Modern Vespa

Hi
Trying to get rid of a flat spot for ages. I have recently removed the engine and:

- new spark plug (Champion RG4 HC just in case)
- Checked valves clearances (only slightly out)
-blanked off the SAS Secondary Air gizmo and also blanked off the stem of a t-connector (on the vacuum line between the inlet manifold and the fuel area)

Scoot now starts beautifully, has a better tick over - nice and steady - and the scooter is now much much better on steadily applied acceleration.

But.... it still has a tendency to stall / falter on cracking open the throttle too suddenly when stationary. (Tommy Cooper would say "well, don't do it then"!!) and there is a lag of about 1/2 second when doing the same when on the move. Steady, gentle throttle action is necessary.

I have settled on 4 turns (4X180 degrees) out on the mixture brass screw on the carb because the faltering is worse either side of that - I've tried 5 and 6 turns and 2 and 3 turns (oddly its faltering /dying behaviour seems equally badly either side of 4 turns)

Is there anything else that I should be checking or adjusting?Many thanks

Hugh
Have you tried replacing the Ignition coil an/or the HT lead? Worth a try...
Hugh

Hi Hugh
Thanks
I'll try that
Hugh

Hi Hugh
Wow! It worked. I got a "performance coil 30k volts etc - not expecting it to make a difference but it did! It transformed the scoot - running perfectly for the first time in 3 years! Pulls away perfectly every time - starts immediately etc....
Thanks Hugh
Hugh

I will try that too. Every quick twist of the throttle at just about any speed gives me the half-second hiccup. Seemed worse after adding Malossi 187 cylinder kit. Which one did you get?

Greetings:

Quoth Cubella: I had a similar throttle-balky behavior. First, consider a 38 pilot if not already installed. I had to resort to a similar 4+ turns out on the idle mixture screw, and that's a big clue that your pilot is too small, OR...

Second, if you still have the charcoal canister setup, consider deleting, or at least dismount and check all the hoses for cracking - vacuum leak makes it impossible to tune. My 187 became SO much more civilized with these changes.

Mine was worse than that. Had to be nursed away from a stop and would die if too much throttle was applied. I'm in the UK, but FWIW, here is what I bought:

https://www.ebay.co.uk/itm/Vespa-GT-125-L-Granturismo-2004-Ignition-Coil-High-Power-JMP/184037452896?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I think it was not the high-performance bit that made the difference - I think it was simply a faulty old unit (or HT lead or HT cap). I hope that helps.

[quote="Wheelman-111"]Greetings:

Quoth Cubella: Is a turn 180 degrees or 360 degrees?

Greetings:

I call a full 360 degree spin a "turn". Generally 1-3 means the pilot is close.

Wheelman, I yanked the canister long ago, agree it transformed the engine, especially starting. Now if I can just get rid of this little burp on quick throttle twists...

Greetings:

Yes it was hard to believe just reading descriptions of others' experience removing the Evap setup until I did it myself. I guess it's hard to describe "balky" carb behavior in words on a screen.

Your issue just doesn't sound like an Electrical problem to me. The "Handoff" from low speed to midrange depends on a sufficiently large Pilot, mostly. Slide cutout and main jet needle secondarily assist a Seamless transition. Could it be that your pilot is starting to become obstructed with Resin? Or do you still have the original 34?

I tried to document my experience with my own 187 kit installation and the carb changes I needed to perform afterward in my ISO thread and elsewhere, but see the second sentence of this post above.

Agreed, I don't think it's electrical. The scoot is a 2004 ET4 that was in the family since new and I acquired it a year ago July with only 800 miles post-carb cleaning and new fluids. It still has the stock jet as advised by the tuner who did my 187. I did the Malossi variator myself. A different jet would be a cheap try-out for sure

Greetings:

Quoth Cubella: Um, FREE actually. If you want, PM me an address and I'll send you this one for Walbro. I actually have the Long version for Keihin as well. I don't know how jets in my kit accumulate, but for some reason I have spares of sizes I usually don't need... Maybe they multiply?

Well that would be awesome and I will take you up on that...as soon as I find out what caused our 3800 miles of carefree riding to end today. Cruising along with wife aboard, 35 mph, a sudden thump noise, engine quits and we coast to a stop. Uber then rented a pickup to get it home. Hoping beyond hope that the belt gave way and wrapped itself around the variator but don't know yet

Greetings:

Sucks!! Hope it's a belt too, perhaps a bit over service life? Lemme know when/if you'd like the jet.

Thanks, I will let you know, and thanks again for the kind offer. Belt is intact, engine appears to be seized. Or at least the starter can't turn it over, and well, that ain't good...

Greetings:

Being the veteran of a number of engine seizures, I'd expect at least a brief lock-up of the rear wheel. Glad you and passenger stayed upright.

Very good point. There was no wheel lockup, not even a jerk. Just a quiet coast to a stop for me and the missus. But something's gotta busted up in there with the crankshaft having about a half inch of travel and clanging up against something internally.