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Hiya.

My Vespa PX 125 is running ok, but is sputtering in 3rd gear at 20mph and 4th gear at 30mph. When i excellerate its fine and top end its good, but if i sit at a steady speed then it chugs/sputters.

Any ideas?

Meddy
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you are short shifting. wind out each gear almost fully before you shift.

a general guideline would be

0-15 first gear
15-30 second
30-40 third
40 and up fourth
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Yes to what JJ says because if you dont you will foul plugs like crazy and you could put yourself or others at risk while riding in traffic.
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i'm not short shifting, im using the full range of revs, but its when i hit a 30mph zone and im still in 3rd or a 40mph and im in 4th gear, it just seems to sputter like its misfiring/gonna die.
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I would check these

fuel delivery
clogged exhaust
clean carb
points gap
external coil

you can easily search on here for how to's for each of these.

how about some history of the recent work done on the bike. like when was the last time the carb was cleaned etc.
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like someone else mentioned, what else might have changed recently? new exhaust? something else?

if some mod had been done like putting sito+ on after having a stock exhaust, could be something like pilot mix screw, or the wrong mixer on the main stack.
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ok, so i'm setting off in the morning and the engine is cold and it hesitates especially in 2nd gear. This i can understand. But even after its warmed up and i'm sat doing a constant speed the engine kinda splutters/struggles until i open her up. She hesitates a little and then is fine when i wind her up. It seems that by going balls out its fine, but when setting off from slow speeds she hesitates/splutters.

Ok changes i've done. Its got a PM Tuning pipe on it and i was getting a little bit of pinking so i up jetted to a 103. Plug is a little black and the air filter is a little boggy.

I have also put a new HT lead (NGK) on it
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Whats a pm tuning pipe.

Is it one of those knock off wanna be expansion pipes?

You may just be experiancing normal flat spots until you are "on the pipe".

Make sense.
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jimmyb865 wrote:
Whats a pm tuning pipe.

Is it one of those knock off wanna be expansion pipes?

You may just be experiancing normal flat spots until you are "on the pipe".

Make sense.
PM pipes are one of the best pipe brands in the UK, original started as pipes for Lammy's.

http://www.pmtuning.co.uk/pm-tuning-evolution-chrome-expansion-chamber-vespa-px-125cc-180cc-6784
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Kasperwinding wrote:
PM pipes are one of the best pipe brands in the UK
Thanx Kasper....I know what a PM pipe is. It is one of the low level stamped pipes for expansion. But make no mistake. It is a 100 dollar range pipe. It is NOT a 500-600 dollar pipe.

Although it is worth mentioning that they do make a 500 dollar pipe for 4ts.

My comment is quite ironic. It is a knock off, offended or not, but it does provide the specs to give a tune at a certain rpm range, so..........that is why he may be expeariencing the sputter at low range because he has not gotten to expansion "on the pipe".

So even though it may be a cheap pipe it IS delivering the effect and MAY be what the PO is feeling.....irony

Make sense.
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Have PM tuning pipes on 3 of my bikes, great exhaust well made and definatley not a cheap pipe here in the UK.
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Billy Anthony wrote:
Have PM tuning pipes on 3 of my bikes, great exhaust well made and definatley not a cheap pipe here in the UK.
Okay Okay

Cheap is the wrong word. It is a good $100 range pipe.

We/I are getting away from my point.

Some of the hesitation that he/op MAY be expeariencing could be normal flat spots associated with expansion pipes. Better?
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Yes sounds like the jetting needs to be looked at.
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The part that I am trying to make a point of without offending anyone.
meddyuk wrote:
She hesitates a little and then is fine when i wind her up. It seems that by going balls out its fine, but when setting off from slow speeds she hesitates/splutters.

Ok changes i've done. Its got a PM Tuning pipe
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Just a question what pipe do you run on your lammie?
Few mates have lammies (GPs and LIs) they swear on PM pipes.
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Billy Anthony wrote:
Just a question what pipe do you run on your lammie?
Few mates have lammies (GPs and LIs) they swear on PM pipes.
I am currently running a cheap big bore clubman that is as annoying as all get out. But it does react well with my cheap Indian 187 top end. If you do the ports and set up right it shows some power from the larger down tube to box. It has a nice range but is not a pipe that hits a hot spot like an expansion pipe.

I run the piss out of this thing and recently did a 5000 elevation ride and it performend great. Annoyingly noisy like a loud bad steel drum band. Ask Vader

Now if I were to go BIG I woud probably find another JL righty for lammys. I had one on a p210 and it was the shit. Spendy though.
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My friend has a JL on his GP and he rates it while another friend had a JL on his P200 and thought it was terrible. That clubman pipe gives off a serious grunt..
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Billy Anthony wrote:
My friend has a JL on his GP and he rates it while another friend had a JL on his P200 and thought it was terrible. That clubman pipe gives off a serious grunt..
I would never put a high end pipe on a stock set up. Waste of serious money. Even a tuned p210 with a stockish pipe can be a lot of fun.

The gp 200 is a good motor for a big bore pipe so I guess a jl would be good. Don't know. Don't have a large block motor to play with, or a jl pipe layin around.
My small block is good right now for my budget. All those website mods for bikes is a very pricey rabbit hole that I cant do right now.

As for PM pipes, I have seen some badass small frame pipes by them.

Those look to be high end and pricey.

The Clubman is a great design but sound aweful. There have been some companys working with the performance big bore/stock design for Lambrettas. They are not cheap, very pricey.

I am not the guy to talk on and on about pipes for vespas and lammys. Vader and AGeofIndustry are the dudes.

Vader is running a stockish performance pipe on a. 25hp motor and has other pipe set ups on other bikes that are very pricey. AgeofIndustry has many Lammys with different pipes.
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i also read that having an expansion chamber on a stock bike can mean that its boggy and gets flat spots.....what does this mean and is this what im experiencing?

Btw the exhaust is this one

http://www.pmtuning.co.uk/pm-tuning-evolution-expansion-chamber-vespa-px-125cc-180cc-4343
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meddyuk wrote:
i also read that having an expansion chamber on a stock bike can mean that its boggy and gets flat spots.....what does this mean and is this what im experiencing?

Btw the exhaust is this one

http://www.pmtuning.co.uk/pm-tuning-evolution-expansion-chamber-vespa-px-125cc-180cc-4343
Its a nice pipe okay.

The pipe is not the issue.

The issue is you're feeling like your bike is acting weird at a certain range.


Have you tried putting the stock pipe back on to see if it changes anything?

You will no doubt have to take your jetting back to stock as well.

The point is if you start from there then you know where you're goin.

Make sense.

It could be a number of a few things but for me I like to know how it acts stock before I start adding shopping kart items.

Good luck.
⬆️    About 2 months elapsed    ⬇️
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Im having a similar issue on my p125x. I am running all stock. It sputters a little on cold starts in the morning on 1st and 2nd gear and then its ok when i ride it out. is this normal? what can I check?
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