OP
@cr1st1turc1n avatar
UTC

Member
GTS 300 HPE SS, PX150E, MotoVespa 150S
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Location: Romania
 
Member
@cr1st1turc1n avatar
GTS 300 HPE SS, PX150E, MotoVespa 150S
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Location: Romania
UTC quote
Hi,

I have a headache about the handling of my PX150 front disc brake.

After 1000km on somehow bad road in Balkans (Romania, Bulgaria Serbia) riding is very squirrelly. The front of the bike is going from left to and and bag, didn't go straight line but a little bit in zig zag. After all the talking, looking and feeling, I've done this:
    change the front shockabsorber (old one but better than the existing one)
    change all the front hib bearings
    check fork bearings (ok)
    retight the fork
    chnage the front tire/rim with back, with another (old one but looking straight) and back tire/rim
    change the silent blocks from swing arm. starting to feel more tight on the back and a little in front.
    adjusting tyre pressure within specs and even a little low.
    check the rubber buffer rear (not torn or damaged but a little soft
A little better after the silent block change but still squirrelly in straight line and not following a straight line in curves.

Before this trips was feeling rock solid and a tight bike, and played a lot with it, like riding with one hand and bypassing potholes with easy...feels very straight.


Other riders try it for the first time and feel the same: gliding from left to right and back most of the time....


What to check and look for, anymore??

Tks
UTC

Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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UTC quote
bent rim? bent fork? bent axle? steering bearings? are they tight enough?
@glscoot avatar
UTC

Molto Verboso
Vespa GS150, Messerschmitt GS150
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Molto Verboso
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UTC quote
put scooter on stand and grab back of tyre & rim, try moving it from side to side, if the hub moves with the rim, its more than likely the hub. check both but probably the rear.
UTC

Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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UTC quote
yes - definitely check the rear as a loose hub via either a loose nut/bolt, bad hub or bearing can manifest as front end wobble or weirdness.
@astromags avatar
UTC

Veni, Vidi, Posti
'80 P200E, '76 Primavera 125 ET3. '59 Vespa 150
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Veni, Vidi, Posti
@astromags avatar
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UTC quote
A broken rear shock mount can make it feel squirrelly, as well.
@subetherbass avatar
UTC

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1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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@subetherbass avatar
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UTC quote
Bolt just under headset it loose, or at least not tight.
Hold wheel between knees, & see if you can turn the handlebars, if so things are loose... Mine used to do this all the time, even though the bolt appeared tight
UTC

Molto Verboso
px200
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Molto Verboso
px200
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UTC quote
Hello

If the head races are overtight the bike will have a pronounced slow speed roll, you may have a notch or dent in the head race.


Grumpy
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
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Mr. Clean
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UTC quote
Grumpy wrote:
Hello

If the head races are overtight the bike will have a pronounced slow speed roll, you may have a notch or dent in the head race.


Grumpy
This is what I was going to say, but don't know how it would have overtightened while riding.. ? can that happen Grumpy? with the locking ring in place?

I've ridden with the top ring over tightened and it's horrible and feels just like what he's describing.
@socalguy avatar
UTC

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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bodgemaster
@socalguy avatar
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
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UTC quote
Second what almogavar said. Loose rear hub nut and/or rim nuts will cause bike to wander and make steering feel vague and weird.
@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
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Veni, Vidi, Posti
@ginch avatar
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UTC quote
If the tyres are worn in the middle, it can affect how it feels when riding anything other than straight roads.
OP
@cr1st1turc1n avatar
UTC

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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
Ok.

head races not overtight, not loose (no play in the fork), a little bit losse, cause the bike is somehow follow the road (bumps, inclination, etc)
no play at the front hub, all bearing changed. grabbed and moved, all ok front
back hub: bearing changed, hub tight, little play (same as other pxs)
rear shock absorber mount: lower changed>new, upper, not changed a little soft as i moved the shock absorber without engine mount.


again, maybe i don't describe very whell.


