Modern Vespa

I searched past threads to see what exactly the seat sensor does. I didn't even know I had one until I removed the seat to install Utopia drivers backrest. unless I am missing it, I am not seeing anything in my 400 owners manual and the old threads list a number of problems people have had but don't tell me exactly what it does in laymens terms. I don't want to modify or bypass mine, just want to know the purpose. Thanks

The sensor lets the computer know that the operator is seated. If you take your weight off the seat, the computer will limit engine rpm until you get back on.

(Yes, there is a manual override; let's not have that argument again.)

Try this:

Sit on the seat with suspension locked, take off like normal, seat sensor senses you and unlocks the suspension and you go.

Now, stop and lock the suspension again, but this time stand up off the seat and give it throttle, the RPM will be held below 2,000 RPM, the suspension will not unlock and you won't move.

Now lock the suspension again and then take your weight off the seat with your feet on the ground, now tap the tilt lock switch in the unlock position 2 times very fast and it will unlock. This is a by pass whether you are on the seat or not.

Hope that explains the tilt lock and seat sensor relation.

ty stooterboy. excellent explaination. ty so much

Glad I made it clearer how it works.

If the engine is running and you get off the seat a red light appears and supposedly it limits the RPM to 2,000. I can understand this sometimes but what if I am riding on grass or uneven ground, will it drop the RPM? I was taught by the MSF that when you go over railroad tracks to stand up,otherwise you will bounce all over and the throttle will inadvertently throw you off the bike or make it herky jerky. Why would I want that?

Go ahead and try it when you are in a parking lot with no one around.. You'll be shocked about what happens..

If you're moving at 'riding' speed with the tilt lock off, your engine will not be rev limited. The seat sensor interlock is there to prevent unlocking the tilt lock when stopped and no rider is seated. I frequently take my butt off the seat when crossing rough areas like tracks or pocked roads and engine speed stays constant. If you're attempting to cross tracks or uneven surfaces with tilt on, you're surely going down.

The seat sensor only comes into play after you've initiated the tilt lock in my understanding and experience. It won't lock out the suspension while riding; it's only there to keep you from dropping the bike while parked or from a stand still.

Not quite correct - it will always limit revs whether the tilt lock is engaged or not when RPM is at idle and the bike isn't not moving. If you have tilt lock on it will not release the tilt lock unless you are sitting on the seat. It also will "stutter" the engine as an indication you are being limited - the limiting itself does not create the stutter. Once you are actually moving it will not prevent anything.
Basically it's to *help* prevent you from dropping the bike and/or having it zip off through your yard without you. This for the myriad of folks that have never ridden a CVT equipped machine and are expecting the bike to be "out of gear".

your not quite right here Bubba. try putting the scoot on center stand , double click the tilt lock off and see if you can rev the engine. Yes you can. The seat sensor ONLY limits when the tilt lock is on.

Hmmmm - I'll have to double check that - I would have swore that the last time I did that it would not let me rev even with the front unlocked unless I put a weight (cinderblock) on the seat.

I think in most all cases I like the idea and as long as it doesn't take over while I am moving, it is ok with me. For a while there, I thought I would have to walk the scoot over the railroad tracks.

Yeah no worries. Has no effect at all unless your front is locked.

OAD is correct as usual. When I first got my MP3 I was worried about this because if like Bubba suggested the rev limited activates whether or not the tilt lock is on it could create a dangerous situation in case of a failure (the tilt lock, for example, has a failure mode of dropping when stopped, an inconvenience; as opposed to locking while moving, potentially fatal). So when you think about it, the sensor would have to be tied to lock as any other situation could be highly dangerous in a single- or double-failure condition. I put the bike up on the stand to check this out and found that the seat sensor deactivated once the lock was off; I was able to rev the wheel on the center stand with tilt-lock off.

Will an Airhawk fitted to the seat of a Fuoco 500 interfere with the operation of the seat sensor on any way.

No. At least it has never interfered with mine.

Thank you - does it improve the geometry of the seat in the sense of the feeling of sliding toward the front

some, but a help fix is to install some extra washers as spacers in the front seat mount plate to raise the front up a bit. you will need to get some longer bolts. I would not go over 3/4" in extra spacers.

Tried it - wasn't happy with the result - see my post on "Seat comfort required"

I raise my rear all the time with no problems.
It only engages at 2000rpm or lower.