Modern Vespa

Dear Fellow Vespa Owners,

I have been happily driving my 2011 Vespa GTS 300 for more than 10 years with zero issues until about a month ago, when all of the sudden after coming from a long vacation it became hard to start and finally stalled on the road, and would not start, leaving me stranded.

After opening the air filter cover, I am ashamed to admit that I had never opened the air filter cover, the filter had disintegrated and was long gone. At that point I realized that I had been a bad owner and had to do a full maintenance job to the bike that had given it so much joy. By the way, the Vespa has around 14.5k miles and I bought it on 2013 with around 10.5k. During this time, I change the oil and filter every year and the transmission fluid once.

Anyways, I replaced the air filter, spark plug, spark plug wire, changed the oil and filter, new variator and belt, removed the EVAP system and cleaned the fuel injector and the throttle body a couple times.

The bike now regularly stalls at idle, including sometimes while waiting at traffic lights, also there is hesitation when accelerating briskly and a loss of power at wide open throttle. It works fine once you come out of idle if you accelerate smoothly.

I am trying to avoid the part replacing game and unfortunately the closest dealership to me, Charleston, SC, is 2 hours away in Savannah, GA.

It seems to me that I may have a bad injector or issues with the ECU, the Vespa rides quite nicely when it is not stalling or losing power.

Please help and you in advance!

PS: I am normally pretty good with vehicle maintenance and I promised to keep up with the manual's maintenance schedule moving forward.

I think it's more likely that there is some crap from the disintegrated air filter in the throttle bypass. If you are feeling especially energetic, you may want to remove the throttle body and spark plug. Then run a bore scope down in the spark hole and the intake.

I've heard that if the seal between the two halves of the airbox is not sealing then it causes such issues.

could also be that the joins at each end of the throttle body are leaking air from when you reinstalled it

and did you mess witgh the adjustment of the throttle cable?

Thank you Tierney! I have not been too worry about the disintegrated air filter since I heard Robot from ScooterWest on a video mentioning that if this happens it will just burn on the engine. I am going to go ahead and remove the throttle again, give it a good clean and inspect it more carefully, checking for play on the butterfly shaft.

Thank you SteelBytes! I have been re-reading some of your post regarding your issues with the throttle body and it has inspired me to get it out of the bike again and take my time cleaning and inspecting it.

I will also be checking for air leaks on the throttle body connections and will try to use some starting fluid to test.

You are right that the air box may not be sealing correctly, I did not realize that could also be causing issues.

The bike has not thrown any codes, and it does appear that it is something I did that is causing the current issues with stalling on idle and hesitation when accelerating briskly or wide open throttle.

Coincidentally when i was reassembling my scoot six months ago after replacing the head gasket, the short black hose between the throttle body and the intake manifold cracked and needed replacing.

Problem solved! After disassembling the throttle body and cleaning it a few times and chasing air links in the connections, it got a little better but it will still stalled on idle and had some hesitation when accelerating briskly. Today I replaced the fuel injector and things did not improved but then I tried a new Iridium plug I had bought "just in case" and the Vespa started working perfectly.

I had replaced the spark plug with a new original, taken it out and inspected it once and tighten it further another time in case that was the issue. At this point I do not know if I installed a new defective plug or I did not installed correctly, but I am happy the scooter is back better than ever!

Now that it finally runs well, I am going to flash the brake fluid, install new brake pads and proceed with a much needed front and maybe rear suspension upgrade.

Thank you SteelBytes and Tierney for your help!

Perhaps you hadn't torqued the spark plug sufficiently and it had worked lose. Congratulations anyway in solving the issue.