Modern Vespa

Hi,

I've tuned my Vespa PX125E (VNX2T) with a Pinasco 177 kit. The carb is a Dell'orto SI 20/20 tuned like this: 45/140, 160/BE3/108, 5mm hole in the air filter, mixture screw is turned out 1 1/2 +1/8 out, idle screw was 2 1/2 out and then 1/2 in (something like this). Spark plug NGK BR9HS. Stock exhaust, and all the rest is stock.

I'm on break in period (first 500km) and having 4% oil mix ratio. Starts always without choke (ext. temp 8-10 celsius), when pull the choke revs drop so that's normal. When go off throtle and the speed is drop off (5-10km/h) starts a little bogging but I think that's normal, and is similar to car under revd in highear gear.

But the spark plug is really fouled as you can see in the picture (was clean by mine around the thread). THat is normal and I have to wait after first 500km when the mixture drops at 3% as Pinasco recommend or I can play with the mixture/idle screw and jetting? I'm affraid of seizeing it.

Unfortunately there is no one near me (300km radius) that knows how to set a vintage Vespa engine (thy know 2 stroke but...)

Tks

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Is the fouling actually causing the plug to fail?

If not I'd leave it alone until you've run it in and moved to the 3% premix which will richen it a little more. If it's still looking fouled you could then try a 106 main jet.

You could also go to a NGK BR8HS. It'll run a little hotter and help combat the fouling.

Is the #9 plug recommended by Pinasco? That seems on the too cold side. Try a #8 if possible.

I have installed Bosch w4ac when Ngkbr9 fail from fouling and look pretty clean after but feel that the engine get hot (ungortunately i don't know how to check when is normal or hot) . After break in period I will drive longer trips (around 200km) and afraid of seizing

So, how can I check if the engine is hot or normal hot? And what to do next?

Get yourself a CHT temperature gauge. They aren't expensive and it'll give you some confidence when your playing with your tuning. Outside air temp is irrelevant.

Are you running an autolube with 4% or a premix?

If its an autolube, thats too rich a mix.

I just chucked a capfull in with a tank of gas with autolube and running in a 225 sweet as.

You wont seize it if you checked your squish, timing, ring gap, slightly rich jet and dont have any air leaks. If you havnt done these things its not too late to do so.


What pipe are you running?

+1 on the b8 plug

Whats that grit looking stuff on the insulator?

Good ideea with the CHT, but what is the normal temp for this engines (tuned?). . No autolube, premix. Standard pipe.

Timing is ok (IT as Pinasco write on the install manual), ring gap check (0,25mm), first jet was 110, no air leakes, no squish check until now.

I'll wait until 3% and if the spark still fouling i go for a ngk br8hs.

The "grit" are remains from cleaning, nothing like metal, stone, and other destroied parts.

Do some research and a safe range can be from 100c to 200c (city, highway, hill, etc) mine is ok, I can put a finger on it after 5 km. Hope is correct

Today, again the spark plug fail from fouling. Vespa losing slowly hr power and then stop. I install a Bosch w4ac, now running fine. I will clean the carb again, recheck the flow, and thinking of decoke after first 1000km.

Try a hotter plug. Its probably the first/easiest/cheapest/likeliest thing you can do to improve things.
The 4% mix could also be something to do with it?!

Way too much oil!

It's the pipe, way to old. Less and leas smoke, bogging, loss of power and engine stop.

Cilinder head off, and ....

Need a new exhaust.

I've found some OEM pipe for px 125 on scooter center.de at a good price.

What do you know about them? I know that too cheap means too expensive in fact

Theyre fine if you need specialist parts in small quantities rather than SIP's min order qty, ive bought stuff from them as have others.

But what i cant fathom is why you dont take this as an oportunity to save up a bit more, do some research and get a decent pipe to go with your new kit dude

Yes I'm looking for a SIP Road or SITO+ but for now the budget is tight. Next upgrade will be a SI 24/24 and a pipe, need just for touring purposes.

I've tried to to clean with sodium hidroxide, not working, maybe just for a cleaning but no if it is clogged.

Tks for the help guys. I've bought the OEM, come back with pics on arrival to see the quality.

The exhasust is mounted. Quality is ok, but sounds like a shotgun
I've installed a B8HS and go down to 106 jet. Still the spark plug becomes sooty after 2-3km. Meanwhile, change the float needle, still the same: the spark plug becomes sooty and the scooter will stop and wont start....

Next thing, I'll go down to 3% mix, after that I really don't know what to do, and unfortunately around here there is no one to know about vintage Vespa and this SI carb.....

In 2nd and 3rd gear seems like boogind down a bit


Any other clues? What to check and where to look?

ps: clean the tank gap breather...same.