The front of Vespa just "slides" from left to right, and right to left. no play, wobble, overtight. is like having a very worn out tyre or running on ice. not going on a straight line but making "eights" not much but enough not to feel confident in our riding.

straight line high speed is somehow ok, but around 40-50 km/h start to glide/slide a little....

ride alot of other largeframes..but this nothing like this before...
@subetherbass avatar
UTC

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1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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@subetherbass avatar
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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UTC quote
are they (4-ply) wheelbarrow tyres by any chance?
I ran with them for a few years, & it used to do great drifts around corners once they warmed up!
⚠️ Last edited by SubEtherBASS on UTC; edited 1 time
@bobo avatar
UTC

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'70 Super 150, Medley 150S, '23 Ducati Monster SP
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@bobo avatar
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UTC quote
My guess is your front wheel is buckled.
UTC

Molto Verboso
px200
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Molto Verboso
px200
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UTC quote
Hello

They tend not to over tighten when riding, but they can dry out, then it appears as if they are tight, the OP did say he had been over some road surfaces, my guess there is a notch in the upper race and that is easily felt with the bike on the stand, worth checking if the tyres are on the right way round.

Grumpy
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UTC

Hooked
2012 Stella
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Hooked
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UTC quote
could be as simple as tire (tyre) mix...sounds a lot like the 'ice skating' effect I had with the old heavy cruiser I had (Honda 1100 ace), front end felt like it wanted to 'slide out' and turns felt like I was riding a trout...

turned out to be mixed brand tires/tyres, Dunlop in front, Meltzer rear...swopped out the Dunlop and problem cured.

a little research told me every maker uses their own 'blends' so sidewall stiffness, 'road stickiness', etc give often incompatible characteristics.


Nerd emoticon just saying...
OP
@cr1st1turc1n avatar
UTC

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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
Grumpy wrote:
Hello

They tend not to over tighten when riding, but they can dry out, then it appears as if they are tight, the OP did say he had been over some road surfaces, my guess there is a notch in the upper race and that is easily felt with the bike on the stand, worth checking if the tyres are on the right way round.

Grumpy
Don't realy understand about "notch on upper race"??



About tyres: Michelin S1 front (2014, 4000 km) and rear (2015, 2000km), look allright, feel ok. Rims mounted on correct side.

Today ride, concentrating more on the bike: feeling like a bicycle with a rim like and "8", so the bike is moved slightly at an average speed from side to side. So I will look more closely to the back: rear hub, drum, rubber buffer upper...



Riding is somehow on the safe side but still not following a line on curves...
@subetherbass avatar
UTC

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1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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@subetherbass avatar
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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UTC quote
Riding is somehow on the safe side but still not following a line on curves...

This happens when you have done a lot of city riding, tread goes flat in th muddle, with a lip each side, when you lean the bike on country windy roads the bike seems to either want to go straight (scary uvdersteer) or feels like it wants to low-side.
Change the rear & problem goes away... I found this out recently while on th track.
OP
@cr1st1turc1n avatar
UTC

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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
SubEtherBASS wrote:
Riding is somehow on the safe side but still not following a line on curves...

This happens when you have done a lot of city riding, tread goes flat in th muddle, with a lip each side, when you lean the bike on country windy roads the bike seems to either want to go straight (scary uvdersteer) or feels like it wants to low-side.
Change the rear & problem goes away... I found this out recently while on th track.
Yes, I do 30km avg/day city ride in a city with, holes, bumps, bad sewer in the road, etc...


I will also try this, change rim&tyre with new.... but i don't feel that is only this



I've done, by mistake, the following test: Stop the engine at work in underground parking with epoxy surface and without the engine vibrations and going straight it feels in the handlebar like something slightly pushing from side to side....
UTC

Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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Molto Verboso
Lambretta GP200, Vespa P200e, Motovespa do Brasil PX200E
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UTC quote
man..im gonna say a bent rim. Especially if you say lots of potholes in city.
@astromags avatar
UTC

Veni, Vidi, Posti
'80 P200E, '76 Primavera 125 ET3. '59 Vespa 150
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@astromags avatar
'80 P200E, '76 Primavera 125 ET3. '59 Vespa 150
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UTC quote
Long Shot
Not sure if this would cause your condition, but worth a look I suppose.

