Clacking sound in rear tranny/variator

Hi!

I finally got my 85 Vespa Si, and it got a clacking sound in the rear when accelerating under load (with my weight on it). It also struggles with getting going, like something is holding it back.

When it sits on the center stand with rear wheel in the air, it accelerates smooth and without noises.

It had this noise when I bought it aswell, but i figured it would dissapear after rebuilding the transmission with new bearings and stuff. It didn’t..

It is a variated SI, with stock variators front and rear. Clutch and all parts in driveline are stock.

Re: Clacking sound in rear tranny/variator

DrGeorgeTompson (Alan) /

Starter clutch?

Are your gears healthy looking?

Re: Clacking sound in rear tranny/variator

> DrGeorgeTompson (Alan) Wrote:

> -------------------------------------------------------

> Starter clutch?

>

> Are your gears healthy looking?

If they were bad, wouldn’t it be difficult to start? It starts super easy, first pull every time.

Yes, i could not see anything alarmin while overhauling the transmission.

Re: Clacking sound in rear tranny/variator

DrGeorgeTompson (Alan) /

> Kristian Lomeland Wrote:

> -------------------------------------------------------

> > DrGeorgeTompson (Alan) Wrote:

>

> > -------------------------------------------------------

>

> > Starter clutch?

>

> If they were bad, wouldn’t it be difficult to start? It starts super

> easy, first pull every time.

eh, if the springs are bad or weak the shoes can bounce off the clutch bell, but probably make it easier to start.

I assume since you rebuilt the gear box, that is good. so it kinda leaves the driven pulley/clutch bits. have you looked at the clutch itself yet, are the bearings in the rear pulley good? The euro clutches have really small posts, they could be bent but i doubt that.

Re: Clacking sound in rear tranny/variator

if u fat or skinny, subframe box has lotsa weak spots. oh wait its a nice si box. check for tightness on the rear mounting bolts i like to thread lock em. the output shaft shouldn't slidle in/out too much u got the 4 stars or was it changed out to spokes, spokes make that clacking sound, bad/loose wheel bearings more likely.

Re: Clacking sound in rear tranny/variator

> DrGeorgeTompson (Alan) Wrote:

> -------------------------------------------------------

> > Kristian Lomeland Wrote:

>

> > -------------------------------------------------------

>

> > > DrGeorgeTompson (Alan) Wrote:

>

> >

>

> > > -------------------------------------------------------

>

> >

>

> > > Starter clutch?

>

> >

>

> > If they were bad, wouldn’t it be difficult to start? It starts super

>

> > easy, first pull every time.

>

> eh, if the springs are bad or weak the shoes can bounce off the clutch

> bell, but probably make it easier to start.

>

> I assume since you rebuilt the gear box, that is good. so it kinda

> leaves the driven pulley/clutch bits. have you looked at the clutch

> itself yet, are the bearings in the rear pulley good? The euro clutches

> have really small posts, they could be bent but i doubt that.

I understand. The driven pulley and clutch in the rear is the only thing I have not replaced anything in. And therefore i have little knowledge about them. The previous owner said that is was some kind of bushing that was causing the clacking noise, but I dont know if that adds up? What bushing could he have been talking about if so?

I will look in to the clutches tonight. Do you have a good way of checking if the clutch springs are good or bad?

Re: Clacking sound in rear tranny/variator

DrGeorgeTompson (Alan) /

> Kristian Lomeland Wrote:

> -------------------------------------------------------

> The previous owner said that is was some kind of bushing

> that was causing the clacking noise, but I dont know if that adds up?

> What bushing could he have been talking about if so?

>

> I will look in to the clutches tonight. Do you have a good way of

> checking if the clutch springs are good or bad?

The only bushing that i can think of is in the outer driven pulley cheek that's closest to the clutch. It is the bushing that the movable cheek rides on. If the movable cheek has a lot of side to side play or wobble, you may need to investigate further. The cheek is under spring pressure so it may be hard to tell while it's assembled.

You can see the starter clutch springs inside the clutch bell check to see if they've stretched or broken. The starter shoes are held on with a big circlip or snap ring or whatever you want to call it and like a spring washer thing under it.

There are a few needle bearings inside the rear pulley assembly that ride on the input shaft of the gear box. Make sure those are greased and free.

Getting to the actual clutch is kind of a pain. you need to remove the big flat nut (i think it's 36mm?) on the rear pulley and the pulley cheeks shoot off and fly across the workspace. I use an electric impact wrench to remove the nut and keep pressure on it so the plates dont spring off. There should be a locking washer on it that you will need to bend down. tbh, i dont think you are having problems with the clutch and wont needto open it up, but who knows. You can usually see if something is bent while it is assembled.

Pat has a good point. make sure the inner pulley cheek isn't rubbing on the frame and that the mount bolts are tight. Loose bolts might explain why it only makes the noise with a load on it as the wheel is moving slightly under the tension. Also make sure the rear pulley cheeks are straight.

idk good luck!

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