Modern Vespa

I have just checked the tyre pressures on my GT. As I haven't had it for long, I stupidly assumed the service carried out prior to delivery would have involved checking them also.
As I've grown more comfortable with the scooter I felt that the front end wasn't as "robust" as I would of expected, turns out the pressure was about 1.2 bar! The rear was also quite low.
Now that I have set them at the factory recommended levels ( 1.8 bar front, 2 bar rear), I have encountered a shudder through the drive train on take off. It is only mommentary and doesn't effect the ride, however, I'm concerned that either the pressure in the rear is actually too high or coincidentally something else is the matter.
Any thoughts?

I'm very particular about by bikes' tire pressures and noted that they were actually reversed (front to rear) at the time I picked up my scooter at the dealer! When I brought it in the the initial service, they gave it once-around the-block and noted that "man, your scoot handles great - what tire pressures are you using?"

Regarding your question though - if your tire pressures are correctly set there won't be any ramifications regarding a shudder in the drive-train at take-off. My GT runs great at take-off.

Anyone with some other ideas regarding Mark's observations?

Thanks, Cactus. I should add that after setting the pressures correctly, the scooter handles much better and not suprisingly the front end feels so much more confidence inspiring, particularly under brakes! Cheers, Mark

Well.
The GT has two great flaws. One, the front end "wobbles" at 15-20 mph if you let it and, two, the machine SHUDDERS when the clutch engages.
This drove me nuts when I bought mine ( used ). After an internet search I was simply amazed at how many people reported this problem. And more amazed that nobody, especially Piaggio, had a definitive answer. I'm also baffled by those who don't have the problem.

I've done some experimenting and a lot of research. I think the answer for those of us afflicted is: Dust in the clutch housing.

Why do I think that? Because I can pull off that plastic chrom-ey VESPA cover on the CVT housing, blast 90 PSI air through the holes and the problem completely disappears for a day to a week. The first time I did this a dark grey cloud came out. Yes I was wearing eye and lung protection.
Some people ( who don't have a shop compressor? ) remove the CVT cover completely ( a 10-20 minute job ) and clean inside there with scotch-brights, brushes, rags, etc. Their symptoms go away for some time also.
A couple weeks ago somebody sent me a step-by-step for removing the housing if you're interested. The shop manual really doesn't help. It should be findable with a search.

I'm still at a loss for why some owners DON'T have this problem. I've heard on this forum that the GTS doesn't suffer from the shudder, so I assume Piaggio fixed it. But as much as I love my Vespa, I'm pretty cynical about the Piaggio company's honesty and customer service. It would be nice to find a cure ( different clutch plate material? different variator belt material? Maybe there's just some variance in clutch spring tension? ). And it would endear me to the parent company if they told us what they did in the GTS to make it go away.
If anybody finds a cure let me know. Meanwhile, drop a line to the forum if the dust cleaning works for you.


Russ in Mountain View

Cheers Russ,
What do you think of the coincidence of increasing the rear tyre pressure with the appearance of the shudder?
Mark

My gts has this shudder. But not always. It comes and goes, as also the acceleration varies. One day the vespa performs just okay, the next day it astounds me. Maybe a connection. Still trying to figure it out.
The first time I noticed this type of shudder on any vehicle was on a new Toyota Previa when I used to be in the car business. It was obvious and they all had it at the time.

Thomas

The shudder and rear tire pressure is probably coincidental. I only notice the shudder on my GT when I've been doing a lot of stop and go city riding. After I've been on a rural ride at 55-60 mph, it apparently blows the dust out, and the shudder disappears until the next time I ride in the city. I keep 29.5 lbs air in my rear tire, and 26 in the front.

Hi all - I currently drive an X9 500ie - which I am in the process of selling to replace very soon with a shiny new GTS. The X9 is also prone to the shudders - sometimes - but I always associate this with the clutch running too hot. It never happens on open road running, but is prone to happen doing stop/crawl in heavy traffic, on a hot day, with a passenger

Testing a new GTS recently I was amazed by its sprightly performance - and the smoothness of the power pickup in traffic. Seems just the job for my cross-London daily commute 8)

Nick

PS - This is a great forum btw - very pleased I found it!

Just like brake pads, the clutch shoes will creat dust as they wear, the dust builds up in the clutch bell, although not alot, it does seem to cause the clutch to slip and shudder until it grabs solidly. You can use compressed air to help blow out the dust, and most of the time a good ride at speed will clear it too.