Is the front tire installed correctly? Some can be installed with the tread in the wrong direction.
OP
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UTC

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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
Re: Long Shot
astromags wrote:
Not sure if this would cause your condition, but worth a look I suppose.

Is the front tire installed correctly? Some can be installed with the tread in the wrong direction.
yes. tyres are installed correct.

I will try with a rim and tyre fron a diff vespa. Its strange because I've ride it 1600km to vwd 2015 and the ride was flawless, smooth and without a single problem. After another ride to Nis/Serbia, aprox 1000km start doing this

I ride it everyday and now is not like it was and ride are not anymore enjoyable
@primavera130 avatar
UTC

Hooked
Vespa P200, Primavera 130, VNA200, Italjet Pack-a-Way Moped, Ciao etc
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Hooked
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UTC quote
almogavar1969 wrote:
man..im gonna say a bent rim. Especially if you say lots of potholes in city.
Me too.

I chased this for weeks on my VNA/P200 combo. tried a new fork, new fork bearings new tires.

It was a bent rear rim. Just barely bent.

It was causing one point on the wheel to be wider than the opposite point.

Exactly as the OP describes: under 40 mph felt like it was weaving, over 40-45 it would feel more stable.

I know you've replaced and swapped wheels, but it's worth a try. Switch with a friend or get a new set.
OP
@cr1st1turc1n avatar
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GTS 300 HPE SS, PX150E, MotoVespa 150S
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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
Changed front with rear, rear with other one. same

Nexte step, I will change both same time with other ones (old). Something should change anyway..

keep you updated
UTC

Molto Verboso
px200
Joined: UTC
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Location: london
 
Molto Verboso
px200
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UTC quote
Hello

Are the S1 new, the latest ones have marginal handling and in the wet it feels like you are going to fall off at any time.

Grumpy
@sara_alexandra avatar
UTC

Hooked
PX232 Lambretta li s3, Vespa cross, Vespa cross prototype, Honda NS400r....
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Hooked
@sara_alexandra avatar
PX232 Lambretta li s3, Vespa cross, Vespa cross prototype, Honda NS400r....
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UTC quote
check alignement between front and rear wheel. Could be you have bent frame or fork.
UTC

Molto Verboso
px200
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Location: london
 
Molto Verboso
px200
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UTC quote
Any further forward on this.

Grumpy
OP
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GTS 300 HPE SS, PX150E, MotoVespa 150S
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UTC quote
Yesterday changed rear shock and upper buffer. So now, all buffers on the engine and shock absorber are new. Retight front fork, inspect closely the upper bearing and nuts, so the bike feels more solid but.... same zig zag. It feels more precise zig zag, probably before all the loose bush and rear shock take all the shaking...


I will move to rear drum brake and hub. First to replace the rear drum to see what's happening. The hub have some axial play, but is the same when the season begings and ride 2500 on long runs and the ride was smooth...

I'll update
UTC

Molto Verboso
px200
Joined: UTC
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Location: london
 
Molto Verboso
px200
Joined: UTC
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Location: london
UTC quote
Hello

It really sounds if the steering races are too tight, or there is a notch/dent in one of the races.

Grumpy


Good luck with this.
⬆️    About 2 years elapsed    ⬇️
OP
@cr1st1turc1n avatar
UTC

Member
GTS 300 HPE SS, PX150E, MotoVespa 150S
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@cr1st1turc1n avatar
GTS 300 HPE SS, PX150E, MotoVespa 150S
Joined: UTC
Posts: 47
Location: Romania
UTC quote
Big problems, simple solutions...but you need to do the effort to look in depth.

It was the lower bearing on the steering head. Bent on all balls of him, because of potholes, I presume. Changed this and ...we have a straight liner.

A lesson for the future.
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@jimvanmorrissey avatar
UTC

Addicted
Vespa PX200
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Location: Belgrade
 
Addicted
@jimvanmorrissey avatar
Vespa PX200
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UTC quote
Hey Cristi! Glad to hear you got that sorted.
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