Modern Vespa

My 400 has been running great with 13K+ miles. However, something occurred this morning that has never happened ....

I came to a stop and enabled the tilt lock. A few seconds thereafter, with my rear brake engaged, the idle surged up just enough to disengage the tilt lock. Fortunately, my feet prevented the scooter from dropping and my brake prevented the scooter from moving forward.

I didn't throttle and I was firmly planted on the seat (the seat sensor didn't display). Any ideas as to why the scooter would surge? It's never done it before.

I rode another 30 miles and stopped several times without a hitch. I am just worried about this happening when I warm up the scooter.

Eric

as long as your not sitting on the seat it can't go anywhere.

when was the last time you cleaned the throttle body?

You're right! It can't go anywhere unless I am sitting on it.

About 1500 miles ago, I sprayed the throttle body at least 7 times while running at 3K rpm.

did you pull the airbag tube and spray directly into the throttle body? or just thru the air box?

I sprayed directly into the small hole above the flap.

This happens on mine. The tickover can't spike when I'm not on the bike (but it will sometimes cut out because it's trying to over rev). But the tilt lock will often disengage when I am sat on the bike due to a spike in the tickover. Isn't it a sign of a faulty voltage regulator?

Probably worth ruling out anything mechanical first. Is there enough play in the throttle cables? Is there any tendency for the revs to increase when you turn the steering to full lock? Any chance that the throttle cable has started to fray and stick, has the twistgrip action got stiffer? With the engine off can you hear a nice sharp tap when you close the throttle and it hits the stop on the throttle housing?

If that's all OK then either the idle air control valve is misbehaving electronically or you have an air leak downstream from the butterfly.

I had this happen to me once, and I never use the tilt lock at an intersection anymore for short stops. On my MP3/250, I would have caught it like you did, but on my MP3/500, I probably would have went over. I Only use when stopping and parking. When parking in the Garage, I put on the Center Stand, hit Reset and take the pressure off the seals.

Keith,
Marietta, GA

There's enough play on my throttle and I can hear the tap when I close it while the scooter is off. Idle is normal when at the full lock position.

I've ridden 200+ miles since the incident without experiencing another issue. How often should I spray the throttle body? It's been about 1700 miles since I sprayed into it.

Eric

you should be good on the throttle body cleaning. I do mine before every plug change, then install the new plugs afterward.