Modern Vespa

First time posting

I'm having an issue with my 2005 ET4 with 8k miles on it. I was driving along and it suddenly had a loss of power and would not accelerate. I had to nurse it back home (thankfully it was downhill most of the way because I can barely get this thing to move).

It starts and idles perfectly fine but when I try to give it throttle it falls flat on it's face and will die. I am stumped as to what may be causing this.

Here is what has been done so far:

--Gas tank has been completely emptied and filled with fresh 91 (thought I may have gotten some bad gas).

--Changed the spark plug with brand new one.

--Cleaned and inspected the Carb removing all jets and making it look new again .....4 times so far

--Tried running it with the Brown key and the same thing happens. I also reprogrammed the Blue key and it runs the exact same way. The security light flashes when the key is off. Once the key is turned on it flashes once for 0.7 seconds then goes off and stays off.

--Unplugged every electrical connector and reconnected them.

--Checked all of the fuses.

--I bypassed the fuel tap with a gravity bottle full of gas.

--Cleaned the not very dirty Air Filter.

--Removed the muffler to test if the exhaust was plugged.

All of the tests above have resulted in NO CHANGE in the way the scooter runs. It still will not rev up past around 1500-2000 RPM. It idles perfectly fine and will probably idle all day long. I am going crazy over here trying to figure what the heck could be wrong with this baby !!!

Any help would be greatly appreciated.

man, that's always aggravating when you reach your wits end after trying everything several times!

anyway, seeing that you've gone thru the carb several times and the onset of the problem was sudden i'm gonna throw in a guess that the CDI went south.

sometimes, you'll get the correct flash code in the dash, but the unit is not operating properly. i've had two in the last month do the exact same thing--one being a ET4 with about 4K on it and the other a GT200 with well over that. both presented the exact same way, no notice at all. just bang, right into limp mode.

the easiest way to tell is to replace it with a known good unit and see if the problem persists.

best,
-greasy

Carb diaphragm cracked/compromised?

That could do it...

Maybe.

R

That would be my guess too.

...but that would have been spotted with the carb clean (*4).

Check the CDI by substitution, if you have a friend or friendly dealer who will allow a temporary swap.

I inspected them throughly when the carb was out and I did not see any problems with them.

I will see if I can get my hands on a local CDI unit or as a last resort see if the Dealer can work with me on testing one.

I appreciate all the feedback.

Thanks,

8)

where are you located?

i have a tester CDI, antenna & key set that i'll loan out if you're local.

shoot, if you bring the bike to me i'll test it while you wait.

-g

i eliminated the diaphragm on three counts: one, that there was already a carb tear down and inspection; two, a torn diaphragm will start, idle and run-- albeit poorly; three, the problem came on suddenly.

-g

My initial thought was carb diaphragm not sealed properly...I use a spot of white grease on the seal before I click it into place.....not sure it would come loose though unless the diaphragm became holed/tore...

Thank you so much for the help.

I would love to bring it by so we can try that CDI swap.

Shoot me a PM and we can setup the details.

Thanks Greasy !!!

So what was the issue. CDI? I'm in a similar situation...

I would like to know how this was resolved too. It is showing the symptoms of an un-coded cdi. The GT 200 service manual mentions that the service key can lose the data stored on it and if this happens to check the shielding of the high voltage system.

If you haven't unhooked the evap hose going to the carb Id bet the roll over valve has gas in it keeping the piston in the carb from lifting

Did you get to a solution on your ET4? Was it the CDI? Im also having same strange issue.

Recently got back a Ruckus and Metropolitan that I had loaned to my folks for the last several years. First they wouldn't start so I both cleaned the carb and replaced the idle jet (didn't want to go in twice after all and thats the most sensitive part). Started but would only idle. Any throttling bogged and killed the engine. Inadvertantly found that restricting airflow into the carb (pinched the hose with adjustable vise grips) increased idle. The vise grips worked to adjust idle by turning the screw on the pliers. So at high idle it would rev and operate normally - but it would have a significant pull at stop so that you had to either brake or plant your legs accordingly. Thought that was progress so went back in and cleaned the carb again, put it back together and same results. Went back in and cleaned again, this time buying the gallon sized industrial carb cleaner with the basket that you use to lower the carb into the gallon container. Same results. Took it to the local bike shop has an ultra sonic carb cleaner - presto! Now runs like it should.

it wound up being the CDI

-g