Modern Vespa

Hello everyone!

I recently changed out the wheels to my Vespa, a 2019 gts 300 super, and added the tone wheel kit on the back wheel that allows you to attach it to third party wheels. But upon starting it and rolling out, I've noticed it won't let me accelerate past a certain speed (around 20-30 mph). I've also noticed during this time, the front brake feels like it doesn't want to work as well. After riding it a lil bit, what will happen is the ABS and check engine light will come on and suddenly it accelerates as it should and the front brake is working again. Any suggestions on where to begin troubleshooting would be greatly appreciated. Speedo works as it should though which adds to my confusion. The code coming up is P2158 "Vehicle Speed Sensor B".

ABS light means wheel sensor issue.

Common causes of issue after a change: bent or gap. gap should be approx 1-1.5mm all the way around.

Check both front+rear but I think it's your front.

I'll be checking in the am! Thanks for the suggestions!

Turns out, I'm more used to my bicycle and brakes are reversed. It's my rear brakes that are being wonky, the left handle. Once I get a chance to get it up on a lift I'm gonna take a look at spacing for the sensor from the tone wheel. Fingers crossed that's the issue. Although I don't understand why the speedometer would work but ABS would not.

Recently did the same on mine. Had to add a washer under the sensor for spacing. Check there first.

abs and asr both require both sensors working. speedo only requires one (the rear one).


also can check the sensors without a bike left or stand or jack or anything.

You're absolutely right steelbyte, I definitely can. But I'm a biiig boy and it's hard to get in there from the ground. lol

That being said, I'm gonna just suck it up and look around again tonight to get some measurements for them from the tonewheel. Hoping the washer stuff is the issue.