Modern Vespa

Hi all. I have a 2010 LX50 2T. It was going great 6 years ago apart from the exhaust rusting out. I parked it and put a cover over it and kept it dry and that's until the other day I pulled it out put a new Sito plus exhaust and a malossi air filter and some fresh fuel and battery and she started straight away. I have removed the restrictions and she always went 65Kph. Now she feels like she wants to go faster but starts running a little rough at top end and going up hills then dies after 20mins. It won't start but for a while but the other day I took the cap off the fuel tank for a few seconds and put back on and she started but again after 5mins started to almost die again going up a hill. Anyone have any ideas ? Do I need a new larger jet with the air filter and exhaust ? But why does it just do this when hot. The auto choke seems to be fine. Many thanks in advance

If you changed out the air filter and exhaust, you usually need to upjet some. Pull the plug and post a pic on here.

Sounds to me like your eval system is plugged and its starving for fuel once a vacuum has built up. You could test this by leaving the gas cap loose on a partially empty tank and just ride it.

It doesn't sound like this at all. If you've made modifications to let more air through the system - which you have in a big way through both the intake and the exhaust - without changing the size or jetting of the carburetor, the engine is running lean and is stopping, or almost stopping, because it is getting hot and seizing. This is especially problematic with two-strokes, because the fuel itself significantly cools the cylinder. Stop running that engine and upjet!!!

Spark plug

Yeah, that plug is got way too much carbon and unburned oil built up on it. Install a new one. You may also want to post the plug make and number to make sure it is the right one.

Many thanks for your help everyone. So I have the scooter running nicely now. This is what I did. Replaced the spark plug with a NGK BR9EIX. Replaced both the fuel feed line and vacuum line. They were brittle and may have been restricting both the fuel and the vacuum. I upped the fuel jet from standard to 63. My LX50 doesn't go any faster with the new jet and exhaust. Still 65kph but I'm happy with that. Many thanks and I'll let you know if anything changes.

The Sito plus is basically a stock exhaust, despite what the people selling them will tell you, and a free flowing air filter isn't going to add horsepower either. You likely overjetted it, because neither of these things would necessitate the need for a new jet, so at the top it's choking on too much fuel. Even with a real performance exhaust, you usually don't need to rejet.

If the sluggishness and stalling at high speed have ended, ie, the symptoms of seizing have abated, then 90% of the battle here is won. Worst case, you're running a little rich. You can do that for a very long time. Give the engine a thorough test for a few days to make sure the seizing really isn't happening, then take a look at the plug to decide if you want to go back down in jet size. Maybe you'll get a few more mph out of it. If not, and the plug looks OK with the original jet…then I would ask, what's the point of deviating from the stock air filter?