Modern Vespa

I ride my scoot every day and it's always been fine. Today I went off to play tennis but when I went to go home it proved a little reluctant to start - it idled badly and then quit - I set off home but it died on me every time I let it idle - finally it died on full throttle and refused to start again. The spark plug seems well attached, I filled it up with petrol a few days back, there were no warning lights, I did fall off my scoot 2 weeks ago but its been ridden every day without problems since.

Luckily I wasn't too many miles from home but sadly it was all uphill

Any ideas?

problems with fuel pump? random guess.

It's not the plug itself that is the problem, rather both ends of the HT cable. The cable has a thick insulator with three or four thick copper strands in there. The plug cap has a self-tapping type screw end which needs to be screwed into these copper wires. This is where the problem usually happens.

Also what is your code light doing?

You probably know all of this anyway Mike, just checking!

First, check the code LED gives the single flash and then stays off. Anything else and you'll have to read the manual for the codes and what they suggest.

If that's OK, while it won't start, check you have a spark at the plug. Assuming you have, it'll be a fuel issue. Blocked or loose fuel filter, duff fuel pump or power to it, or blocked injector. If you can hear the fuel pump prime when you turn the ignition on, the pump's OK and it's just a matter of finding why fuel isn't getting into the engine.

If there's no spark, it could be a bad connection of the HT lead into the plug connector, a duff coil, or the CDI has become faulty. The first two are easy to check, the latter can be checked by trying an unprogrammed unit - but you won't get one of those on a Sunday...

A couple of more things to check:

When you say "it was reluctant to start", do you mean that the starter did not turn over quickly and was slow to turn the engine?

Or did you mean that the starter turned normally but the engine would not ignite?

If you meant that the starter would not turn the engine quickly, you probably have a battery that is in desperate need of a charge or has gone bad. Even though it started, if the battery is low or going bad, the engine won't run well or at all.

If you meant that the starter turns normally, check the airbox to see if it's saturated with oil from when the scooter fell over.

+1

Thanks for all the responses guys - all very good ideas. I'd of replied immediately but I've been soaking in the bath after the push home. I think after you've pushed a bike for any distance then you get a new found respect for the engine and what it has to do!

The little red code light comes on briefly when all the other lights come on on the dashboard and then it stays off - I'm guessing that means it thinks things are fine.

The fuel pump makes it's normal noise when trying to start the engine so I think that's ok.

The starter does turn the engine as per normal but it just doesn't fire.

I'll have to check the air filter in the morning - actually I'll have to find out where it is first!

I thought it might be a vacuum in the tank but there was no sign of this when I opened the fuel tank.

I'll have to have a go at getting to the spark plug in the morning though it looks like it might be a bit of a game to get out.

There is room to get your hand in there as long as the engine is cold. Much more room than on the ET/LX. I'd feed the wire down to the bottom and remove the whole HT lead, which is easy to do. Agree with checking the plug and the air filter too though. Just in case.

It is easy to check the fuel injection system. If the injector isn't working you would get that little check engine led lighting up. Remove the fuel supply hose connetor from the injector unit and hold a cup under the hose. Turn the ignition on. The system will prime and you will get half a cup of fuel into the cup. Or so. Fuel supply checked...

a collapsed battery can give these symptoms and that includes showing light display.

I had a similar problem and it was the voltage regulator that went bad...the bike would start for about 10 seconds and only because it was running off the battery itself...not the bike...not saying that is what it is but I too pushed my bike home about 3 miles and at midnight....you do have a new found respect for the engine after that is correct.

The air filter was full of oil and crap - I've washed it and dried it now. I tried starting it without it on to see if that was the issue but it still won't start. Next bit is trying to get the spark plug off. 20 mins - you jest!! The battery is fine as it still turns the starter fine but I will but it on the charger anyway.

