Modern Vespa

Hi there..

I found it yesterday a bit strange a problem with my GTS Supper 300 HPE.. I was riding up in the mountain and on my way down I killed the engine off with the red button, but not the ignition..

I set back the red button to the start position and When I tried to restart the engine it didnt turn on.. I have only 800 km in this bike, and is absolutely new..

Sometime just made the noise of trying to turn on but no succes.. after several attepmts it did turn on... I tried another time and the same thing happend..
When I arrived home i turn off the engine and made several attempts all of them succesfull...

Is there any explenation from you guys ???

The lesson is to never use the kill switch (red switch) unless in an emergency.

I know that if a carburetted scooter had the kill switch turned off while coasting downhill, the engine would flood as the clutch would not disengage until the speed slowed right down. However, with a fuel injected engine the fuel supply is absolutely cut off when the kill switch is turned off.

You have activated self-destruction but fortunately you have acted in time.
Probably the red button also interrupts the fuel pump that has been momentarily emptied.

Hi Armandqipo,

So, if you used the 'kill switch' when the bike was going downhill and the clutch was engaged with the engine, this will probably have caused the spark plug to become partially fouled with oil. If your bike has only 800km's on the clock the engine will have sucked oil into the combustion chamber, especially if the downhill decent was a long one (how far down the hill was it?). The piston and rings are not yet seated to the cylinder so there is always some oil that will be sucked up. This happens even with a fully run in engine too but to a lesser extent. So never do that, as jim says, the kill switch is only to be used in an emergency or for the occasional turning off of the engine to make sure the switch stays in working condition.

There is no need to turn off the engine with the kill switch while riding/moving at any time and it could be dangerous to do so. Incidentally, as jim says, when riding your scooter with the throttle closed, such as going downhill, no petrol enters the combustion chamber so you are not wasting fuel.

To cure you bikes problem the spark plug should be removed and inspected. It may be possible to clean it but replacing it may be best as you cannot get all the debris out from around the insulator. I would let the dealer do this. Tell him what has happened. Of course, there could be something else that has caused this but without a detailed inspection it's hard to know. My bet is that it's the spark plug.

Thank you guys for the information.. It was really helpful for me..

No i understand what might have happened

Double check the spark plug wire is pushed all the way on so it snaps in the lock position. My HPE came from the factory with a not-quite-tight plug wire, worked fine for 37 miles then fell off. Yours might just be loose and making connection sometimes.

Checking will take 30 seconds. Pull out pet carrier and push plug wire on. Takes some force.

To the other commenters: what's the difference between coasting with the throttle closed and coasting with the kill switch off? No gas enters chamber in either event and oil would be sucked past rings in either event if in fact that happens. I wouldn't think the plug sparking with no fuel would burn an tiny bit of oil that might be present.

PS:. Motorcycle safety courses teach riders to always use the kill switch to turn off motor so they have the muscle memory to do it in an emergency. I confess I usually use my kickstand to turn off the motor when parking.

Wolfeboats, checking the spark plug lead a good idea.

Difference between decending a hill with the throttle closed but engine switched on, and decending a hill with the kill switch off is that the spark plug will not keep itself clean with the kill switch in the 'off' position. With the spark plug 'igniting' with each rotation of the crank at least twice (you get a dead spark too), it does keep the electrodes clear. It is usually only small amounts of oil that will contaminate the electrodes on the plug, but this can build up if the period of travel downhill is prolonged with a dead engine. With the engine on but closed throttle the plug is sparking at very high voltage at around 25,000-30,000 volts, more than enough to keep the electrodes clean.

It's fine to kill the engine with the kill switch if you are stationary/parking but not best regular practice as you may forget to turn off the ignition. Same with side stand, it's ok but remember to switch off the ignition.

Also, the throttle being closed does allow a small amount of fuel in, enough for the bike to idle. Only in the US for some unfathomable reason - in the UK instructors emphasise it's for emergency use only. It's all to easy to forget to turn the key off or to remove the key if you use the kill switch to turn off on a regular basis. There have been loads of posts on MV of people forgetting to turn off the ignition with drained batteries, burnt headlight lenses having hung their jacket over the front and even stolen bikes on occasion.

The muscle memory theory makes no sense - the emergency is almost always when a bike's gone down with the engine still running. No hands on the bars in this instance - but the red kill switch should be reachable by any passer-by even when the ignition key location or operation isn't known.

Hirers of scooters in Europe often (naughtily) bypass the kill-switch, as without this they get far too many cries for help when the bike won't start.

I use the kill switch all the time to stop all my bikes and have never had a problem. Muscle memory is a powerful thing and I do believe it helps. Maybe back in the day it wasn't a great idea but I see no problem with modern bikes.

As a bonus when some yahoo plays the old flick the kill switch joke you'll be just fine and not sitting on the bike trying to figure out why it won't start

Instructors here DO teach riders to use it.

Jim, many bikes don't allow any fuel into the combustion chamber on closed throttle until near idle speed is reached. The ecu take complete control of the fuelling process these days jonly injecting when just above idle is reached. It reduces emmisson and enables bikes to meet euro 4.

Not all Harbinger. I'm a bike instructor (part time) of 12 years experience and when visiting the States made it my business to connect with fellow colleague instructors. Some do, but it's a contentious issue for some reason. It's ok to use it when stationary of course, but you run the risk of forgetting to turn off the ignition as jim says.

I can add that not all scooters have the emergency switch on the handlebar. The hazzard would be more useful and some have it...(mine is both missing).

Ah, thanks.

Piaggio/Vespa kill switch aren't the best, one on my MP3 is acting flakey now. And it needs to be changed.

What muscle memory can be brought into play when the bike's on its side down the road? Your hands won't be on the handlebars at that stage...

I know muscle memory is very useful, but please describe an emergency that occurs to bikes while you're riding it that would make you instinctively hit the kill switch...

Simple - You know where it is. That may not be "muscle memory" BUT at least you will be FAR more aware of it's existence. I don't understand your opinion against using it on a modern fuel injected bike. You certainly disagree with the trained professional instructors over here.

If it were like on cars, there should be an inertial switch but connected to the inclination of the vehicle so that by detecting the horizontal position it automatically turns it off; the emergency switch is used for this, to turn off the scooter when you have an accident and you fall.

I guess the USA and the rest of the world will have to agree to disagree.

The only thing I might add is that kill switch failures seem quite rare - except in the US.

So Armandqipo, what was the reason for the hard starting?

Already especially with the English language.

But more with measurement systems, it's all with the metric system

I checked the plugs all seem to be ok.. I dont know if any is losing something but the sooter is running fine now and i havent touch anything since then..

for sure i havent test it again with the killing switch on downhill again..

I've read posts recommending the use of the kill switch with immediate key turn off afterwards. So I am aware and will use the kill in whatever emergency I need to as well as beginning the turn off sequence.
Last week I dropped the scoot from a running standstill. Looked behind me and the GTS tilted to the point that I wasn't strong enough to recover. We fell gently but it cost me a new brake lever. I was prepared to hit the kill but the motor stopped on its own. Is there a internal thing which will shut off the engine automatically? We fell to the left.

Yes, there is an automatic 'kill switch' under the floor. It's called the 'tip over switch'.

Armandqipo, what has most likely happened is that the spark plug has now burned itself clean. If you don't have any further issues then that was the cause for sure.