Modern Vespa

Issue #1
I seem to have lost top end speed , cant get to that 130 mark anymore .
Still have lots of power just wont go as fast as it used to .
I noticed over the last couple years I guess that the speed had dropped off .

Issue#2
Cutting out , This seems to have started since I had the engine out and put the bike back together .
When i get close to the 100 k/hr mark it bogs out , kind of hesitates , might even flash check engine light .
I just throttle on to get past it and then it is ok ,.
Happens pretty regularly .

2014 gts 300 super , 46,000 km
I recently had the engine out to remove a broken exhaust stud .
While it was out i did adjust the valves .
Other then that it has had all maintenance done as per the owners manual .

Looking at the manual , I think the only thing I have never done is clean the throttle body .

A possibility on the top end speed issue -- I've read here on MV that long running at a consistent high speed can wear a groove in your variator that then reduces top speed over time. There was discussion of this in the Cannonball thread.
here https://modernvespa.com/forum/post2470765#2470765
here https://modernvespa.com/forum/post2297582#2297582
and here https://modernvespa.com/forum/post2297582#2297582

Maybe?

I had your issue#2 with my 2015 GTS300 Super. At about 90-100 kph it would start missing, no backfiring or anything, just jerks in the power. If I opened the throttle fully it cleared and accelerated on. I tied everything to fix this, and ended up replacing the whole throttle/ECU body and that fixed it. An easy fix, but expensive. I think it is a throttle position sensor problem, but wouldn't have a clue how to tackle it.

I agree that issue #1 sounds like a grove groove in the variator. Two threads that describe something similar as your issue 2 are Another stalling GTS and Struggling to start - GTS300 Super.
Hope you get it sorted!

edited for spelling

Same issue on two 300's. Same cure. As he said it ain't cheap but fortunately mine were under warranty.

I have never had a problem like that on any of the five GTs I own or have owned over the years.

Old tech sometimes has it's advantages.

Bill

Agreed that #1 sounds like a worn variator. But it could actually be related to #2.

The #2 issue has a couple of possibilities. The most likely, IME, is fuel delivery. If your gas tank doesn't vent properly (a common problem if the evap system is still connected) then you can develop a slight vacuum in the gas tank, usually under high-fuel-consumption situations where a lot of fuel is being pumped out of the tank -- air needs to come into the tank to replace the volume of liquid that was pumped out.

The evap system is notorious for failing here and not allowing air to come into the tank. I don't recommend drilling a hole in the gas cap (as some people have done), but I *do* recommend removing the evap system. If that's a bridge too far, then at the very least temporarily remove the hose from the vent on the gas filler neck and see if that alleviates the problem. If not, you can probably cross this off your list and look for other causes.

My good friend Lostboater sent me a message to remind me of the money I have spent to keep my GTs on the road.

Maybe I got carried away, since the current three are running like new, at the moment.

Owning any Vespa model can be expensive.

But we didn't buy them to save money.

Bill

2008 called. They want their money back.

Explanation for those that have not seen MVs traffic stats: 2008 was the peak of traffic for MV, buoyed largely by US gas prices. There were other factors too, but the cost of gas definitely had a huge impact. So yes, many people did in fact buy a scooter to save money. The fact that it probably did not actually save money is secondary.

The topic has a possible funny twist. In fact, if someone on the web is looking for information on "problems with the couple relationship" understood as a relationship between two people, one of the pages that will open will be this one on Modern Vespa.

Heh. North Americans seem incapable of saying "A couple of". However, perversely, they say "off of" instead of just "off" or "from".

But then again, I can't understand half the UK dialects, despite having been born, bred and survived there for sixty years.

"English as she is spoke" I guess.

I'm not entirely sure some of those dialects even qualify as English.

True enough.