Wondered about shoving some "easy start" into the air filter. Also heard that redex (?) might help if squirted into the petrol tank. Anyway it;'s plug time now so that will keep me busy for the next couple of hours:)

Well - I can take the air filter off and put it on like a good un now!
I can also remove those side cowls quite quickly now to.
The fuses in the glove box are all fine to.

But I definitely can't get the spark plug off - I can get about 2 or 3 fingers on it and that's about it. It's making me wonder whether I have particularly large hands - you find yourself quietly looking at other peoples hands to see if they're noticeably smaller. My neighbour heard me swearing and came round to see what I was up to - he took one look at where the damn thing was and laughed. Suggestions?

Mike

Had the same symptoms this past Saturday. Was the battery. Replaced it and everything okay now.

Isn't there a tip-over sensor on our bikes that cause the fuel to shut off in case of a tip-over? I know most motorcycles have them. Perhaps this could be the problem. Maybe it has gone bad or stuck as a result of tipping over. It sounds as if everything else is OK, I'm doubting from what he is saying that there is anything wrong with the plug.

I'm thinking its ignition. The HT wire is notorious for coming loose, both at the plug end and at the coil end. The wire really isn't held in place very well, at either end - the spark plug boot and the coil output have these little sheet-metal-screw-looking affairs, that screw into the wire conductor from the butt-end of the wire. Seems the factory doesn't assemble them very solidly, and they're prone to coming apart.

Check for a solid connection at both ends of the wire. You may find it easier working from the underside of the bike, especially for working the coil end of the wire. Getting it up on a lift would be the thing for that.

I'm thinking the battery is ok since the starter cranks properly. There's no tip-over sensor on the GTS.

i have used pliers to gently grab the spark plug cap and wiggle it loose.

I'm still having issues removing the spark plug lead - I can get a couple of fingers round it but have very little leverage do do anything at that point. It does seem to be fixed quite solidly to the plug. I tried getting at it from the underside but my arms don't fit up any of the gaps - I did remove the lower cowling on that side to. I tried using pliers (normal and long nose) but the angle of the engine etc seems to stop any approach. There's also a thick tube (might be electrical, fluid or mechanical) running close by so I'm worried about just giving a berserker scream and pulling wildly at anything. Is there an image anywhere with someone just showing how to get to it? I also can't see where the wire goes to check the other end of the spark plug cable - it goes forward of the engine and seems to disappear. Maybe I'll look down at Halfords and treat myself to some bizarre spanner that might fit in the gap.

The battery is fine as the starter spins the engine but nothing starts or gets close to starting.

Perhaps I should get the grinder out and make myself a new hole

Maybe a really long pair of needlenose pliers??

Doug very kindly took pity on me and showed me how to get the damn thing off - turns out levering it with a longish spanner works well. He also managed to find the problem which was that the spark plug had built up so much deposits that there was no longer a gap - so no spark. We put in a new plug and up she fired !!!!

A big thank you to Doug for lending me your time and expertise.

Maybe I'll see if there's a Wiki article on removing the side cowls and air filter and if not I could do one - I know it's simple for most folks but I found it difficult.

Thanks for lunch, hospitality and banter Mike. Nice day for a little ride, despite it being diagonally across London from me. I'm doing a belt and roller change for Bill on the 14th I think, you may want to join us for that!

As for the spark plug, I have never seen anything like it. I did not expect to see anything wrong with it, as Mike's GTS has only 7000km. When I took it out the cause of the GTS's reluctance was very apparent. There was a track of metal or carbon from centre electrode to the outer one. No spark whatsover could have been produced. The Champion was duly replaced with an NGK and ran beautifully immeditely. Now get that oil changed!

For those of you who have difficulty getting the plug boot and cap of the plug itself, here's a little trick for you. A 19mm open-ended wrench (spanner) will slip over the end of the plug cap and catch under the little lip. This will give you enough leverage to get the plug cap off in the restricted compartment of the GTS. And perhaps the ET/LX as well...