Modern Vespa

Hey guys,

I've been dealing with an issue over the last few weeks; ever since I moved about 3 hours north to Northern Seattle. Sad part is, its scooter season and shops aren't even taking appointments for another couple weeks. Anyways, I would appreciate any feed back, forgive the long post--

I had the bike in the back of a U-Haul, strapped down. When I arrived at my new home and whipped the back open, my scooter was suspended in the air, as if I were taking a left hand turn. Fortunately, how I had the straps wrapped around the bike prevented it from hitting the ground at any point, so zero aesthetic damage done. I'm pretty sure it took a few jostles, maybe something rattled loose because of this-

I had a major service done (9,000 mile major service) 2-3 weeks before I moved by the local authorized Vespa dealer, and the thing was running like a charm. I had never had any mechanical issues with the bike in the previous year I owned it, and I rode the hell out of it.

The problem: I start the bike. It is idling a bit rough. Give it some gas and it struggles a bit, then lurches forward, like it slipped gears (maybe 1st to 2nd gear, or 2nd to 3rd). From there it drives just fine; until I come to a complete stop or slow way down for a corner, then it happens all over. The severity of the "lurch forward" varies, some times its hardly noticeable (as has been the case the last 2 days), other times it feels like something may fall out the bottom of the bike.

This is the problem in a nutshell. What is making it hard to figure out is that it gets better or worse, seemingly at random, but more-so when the bike / weather is warmer. Its not as bad first thing in the morning.

The week I got up here I rode it to the authorized Vespa dealer where I currently live, about an hour away, and they took 30 minutes to check it out real fast. They weren't able to replicate the problem, but they took out an air filter and it was super dirty, and they also said the transmission case (the circular, removable door with Vespa printed on it) was dirty and they cleaned it out. There was a belt changed when I had the 9,000 mile service, and the mechanic hypothesized that the bike heated way up (due to the air blockage), and expanded that new belt, causing some issues. I got back on it and rode home after; and it was still doing it.

I had a phone conversation with the mechanic back home and he thought it sounded like an electrical issue. He was nice enough to walk me through what he would check out. I'm not mechanically inclined, and realized after our conversation that I was looking at a connection with a black rubber elbow fitting and a green plastic case that was NOT the spark plug. Imagine looking down on the motor, the spark plug, I learned, is more on the side/underneath than directly on top and just to the side a bit. If this is hard to follow, I apologize, as its somewhat challenging to type out. This is significant because the mechanic instructed me to "push down on the top of the black rubber fitted-elbow", as he and I thought I was pressing down on the spark plug to make it "click" into the correct position. As you can guess, it didn't click (it was not the spark plug I was pressing down upon), but it honestly made the lurching forward issue better; if not for just that ride. Its totally weird. Whatever I was messing with there seemed to put a band-aid on the issue.

This has made it hard to diagnose. I got desperate and took it to a Honda power sport store, they had a mechanic (who used to work on scooters) drive it around and I'm not confident he was able to replicate the problem, I was outside with him as he test rode it. He thought the rollers needed to be greased, or sanded down, and thats why it felt like I wasnt getting much power when accelerating. That was the "problem" that he noticed when driving it.

Basically, I'm chasing a phantom problem, and no one up here can touch the bike for a couple weeks. I just started a new job and this is my transportation, you can see why its been challenging.

If I can provide any more clarity, please ask, and thank you for making it this far. Hoping for the best-

Thanks-

Have to you checked to see if the spark plug is seated correctly? Might of come loose on the trip. Shot in the dark. Good luck. Sucks when problems occur. Maybe it's homesick. If you have time tell us what the problem was/is.

The mechanic felt the spark plug and didn't think it was loose; I haven't taken it apart and put it back in, though. Maybe this afternoon, I'm somewhat hesitant as I haven't worked on it before at all. Sure there are youtube videos out there-- If and when I figure it out (hopefully today by some scooter genius'), I will certainly let you all know.

I'll take a wild guess and say that when the belt was replaced it was not loose in the variator when the variator nut was tightened causing the variator to be loose. This may account for the slipping.

Hi,
It is possible and would display all the symptoms you describe if one of the rollers flipped in the variator whilst the belt was slack with the scooter on its side.
It's a suggestion as i would question an electrical fault, as such faults usually manifest themselves with an easy diagnosis.
Also have you checked your airfilter for fuel and oil ingress?.
Cheers Andy

if variator primary was correctly installed then replace the clutch drum.