I honestly think this is coincidence. The shudder problem on the GT200 is now pretty well-known, and dust seems to be the prime culprit.

I probably concur. Either the tire pressure is a coincidence, OR...it has changed the load on the clutch mechanism enough to change things.

I appreciate the notion that a fast trip might be dusting out the clutch housing. It hadn't occured to me, but it makes sense. I can't picture the mechanism ( will go in there next week when I have time ) yet, so I am not yet an authority.

I also guess that heat could confound things by changing the coeffecient of friction all around, though I would think crankcase/clutch housing temp is held fairly constant by the fine cooling system?

I also confirmation by you all. While the problem is well-known, I hadn't gotten the notion the dust-in-the-housing a consensus.

If anybody can shed some further light on this, please do. If somebody from Mars discovers this in the archives a few years from now, let us know if YOUR GT200 shudders.

Russ

Sorry about the typos above. My draft was perfect, so apparently there's a shudder in the website.
russ

i've done 1200km on my gt now. it started shuddering at about 800km but i thought it would be normal 'getting worn in' issues that would be fixed at the first service. i just had the first service and i told the mechanic and he just said, 'yeah, they do that.' in other words...get used to it.

i'm thinking that changing the piaggio clutch and bell with a malossi clutch and bell would eliminate this shudder problem.

can anyone with a malossi (or polini) clutch verify this? does it help?

I had this problem with my ET4 when I first got it 5 years ago.
Dust in the bell, quite a lot.
The ET has an air intake into the transmission housing, I found that mine was 'off'.
Like, hanging there, it also has exhaust holes underneath at the back.
I reconnected it, after removing the transmission housing, blowing dust, scotch briting the bell et al and haven't had
a problem since, remembering to reconnect it after variator maintenance and cinching it down with a cable tie.
I wonder if some GT's have a blockage of some sort, either in or out, that is causing a dust build up?
Manufacturing tape, twisted hoses, I dunno just guessing, maybe something up front or underneath the floorboard (where the et hose comes from)...?

Well the previous posters are correct, there is accumulation of clutch shoe dust and the linings appeared to be fine. I sand papered the clutch linings, and the clutch drum in a circular motion to remove the shine from the contact surfaces. I then washed all the friction surfaces down with Brake Kleen, using compressed air to blow the places out I could not reach, but not into the drive pulley/variator/belt area (do not want to flush lube coating off sleeve bearing in there or roller bearing in housing. To disassemble, I use an impact wrench (low #1 setting), but used the proper tools to use a torque wrench when reassembling to save time. Problem should be solved for another few 1000 miles.

Now for the root cause, I noticed the air scoop plastic housing has two phil screws and found the sponge air filter was clogged with dirt (previous owner never cleaned it), so no air flow into the variator belt area to help blow things out a bit...there are small weep holes shrouded in the housing for fluids...but that may have been the cause of the dust settling in there, only time will tell but I will remember to clean that small filter and clutch bell housing with compressed air and maybe use the Brake Kleen drill.

The air intake is intended for cooling the transmission area; it won't blow the dust out. The dust problem is just something that is endemic to belt-drive CVT transmissions and centrifugal clutches... you learn to live with it and blow out the dust from time to time. Keeping the air intake filter clean will help keep the clutch cool, though, and may prevent or delay glazing of the pads and bell.

Hello, quick question:
How does one blow out the dust? Just pry off the round plastic cover with Vespa writtten on it and hit it with an air compressor?
I would take the clutch cover off but do not have the clutch holder tool I saw specified for this. Is it really needed?
Thanks!
Roadie

It's much easier with a clutch holding tool made for the job. You can make one from a U-bolt...

Well done Jim, I sprung for the $16 "special" tool before I saw this post...

As for removal, you can use an air tool like an Impact Wrench on low setting, for quick disassembly (probably work for the Variator nut removal as well, if you use bungee to lock brakes). But you will need tools to properly torque the nuts when assembling.

Compressed air method, followed by Brakleen without removing cover and just spraying in the tiny holes is good enough for temporary fix (maybe 1000 miles) from my experience. Full removal of cover, roughing up the contact surfaces, blow out with compressed air (use a mask and eye protection) followed by Brakleen, again on the contact surfaces only, (don't get it on the cover bearings, painted surfaces and such) and you will be golden. 8)

Sweet, thanks for the responses, good to go now.
I did the air compressor blast and the shuddering is almost all gone. My wife doesn't even notice it but I'm a bit heavier so it does it for me.
Will make up a clutch holding tool and do the full scruff and clean soon.
Gracias.
Roadie