Problems selecting first gear.

[Storkfoot]

I have done three rallies on this Sx150 so far this year. I have been having very annoying issues with selecting first gear. I have deliberately done some miles in the hope that there would be some witness marks on some part of the engine to give me an idea as to where the issue lies.

If I am stationery at a set of lights, say, I have to rock the scooter back or forward to get it to engage first gear.

viewtopic.php?f=19&t=11852&start=80

I now have the engine out of the frame and can see that the gear shim has been taking a battering from the gear selector when I have been trying to engage first gear.

From memory, the shim clearance was about 0.20mm.

It is hard to see from these pictures but the gearbox stack does sit almost 0.1mm above the Layshaft.

My question at this point relates to the position of the gear selector when in first gear. The selector sits above the Layshaft. Is this normal?

[Knowledge]

My question at this point relates to the position of the gear selector when in first gear. The selector sits above the Layshaft. Is this normal?

HiPaul,

Sadly I can’t view the images on this device, but I am struggling to interpret the final sentence above. Are you talking about the wishbone when you say “selector”?

[Storkfoot]

Selector, sliding dog, cruciform for those Vespa inclined

Not the wishbone

[Cgt75b]

Is everything in good condition on top of the casing?

This can be an issue sometimes selecting first gear

Just a thought

Good luck in resolving the problem.

[Storkfoot]

Is everything in good condition on top of the casing?

This can be an issue sometimes selecting first gear

Just a thought

Good luck in resolving the problem.

Once I have started the engine, I don’t get that horrendous clicking as if the kickstart plunger is catching first gear. There is, however, a light grinding noise which clears once the clutch is pulled in. There is no contact between the clutch top plate and the kickstart shaft.

Sticky’s refers to some rear hub bearings causing issues with gearbox shimming. I can’t recall what make of rear hub bearing it is but it isn’t an original Innocenti. It appears flush in the casing and no leak of oil. The battered gearbox shim is, I think, about 2.05 so it isn’t abnormally large, or small. I am going to change the rear hub bearing to a new Scootopia one I have though.

Thanks for the reply I shall have another look at the kickstart mechanism in the chain case.

[hullygully]

looks like your 1st gear is almost flush with the layshaft? but should be slightly above
have you also checked the inside diameter of the shim to see if its smaller than normal?
also check the layshaft length against another where the gears sit

[Storkfoot]

Thanks for the reply.

In answer to your points, the internal diameter of the shim was 33.2mm. A sample of my others seems to show that they range between 32.9 and 33.4.

I now have 4 Layshafts. A - this is what has been fitted most recently, B - the invoice says this is a Casa Lambretta. It is not stamped Casa and I suspect that it is exactly the same as A which was an MEC/EUR Italian. C - this is one of the newish AF ones. I had this fitted originally. I took it out after discovering that I had an incorrect first gear fitted (now resolved). The case hardening around second gear has come off. D - is a battered old Innocenti one that I just keep to compare to.

You can hopefully see from the handwritten chart that the measurements of A to C are pretty similar. D, the original Innocenti, is the most noticeably different.

If I put the stack of gears (Innocenti GP125/200 gearbox with a replacement Indian GP200 first gear which is the same teeth and diameter as the Italian one) on all 4 gearboxes. In each case the gears stand proud of the Layshaft as they should. It is noticeable that the biggest gap between the gears and Layshaft, about 0.4mm, is with the original Innocenti Layshaft.

Going back to my query, the photo above with the steel rule shows what I am querying. When the gear selector is in the first gear position it stands proud of the Layshaft by about 0.5mm. Is this correct?

As I have had instances in the past were the ball bearings have been too big to pass through the Layshaft, I also measured the diameter of the channel which they sit in. All the aftermarket ones, A-C, are narrower than the original.

[Storkfoot]

On the issue of the light grinding noise I have had since the engine was built, I may have found what it is.

You can see a noticeable witness mark on the brass clutch thimble. It has been spinning against the top of the clutch when the clutch is not depressed. I think this is because the shiny stainless spring on the clutch lever is poorly formed causing the clutch thimble to jam open in the casing. I have bent the spring in a vice in an attempt to make it activate cleanly and return to its original position when the clutch is not depressed.





Time will tell.

[hullygully]

hi bud, it shouldn't spin cos it should be captivated on the operating finger

[hullygully]

as the selector is protruding past the layshaft, is it also protruding past the first gear making the shim rub against the endplate?

[Storkfoot]

hi bud, it shouldn't spin cos it should be captivated on the operating finger

[Storkfoot]

as the selector is protruding past the layshaft, is it also protruding past the first gear making the shim rub against the endplate?

Yes, I am pretty certain that has been happening which is why the shim is a right mess.

I have replaced the rear hub bearing albeit the dimensions of the new one are the same as the previous one. I am also changing all the gear selection mechanism and trying to find an Italian first gear ( I have one somewhere) in case the Indian first gear is the problem.

[Storkfoot]

This attempt is the same Layshaft (A), a new FA Italia gear selector and an Italian GP200 first gear.

The gear stack clears the Layshaft by 0.08mm. I think that’s probably okay. The selector, when in first gear, stands proud of the first gear by 0.04mm. That sticks out less than before and, provided it shims up okay to something nearer 0.30 than 0.07mm, it may be okay.

Thoughts anyone?

[hullygully]

[Storkfoot]

I have just dropped off the gear selector at a local engineers. I have asked them to grind 0.08mm off the gear selector. That way, the selector should not protrude above first gear when I engage first gear.

I’ll let you know whether the gearbox shims up okay and whether I can engage first gear easily.

[Storkfoot]

Update:

This was the gear selector when I picked it up, having had .08mm ground off. As you can see, this hasn’t touched all the prongs.



I put it all back together. It appeared to shim up fine with a 2.00mm shim but I still have the same issue. It remains difficult to engage first, is a bit clunky between second and first and there remains a bit of a grinding noise. On the plus side, it is a bit better than it was so I believe I am on the right track.

It needs to come apart again so I can have another go. This time, I am going to take the gearbox, Layshaft and gear selector in to the engineers to explain that 1. The gears need to stand proud of the Layshaft by 1.00mm; 2. More needs to come off the gear selector.

I am also awaiting delivery of an Italian Li125 second gear which is the same as the GP125/200 second gear. I suspect that the current second gear may be Indian.

[gaz_powell]

And we call thus fun.....

[Storkfoot]

And we call thus fun.....

Sourcing an original layshaft and gear selector is, perhaps, a more sensible approach. We’ll see.

[hullygully]

have you checked where the ballies run on the inside of the selector, not for grinding noise but for sticking? any worn or raised areas?

[Storkfoot]

have you checked where the ballies run on the inside of the selector, not for grinding noise but for sticking? any worn or raised areas?

Yes. The bearings run well in the channel. I replaced the spring and bearings the last time I had the Layshaft out, just in case.

The tone of the slight grinding noise has altered slightly which again makes me think I am on the right lines. But, if the channel is machined slightly out of position on the Layshaft, it may be difficult to fix. I am thinking that, if I have the Layshaft in my hand with the gear selector set to neutral then, if I spin first and second gear, they need to spin pretty freely of the gear selector prongs (dogs??).

I did try this and they did spin okay but perhaps they weren’t free enough.

As to any raised or worn areas, there is still, to my eye, too much wear around where second gear runs on the layshaft.