great.

And thinking about it, that would cause damage right around the layshaft not just one side.

But looking at your layshaft, it must be caused by either excessive force being applied by loose second gear when you're in another gear (therefore it's rotating relative to the layshaft, OR a particularly soft layshaft. The second option seems less likely to me as I find it unlikely that it would be restricted to one gear only.

Which leaves the question about which gearbox was installed when it happened.

Obviously that's not an answer in itself but hope it helps clarify thoughts.

The horrible grinding noise when going from first to second. It also happens if you go the other way, from second to first at slow speed. Perhaps second gear is activated at the same time as first?? Just thinking out loud.

[Storkfoot]

have you measured the o/dia of the 2nd gear bud?

Thanks for this post. Second gear is the correct size but first gear isn’t, it’s 115mm and not 117.5 as it should be. Hopefully, replacing that with the correct one will remedy both the grinding between first and second gears and the rattle on idle.

If anyone has a 50 tooth first gear, 117.5mm diameter, they wish to sell please get in touch.

[hullygully]

have you measured the o/dia of the 2nd gear bud?

Thanks for this post. Second gear is the correct size but first gear isn’t, it’s 115mm and not 117.5 as it should be. Hopefully, replacing that with the correct one will remedy both the grinding between first and second gears and the rattle on idle.

If anyone has a 50 tooth first gear, 117.5mm diameter, they wish to sell please get in touch.

[roli150lam]

have you measured the o/dia of the 2nd gear bud?

Thanks for this post. Second gear is the correct size but first gear isn’t, it’s 115mm and not 117.5 as it should be. Hopefully, replacing that with the correct one will remedy both the grinding between first and second gears and the rattle on idle.

If anyone has a 50 tooth first gear, 117.5mm diameter, they wish to sell please get in touch.

i have one,it has several chipped starter teeth tho.
are you going to milnthorpe?i could bring it there with me.

[Storkfoot]

have you measured the o/dia of the 2nd gear bud?

Thanks for this post. Second gear is the correct size but first gear isn’t, it’s 115mm and not 117.5 as it should be. Hopefully, replacing that with the correct one will remedy both the grinding between first and second gears and the rattle on idle.

If anyone has a 50 tooth first gear, 117.5mm diameter, they wish to sell please get in touch.

i have one,it has several chipped starter teeth tho.
are you going to milnthorpe?i could bring it there with me.

Thanks, Roli. Yes, I am going. I think I may be sorted but I shall let you know beforehand. Thanks, mate.

[roli150lam]

ok .

[Leotech]

My mate had that gearbox in a fresh built motor and when it ran it made a knock knock knock noise, we took it apart and one of the gears you couldn't turn the gearbox by hand turning the clutch spider. It just went insanely tight.

We rang up to ask what to do, return it etc? and they said just grind a bit off where it was tight!


We took it out and put a SX200 box in and the close ratio thing was history.

[Storkfoot]

My mate had that gearbox in a fresh built motor and when it ran it made a knock knock knock noise, we took it apart and one of the gears you couldn't turn the gearbox by hand turning the clutch spider. It just went insanely tight.

We rang up to ask what to do, return it etc? and they said just grind a bit off where it was tight!


We took it out and put a SX200 box in and the close ratio thing was history.

Yep. When I ran the engine with the close ratio gearbox, it ran but was just noisy and a bit clunky. Turning the gearbox over by hand on the bench, you could see that the gears didn’t mesh well with the cluster, especially third gear. I could sense it would eventually end in tears somewhere along the line if I kept this gearbox in.

Therefore, I bought an Italian GP125/200 gearbox on eBay. I counted the teeth on the eBay advert and again when I got the gearbox. All good. However, I never thought to measure the outside diameter of the cogs even though I did see that there was no Innocenti stamp on the back of the first gear cog. On running this gearbox with a new endplate, it was even noisier with the rattle on idle. As I was “sure” I had a decent gearbox and an endplate that shimmed okay, I then started looking at other reasons such as the clutch. It was only when I saw the state of the Layshaft that I realised something was quite dramatically wrong.

If only I had measured the cog and identified it wasn’t right.

[Leotech]

I may have a 1st gear. I have a pile of one size. I've no SX200 / TV175 ones I looked for one other week for someone.

[Storkfoot]

I may have a 1st gear. I have a pile of one size. I've no SX200 / TV175 ones I looked for one other week for someone.

Thanks but I received one in the post this morning. It looks okay.

[Storkfoot]

I actually bought two new first gears, one Italian, one Indian. On the new MEC/EUR layshaft and with the Italian first gear, the stack of gears only protruded 0.4mm over the layshaft. The Indian first gear was 0.8mm proud of the layshaft. Sticky’s (page 81) says it should be at least 1.0mm.

I have been out for a few miles today but got preoccupied with sorting out the gear changing which was a but lumpy at first.

But, there is a very slight whirring noise that is noticeable at low speeds. I do have a new chain but it is not unduly under tension and it is not the kickstart engaging with the clutch. It is a much softer whirring, perhaps more like a soft grinding noise. I am thinking that it may be because of the lack of space between the layshaft and gears ( it’s shimmed with a 2.05mm shim and, from memory, about 0.2mm clearance). Does this sound plausible?

[Storkfoot]

I did a couple of hundred miles over the weekend. There is a little noise but you can’t hear it on the road. At some point, I am going to take the layshaft out again and get it fractionally machined to give a bit more clearance with the gear stack but, for now, I am just going to enjoy riding it.