Modern Vespa

I dunno what happend.. Was riding just fine when all of a sudden the bike shut down.

Pulled over, figured maybe I needed to switch to reserve. Switched over and gave it a few kicks... nothing.

Let it sit a few minutes, kicked it again, started idling REAL weakly. Gave it a little gas and it sputtered and died again.

Tinkered for a bit:

Spark: good
Plug: clean
Carb: intact and adjusted
Wires: a mess but they were always kinda a mess, everything was where it was the last time i checked though. to the best of my knowledge.

No clue what the problem is, when i twist the throttle more than a few degrees the motor bogs and goes down to like litterally maybe 100rpm "putt......puttt..........putt..."

I could get it into gear and was like 5 miles from my house so I ducked off the main road into a nehborhood and rode the bike lanes all the way home at about 10mph (any faster and the bike would die)

I'm not sure what to start with, any ideas?

More then 10mph and you flood the engine? Or can't change out of gear? Sounds like a cable issue but I would pm Greasy.

Idle jet clogged?

How clean is your fuel tank?

Did you try running it with the choke on, and did it change things?



I mean ... when there's an issue, you just gotta remember that the bike needs three things to run : Spark, Fuel and Compression. Checking for spark means everything from the plug back to the coil and back to the stator ...cap, wire, ht coil, etc.
Checking for fuel means not only is GAS getting into the carb and into the engine, but AIR as well ... is your air filter clogged or saturated with burped up gas? That can choke out your engine ...it's happened to me. Sometimes i'll run the carb without the air filter on it when troubleshooting to ensure proper air flow.

Compression is something that if you HAD, you almost certainly still HAVE unless something catastrophically failed... i usually only go testing for compression on bikes that i've not looked at a while, to see if seals / piston rings / etc need replaced.

nocattle:

the bike would shift just fine, so luckly i could jsut shift to keep the bike in low rpm.

eric:

The fuel looks pretty clean, when I open the tank i can see right to the bottom, there's actually no noticable particles floating around, the gas looks clear as can be (with a tint from the oil of course.)

The carb's compartment is very "wet." I hadn't thought to check for a fouled air filter, I'll do that later today.

My bike actually runs like crap with the air filter off and wont' tollerate higher rpm, though it's nothing like what's happening now.

It does sound like maybe the bike isn't getting enough air, so I'll start there and see what happens, thanks for the tip.

I assume we're talking about a vintage scoot. It might help to know if it's electronic ignition or not. I had my coil on my SS180 go bad. It would run great when cold and then suddenly cut off just like you'd hit the kill switch. Sometimes it would restart right away but usually not.

I also rewired the stator shortly after I got it. The wires had rotten insulation coming off of the stator. Good luck. I hope you get it sorted.

Well I found the problem. Since my computer decided it no longer wanted to work (long, angry story) I had all day off and to myself, decided to systematically take my Vespa apart.

So I ran the bike with the tank on "off" till it ran out of gas.

Removed the tank.

Removed the carb.

Dismantled the carb.

BINGO.


I don't know the part name, but the cap to the injection nossle had fallen off... So when the throttle was closed the bike would more or less idle ok, but when I opened the throttle, instead of a pinprick for the gas to flow through, it had a hole about half the diameter of a no.2 pencil.

FLOOD FLOOD FLOOD.

Thanks to Eric, who suggested running the bike w/o the air filter, I discovered the bike was running just fine w/o the air filter. That's odd because USUALLY my bike runs terrible with it off. Too much air, too much gas.

I sprayed off all the itty bitty bits of the carb with some spray cleaner.

Let everything dry off.

Cleaned out the filthy compartment the carb sits in.

Re-assembled everything and...

Runnin' just fine.






I'm currently typing this on my freshly formated computer. /sigh/ nothing's easy these days.

Anyway I thought I'd type all that up incase anyone ends up in my thread with the same problem. On the plus side, I learned that by takeing out the gas tank, small frames are DAMN easy to work on. Yay.

You da' man, boss! Way to go on the troubleshooting...

yeah, with all the computer work I've done in the last few years, I sort of forgot how rewarding it is to work on machinery with my hands.

I just wish I hadn't had to push it home in the cross walks with full lights of cars on Lawrence Expressway gawking at me.

All's good now. When we gonna go for that ride?

Well, VCLG's 1st Sunday o' the Month ride is this weekend, and I'm planning on doing that one. I have plans for Saturday late-afternoon and night, but I could do something in the morning.

GREAT JOB!!!! i could only suggest a clogged jet because that happened to me..booo!!!

come on out sunday!!! maybe us santa clara kids can ride over to LG together

can you fix my smallframe now please??

Thanks, it turned out to sorta be the opposite of a clogged jet. Too much gas as opposed to too little. I'll ride to LG with you, but no freeways ok?

Fixing my carb seems to have made my bike run much smoother and I can hit 80kmh no problem now. Havn't gone on a longer ride yet to see if the "stuttering after extended top end" problem is still there.

Still havn't figured out how to do timing on one of these yet. I don't even know which part to adjust, is there a distributer? Sorry Nicky.

Not sure if it's been mentioned in the thread yet, but, how about posting a more descriptive thread title in future?

https://modernvespa.com/forum/topic28375

*cough*

you are becoming quite the scooter mechanic!!!

no freeways man, we can just cruise up Saratoga/Los Gatos, Sar/ SV, Hwy 9, De Anza...whatever you wanna call it..nice easy peasy ride..

I think the flywheel has to be pulled to adjust the timing

my title stated both that my bike quit, and that i didn't know what was wrong with it. sums up my OP very nicely thank you.

and my title is distinctly different than a "help! omg" title!

yea, title said it all..I guess you could of said "my vintage scooter stopped running, does anyone have any suggestions on how I can get it going again" .whatever..the scooter is fixed!!! woohoooo

Ask and ye shall receive ... here's my favorite "how to" guide for timing.

The engine he's working on is a GS/SS, which lets you remove the flywheel FAN and not the points-cam part ( it's a two piece flywheel as opposed to the 1-piece on your smallframe )

But all else remains the same. Pull your flywheel and have at it. ( oh, also - you may have your HT coil mounted on your stator plate instead of in the external brown plastic unit like in the pictures. you'll reconigize it on the stator as the coil with a big sparkplug wire coming out of it. You can tap in to this coil further upstream at the junction box where it ties to your wiring harness and on to your kill switch 0

http://www.kavsud.com/vespa/maintenance/points_timing/pointsTiming.htm *flexes* I should really start charging for online troubleshooting on a per-incident basis

cooool!! thanks AGAIN eric!!

Doesn't seem much different to me, but, whatever