GTS OWNERS CLUB

g-tease · Site Admin Joined: 14 May 2007 Posts: 361 Location: London

My GT is a bitch at the mo...been getting a low rumbling on pull away and not biting on accelation, well on the advice of one place I have changed variator, rollers and belt and it still does it?! The only thing I can think of now is that it might be the clutch???? does anyone have any ideas...any thoughts gratefully accepted as I ride it every day and I feel like I've lost a limb at the mo Sad

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

Surely they checked the clutch when diagnosing it was the variator at fault? If not then yes i would check it....

Firstly take the whole unit off and check the shoes for wear marks. As the shoes wear the "touching" part of the shoe will move along its length, so when new it will be on the outer edge and once worn it will move to the inner edge... once there its time to replace them. So check that.

Then give the whole unit a wash with a solvent cleaner like brake cleaner to ensure its all clean... then also wash the drum as well... youll often find a small amount of grease collects on the clutch drum which over time contaminates the shoes slightly, this is because the clutch pulleys bearings are greased but the unit doesnt have a proper mechanical oil seal fitted so the grease works its way out slightly.

Make sure the twistable pulley moves smoothly and freely.

Regrease the bearings and refit and see how you get on.

Did you use genuine rollers or pattern ones? Is it a genuine variator unit or performance item? Same with the belt.. genuine or pattern?

monty9120 · Posted: Fri Dec 28, 2007 10:49 pm Post subject:

i get alot of rumbling from mine but my clutch bearings are shot

dont know what to suggest with the no biting but it can be many more things if you have checked the variator etc
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g-tease · Site Admin Joined: 14 May 2007 Posts: 361 Location: London

Only used genuine parts and have not gone for any performance parts. Looks like the clutch is the next port of call then......thanks for the advice Wink

thpriest · Joined: 27 Oct 2007 Posts: 12

i'm beginning to get the same. in modernvespa they suggest openning the we 'vespa' cap on the motor and blasting it with compressed air to remove build up of dirt. others suggest the solvent like above.
i'm gonna try compressed air.
most speculate that it's due to driving at v slow speeds which happens a lot to as i drive in dense traffic
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g-tease · Site Admin Joined: 14 May 2007 Posts: 361 Location: London

slow speeds, yeah that'll be me then.....haha.......NOT! will try the air idea first, but then on to getting a new clutch if no joy!

MikeHolland · Posted: Wed Jan 02, 2008 10:24 pm Post subject:

At the moment my clutch is slipping on pull-off. May be the same problem. I am about to go over the clutch pads with a file to get rid of the glaze, and also examine the clutch bell. I believe this can also get a glaze which can be removed by honing it.

But I will also check the belt in case that is what is slipping!

Mike
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Vespa GTS250 Vintage Red

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

Chances are you will find a damp oil residue on the drum which has leached from the bearings.

MikeHolland · Posted: Thu Jan 03, 2008 8:24 am Post subject:

Treated the clutch pads and bell with a file and some emery, and problem solved.

But I discovered that my belt needs replacement - only 78mm wide!

Always something needs attention. I am beginning to hate the CVT transmission - the rollers develop flats, the belt wears or stretches or snaps (heaven forbid), the clutch gets dusty or its wotking surfaces get glazed. The clutch springs get slack with age.

After the first 15000km or so, a CVT is in a perpetual state of decay.

And the worst of it is you have to pull it all apart every so often to check it, as you have no outside indication of what is going wrong when, except for lousy performance.

Give me a good old gearbox, anyday.

Mike
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Vespa GTS250 Vintage Red

Maver · Posted: Thu Jan 03, 2008 9:50 pm Post subject:

MikeHolland · Posted: Thu Jan 03, 2008 10:26 pm Post subject:

Sorry, got the numbers right, just the units wrong. Belt width is 0.78 inches which is the middle of the recommended range - 0.8071 - 0.7600.

Mike
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Vespa GTS250 Vintage Red

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

The CVT system is quite decent at doing its job, yes bits and pieces wear but its so much smaller than a gearbox arrangement would be.

MikeHolland · Posted: Fri Jan 04, 2008 7:29 am Post subject:

Come again Cheeky?

It is nearly twice the size of a PX gearbox and nearly as big as a Lambretta chain drive and gearbox.

The PX gearbox just has two shafts - the cone-shaoped cluster gear driven by the clutch and the set of gears on the rear axle. All the works are inside the rear axle, except for cables and selector mechanism.

The GT/GTS drive train has clutch, variator, belt, belt tensioning pulley, intermediate gear shaft and rear axle. Twice as many turning shafts. More if you include the pulley.

And all you do on a PX gearbox is change the oil once in a blue moon. Once in the lifetime of the scooter you change the gear selector cross, and once every 30,000 km or so you replace a gear cable. If you grease the cables when fitting, they last for ages. My record for changing the gear selector cross in a GS150 is 4 hours.

Am I shedding light on the dark side of the Dark Side??

Mike
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Vespa GTS250 Vintage Red

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

But the PX gearbox is proper old school and people wouldnt accept it on a modern scooter due to the hop skip jump from neutral and the way the clutch lever moves so much in use...

Then you get the fact the PX has to have regular cable adjustment, the fact the clutch units aint very strong... and then the way the selectors wear... old technology.

I think the belt system is very compact, final drive is a tiny box and practically maintanence free, how many shafts do you think the GTS has? Variator is on the Crank, Clutch is on the intermediate shaft and drives the rear wheel shaft, not exactly overloaded with them is it. The system looks big as its long, but its long and thin VS the PX's more square engine shape.

If i had to choose between having a notchy PX box or the GTS's belt system i know which i would chose without battering an eyelid.

MikeHolland · Posted: Fri Jan 04, 2008 10:19 pm Post subject:

Count again, Cheeky. There is another gear shaft between the clutch shaft and the rear axle.

The PX gearbox may be old technology, but it has been refined over 60 years and there is little on the road as reliable as a PX.

OK, so I remember the many times I pulled off fast in 1st, crash-changed through to 2nd - and landed up in 3rd to my embarrasment!

But then it is so easy to adjust the cables. On a PX you never have to replace rollers, replace a rubber belt, or pull the transmission open just to check these items (15 screws and bolts, 2 highly torqued nuts). Consider the difference in effort between replacing PX clutch plates and replacing GTS clutch pads!

Yes, the CVT system is lovely for riding. It is the maintenance that I am complaining about. But then it is new technology, and no doubt has a lot of refinement ahead of it.

Mike
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Vespa GTS250 Vintage Red