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GT200 & GTS250 & NC750X & Royal Enfield Pegasus
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I was having issues with my scooter stalling when taking off after a cold start. It would start no problem and, after 1 min riding, it would run perfectly as well. The problem was when I initially turned the throttle to set off it would just immediately cut out. I decided it probably needed a new spark plug so I bought a CR8EKB spark plug and installed it (what a pain!).

Now I can't get the bike to fire at all and I'm not sure what I've done wrong. I do have a new air filter on order but I don't think that would be an issue. The lead appears to be on fine and the spark plug feels pretty firmly in place.

Any ideas?
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'05 NINJA 250 (in sick bay), '09 TMAX, '13 GTS300, '13 CITYCOM, '14 NINJA 650 ABS
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well if it fired before (albeit it with issues), i would suggest pulling the plug and checking the gap. then make sure you've seated and screwed it in correctly and then snugly fitted the spark plug cap.
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Thanks for replying.

I pulled the plug and held it against the engine while pressing the starter. The spark looked good. I assume the gap is ok because the plug is new (I bought a new one yesterday). I also tried using both brake levers and tried turning the on/off run switch back and forth a dozen times just in case.

I put it back in the engine and this time tried twisting the throttle back and forth (I don't normally have to do this) and eventually it started. After 10 seconds it would idle ok without me playing with the throttle. Could it be the air filter? I have another one on order and hope to pick it up today if I can get there. The fuel level is also low and on the last bar - could this be an issue? The problem started about a week ago so possibly bad fuel? I heard people mention bad fuel on the forum but I've never experienced this or know of anyone else who has (outside of travelling in Africa etc). I'll fill up anyway.

Any other ideas?
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vespa gts 300i super
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Yes it could be air filterif its clogged up badly,
,try cleaning ,won't no harm ,its also possible that carb has a blocked jet ,try the simple things first,before taking carb off
check carb manifold for leaks
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Just remove the filter element & try starting it. If it starts you know what the problem is.
There's a small air passage in the injector that controls the idle. Could be that it's clogged (not uncommon).
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I have a new air filter on order. It was supposed to arrive yesterday but might now be tomorrow. It's still wearing the one in came with in 2008 so I'm guessing it's probably time for a new one.

That's a good idea regards running without the filter just to see if that's the issue but it's such a game taking the things on and off I might just install the new filter anyway. The GTS 250 has injectors so would it be worth squirting some injector cleaner into the fuel? How do I check for leaks? am I looking for fuel leaking or broken/cracked pipes?

It only seems to exhibit the problem when the engine is cold ie first thing in the morning. Not sure if this is a pointer or not.
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Here's the service manual take on it:
Quote:
Engine stops at idle
ENGINE DOES NOT HOLD IDLING/ IDLING IS UNSTABLE/ IDLING TOO LOW
Possible Cause: Operation


Presence of faults detected by the self diagnosis:
Pump relay, HV coil, Injector, revolution timing sensor, Air temperature, Coolant temperature.

Ignition efficiency:
Spark plug, Ignition timing

Correctness of the parameters:
Throttle valve position sensor, Stepper, Coolant temperature sensor, Intake air temperature sensor

Intake system cleaning:
Air filter, Diffuser and gas sensor Supplementary air pipe Stepper

Intake system seal (infiltrations)
Intake manifold - head, throttle body - manifold
And here's some info on the idle bypass:

Here's a page with more info on the idle air bypass (aka Stepper or Supplementary air pipe Stepper):

http://cheekythoma3.wix.com/itsme#!idle/cy6q
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To be honest I don't know what half (any?) of those things are. I'll try the new air filter and the injector clean additive and I'll also feel around for any obvious breaks/cracks around the carb.
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Well, do what you can and see if it helps. The service manual has descriptions of most of tasks (supplemented with various service procedures on youtube etc.) Have you kept up with the recommended service intervals? Again they're in the manual. If you have, Vespas are pretty reliable. If you haven't you can run into mechanical problems much sooner than you would with a car (smaller engine, less fluids, shorter service intervals). Honestly, guesses will probably cost more money than having it sorted right the first time. (I'm still using the original air filter in my 2007 GTS- they're washable & reusable.)
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it is likely gapped correctly, and if you have an auto parts store nearby, a spark plug gap tool should cost that much. Millimeters count.

I was having a hard start issue (also had to kinda gun the throttle) and also had a dying out when I was coasting to idle at stoplights.

I pulled the plug and found one of the 2 prongs was wider than spec. So maybe it didn't arc all the way? At any rate, I cleaned it with a brash brush and some brake cleaner, and then re-gapped it to spec and put everything back snugly.

It started up easily just like when I got it and didn't have any die outs when I was riding it around this past Monday.

I use seafoam for engine cleaning.
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I'm pretty sure it was gapped fine. I changed the plug and the air filter and it seems to be running fine now. My suspicion was it was just the lead getting a little corroded or perhaps the lead just needed to fit better on the plug. Interestingly the old air filter after 7 years on the bike still looked quite clean.

Why does the air filter box need 6 screws to hold it on? why is each screw recessed down a dark hole and why do you need to then get the screw head into a small hole? it looks like something that could be done with a simple tab on one side and a clip on the other. I suppose it is nice to know that if the scooter does explode then at least my air filter will be held in place.
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All the screws are there to keep the filter edges air-tight (clamped between plastic ridges) so that the air getting into the engine is all filtered.
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Check the fuel injector itself...They do go bad...Ask me how I know...
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