Stig's 1'st Running Issue

[Stig / Major Tom]

Started yesterday at 25mph steady cruise engine is stumbling/hesitating. Accelerates and idles perfectly.
1)added more known good gas.
2)Checked oil (engine seizing?~~no)
3)Checked air filter and spark plug...they look good and clean.
4)Checked dragging brakes..again OK.
5)Checked for CELP codes...none.
6)Did throttle reset....on,off,etc. No improve ment.
7) checked for vacuum forming in gas tank. Not a problem.
8)disconnected battery to let ECU reset...no help.
9) Recent valve check...perfect.
10) Recent oils (engine & gears)
Today...might be even more pronounced stumbling at pretty much any slow or moderate STEADILY held speed....still idles fine, accelerates fine.

Issue came on slowly yesterday after one hour of riding at my normal speeds (25~38mph). Wouldn't bad gas have shown itself before an hour of riding?
Any ideas out there?
LIKE200iLX with @7000 miles, 16 mos old
Stig

[Stig / Major Tom]

Also, removed gas cap....came off with no sign of poor venting or vacuum forming.
Still some stumble after battery reconnected.......like a loose wire or someone is momentarily pinching off the gas line.
Thanks for any ideas.
(Got plenty of tools and some spare parts....but somebody on the crew needs to do a better job chekimg the stale date on these emergency tuna sandwiches.....fortunately the emergency Moon  Pies are good for 7 years,)

Stig.....sitting in the boonies pretty sure I'll make it home....

[Stig / Major Tom]

OK, decided there were two ways to remove suspect fuel:
1)with a line to a bucket
2)with a line to the engine

So, spent an hour giving my scoot an Italian Tune Up to get rid of the 1/2tank of gas. (laced with Sea Foam)
Found some great new roads, and had my first real experiences with WOT & near-WOT. My tach showed 8500 RPM's when I finished, and I saw 61MPH as I blasted 4 times up and down a local limited access 55mph highway.
Came home on fumes.
I noted that the scooter ran p e r f e c t l y at these high speeds. Never detected a bit of hesitation or stumble - but maybe was just blasting thru it at those speeds?
Will refuel with different fuel can and see if the Steady 30mph Stumble is still there. (it is not always a minor stumble - sometimes feels like the engine is going to quit) Failing other alternatives - if it's still broke - will call the shop since the engine is still under warranty.
Stig

[tortoise]

[TroutBum]

Stig, when that happened to me and the starter working sporadicly it turned out to be the ground engine block ground cable. As you may recall the bolt holding the cable near the starter motor came loose and the cable was just resting on the engine. It ran fine, but would cutout and spudder at speeds you indicated. Check to see if your ground wire has come loose. Also, check the connections on your battery while your at it. You may also want to add 2 ounces of SeaFoam or some Techron with the next few fill ups to aid in the injector cleaning.

[TroutBum]

Stig,

Check the puke tube as well. If it's filled just remove the plug and place a cup under it while running the engine on idle for a few minutes.

[Stig / Major Tom]

It's

Stig,

Check the puke tube as well. If it's filled just remove the plug and place a cup under it while running the engine on idle for a few minutes.

Troutbum,
Thanks for the 2 suggestions.
I checked both,  and battery connections, no.issue.
s found.

Still trying to sort it
Stig

[big blue]

Stig- Just a thought. I had a similar problem with my 97 VW Golf. Turned out to be the clip holding the fuel injector was misaligned after a spark plug change. I pushed in the injector and clicked in the spring holder and the problem was solved. I would also check the intake manifold for leakage due to a crack or a clamp that may have loosened.

[DMblues01]

Hey Stig!
I have a dumb suggestion, (because that's my personal specialty!).
How long since the fuel filter has been changed?
If it's been a while, you might try that since it's a fairly cheap thing to swap out.
Just an idea. I've never claimed to be a BIG help! 

[Stig / Major Tom]

Hey Stig!
I have a dumb suggestion, (because that's my personal specialty!).
How long since the fuel filter has been changed?
If it's been a while, you might try that since it's a fairly cheap thing to swap out.
Just an idea. I've never claimed to be a BIG help! 

DMbloos,
Thanks for the idea...if this thing has a fuel filter it must be in the tank, on the fuel pump assy in there, beyond my reach. I'm going to kick around some more ideas - maybe even call the dealer since it is still under warranty for 10 more mos., if the Sea Foam doesn't do the trick in 2 or 3 tanks.
Stig

[Stig / Major Tom]

On 3rd tank with sea foam....no improvement, after 20mins seems less bad. Maybe. Still.no celp fault codes.
Stig

[DMblues01]

DMbloos,
Thanks for the idea...if this thing has a fuel filter it must be in the tank, on the fuel pump assy in there, beyond my reach. I'm going to kick around some more ideas - maybe even call the dealer since it is still under warranty for 10 more mos., if the Sea Foam doesn't do the trick in 2 or 3 tanks.
Stig

I would have thought that it would still have a fuel filter somewhere in the fuel line. Even all my fuel injected cars I've owned had an inline fuel filter to keep crud from the tank from cocking up the fuel injection.

[TroutBum]

Stig,

Did you over fill the tank at all? I'm wondering if the evap canister is filled with fuel. This can cause sporadic performance.

[Stig / Major Tom]

Stig,

Did you over fill the tank at all? I'm wondering if the evap canister is filled with fuel. This can cause sporadic performance.

Have no idea....think not. Did change out valve snd lines from the  fuel neck vent.
SYM folks rip out the whole evap/tree~hugger  system....I'd like to do that.
Checked more grounds today, retightened intake breather fittings, checked.exhaust bolts, replaced reg NGK with iridium because of its ability to fire under less than ideal conditions.
Refitted and tightened injector, and plug wire to coil.
Beginning to think something quit working rather than something came loose.
Injector, ECU, coil, ....? Still no celp fault codes.
Will try calling the Vespa/Aprilia dealer for service.
Stig

[200i]

Stig,
Sorry for your troubles...I'd change the plug just to be doing if I had an extra.