Modern Vespa

Since forever my 500 would at times hesitate at around 4-5000 rpm. but a quick goosing of the throttle would 'seem to clear things' and I would carry on.

This time at the end of a 1000 mile road trip I was (first time ever) running with the traffic at between 70-80 mph when it happened again. However I had no more throttle to give and it lost all power, then had to quickly cross 2 lanes on the Interstate to get out of Friday the 13th traffic. Very scary !!!

The engine was still running at normal idle when I stopped, and once my heart rate did likewise I was able to continue, although at a more conservative rate of knots. I did notice a wee bit of the usual hesitation a few times at lower rpm, but got home safely.

So, what's up ??

Thanks for your help.

I have had a similar issue where my MP3 500 has hesitated at high speed and then died when I have pulled over. I have put this down to an electrical as a flick off and on with the killswitch and the bike has restarted and continued without issue.

We do get a lot of rain in ghe UK and my scoot is stored outside so damp can be a problem.

lots of things to check

spark plugs
spark plug wires
air filter
kill switch corrosion
throttle body cleanliness
fuel injector for cracking and cleanliness
throttle cables on throttle body smooth operation not hanging up/binding

Thanks OAD. I had done the plugs, throttle body and air filter just before heading out. I'll do the kill switch next and check the cables. Now to get to the fuel injector is the problem. What tupperware needs removing, and would any cracking be visible to the naked eye?

Thanks for your help

I mentioned the kill switch in another post because I had a similar problem. I used WD40 and had no issues since. I've driven in heavy rain since then too.

Did the kill switch last night, quite easy when I found a very small nozzle to fit onto the end of the tube of grease.

Now for the hard bit........Which panels come off to gain access to the fuel injector ?

Thanks

you should be able to to it thru the access panel in the pet carrier right behind the battery.

Thanks OAD got the injector off and onto the bench.

I watched a real neat U'tube video on cleaning out injectors by using carb cleaner and hooking the 2 electrical connections up to a 12 volt battery.
I've tried to duplicate (see photo)

Is 12 volt the proper voltage to use, and does it matter which way I hook up my alligator clips ??

Many thanks

you should be able to go back to the connector on the scooter and check continuity to ground then the other pin would be your positive 12 v and just power the injector the same from the 12 v source

Don't forget fuel tank venting.

tom

Ha! .......so obvious, now you mention it. Thanks


Sanquhar says:

Don't forget fuel tank venting.

tom

In what way?

I think Sanqhar was saying that restricted venting might be the cause of your hesitation problem. Have you ever heard a whoosh when removing your gas cap?

No whoosh experience, but I do have the open loop set up when I removed the rollover valve. I'll do a double check anyway. Thanks

High speed miss:

Replaced the kill switch......still had problem.
New spark plug & wire....problem still there.
(EVAP was removed early on, tank vented)
Computer said oxygen sensor & FI were bad......
......replaced, problem solved.

Was this the dealers computer, or did you have some other means of testing?

Great information.

Thanks for sharing.

Dealers computer.......Vespa Seattle aka Big Peoples Scooters. Have done business with them for years. Victor and his crew are first rate!

Might be a little tough riding to Seattle this time of year ........

You're lucky to have found a reliable/knowledgeable dealer.

........and thanks for the info. I'll look around locally and see what's available.

Thanks again.