Modern Vespa

I put a new battery in my scooter the other day. Got interrupted and lost concentration. Hooked up + and - backwards. Turned on switch and horn, lights and turns worked as they should. The next day I drove it a couple miles to warm up for oil change. Next day battery was dead. Corrected + & - and gave it slow charge.

Now it won't start. A mechanic told me to disconnect ground at the coil and try to start it. Sometimes that works and it will restart a couple, three times but won't stay running. I see spark in my inline tester and when I ground the plug on the engine. But it mostly refuses to start or stay running when it does start.

Any ideas as to what I screwed up and where to start on this. Thanks

The battery only controls the lights and horn. I doubt it will hold a charge again. Try and charge it but if it doesn't last, you know the culprit.

As for your ignition, the first thing is to find your CDI box. It's on the back of the engine and has 4 small wires going into it and one big wire coming out of it to the spark plug cap.

Check the 4 little wires. Make sure they are secure into the CDI box and the colored insulation isn't melted. If still looks ok, unplug the second green wire and see if it runs better. If yes, you've melted wires in your harness or key switch. If no, it's either fuel/carb related or something deeper inside the stator plate.

Thank you, Will check it out.

OK, I tried it wth both green wires off the CDI and it was a no go. I can get it to run with just the green wire off that goes to the kill switch. Won't run very long that way, 5-10 seconds maybe 30 seconds once in a while. I'm afraid it's a deeper problem than I can deal with. I will try to get the lid off the control pannel and see if there is trouble visible.

You definitely have spark, time to check gas. After it dies is your sparkplug wet or dry? While it's out you can check color & condition and verify you have good spark by kicking it over while grounding the plug. I'm guessing probably dry, if so pull the carb cover and filter. Drop a spoonful of gas down the carb and report back w/ results when you try to start it.

Can your fuel tap be closed (but not fully closing)?

(stupid question, I know, but...)

it seems to flood easy when I try to start it. Carb bowl was full when I checked it. I will check the plug the next time it dies on me. I wonder if I don't have a stator problem or intermitant wire in the harness.

http://www.vespamaintenance.com/

Since we don't know your background, please use the link for troubleshooting.

Do you know how to clean the carb? Know how to remove the flywheel? Know how to use a multimeter?

Thanks for the link. Will give it a look. Carb has 400 miles on it but could be fouled i guess, no ethanol. Haven't pulled flywheel ever. I have changed out cylinder/piston in chainsaw. Fairly good with VOM. got some other irons in the fire so i will move along at it as best I can. I think I'm due for a new harness as the lights go out when I turn all the way to the left. Not sure I want to tackle that. Also do maintenance on engines like valve adjust, points/condenser, etc., but not really a mechanic. I can do starters, alternators, change out radiators. I'm over 70 and I dislike that sort of thing more and more.

There is a green wire running from your CDI forward to your ignition switch which grounds it to kill your motor when ignition is off. Just these green wires have a bad habit of crumbling insulation after only a few decades and grounding to chassis killing the motor, often intermittently . Disconnect the outboard green wire on your CDI and I'll bet your problem goes away. There are TWO greens on the CDI and it could be the inboard one that goes forward if they've been switched.

Now only problem is how to turn off your motor... Usual solution is to just run one new green wire thru the frame to replace the bad one(the other colors are usually just fine ) , but easier said than done. Meanwhile, drop it into gear at a low idle and on the brakes, then slowly let out clutch. And Billyboy, age is no excuse, plus you will find these a LOT easier to work on than cars. I'm older than you so get after this and go for a nice ride after to put a smile on your face!

PM me for my phone # if you want a little hand holding.

Seems like you are more than capable of working on a vespa. Just need a second set of hands on some of the tight spots. The good thing is this can wait.

If your lights are turning off with handlebar movement, your harness, specifically the white wires, are probably frayed where the lower headset bolts through the fork. You could replace the harness, or have some fun with a soldering iron and replace a few frayed wires. The lights shorting will definitely kill any future installed battery. Best to avoid putting a new/charged battery in till you address that.

Carb cleanings are always a good thing so it doesn't hurt to practice! Better to be familiar with them now than on the side of the road scratching your head.

Thanks for the offer Voodoo, I may take you up on it. I did talk to a mechanic and he suggested the green wire removal at the cdi and that seems to work sort of sometimes. someone also said to pull the second green wire at the cdi and it was a no go. I checked resistance on the first green wire at about .3-.4 ohms subtracting vom line resistance. Could be intermittent which is killing it. This scoot has always been an easy start up, even after months of sitting. Started after a few kicks this spring. was ok till I screwed up the battery hookup.

I may have had the flywheel off years ago to replace the seal, maybe ten years. I had a shop do the other side seal. I have pulled the cylinder to check for coke and tidy it up a bit about the same time. Had a 66 180 super sport that I did a body and fender and paint, new rings, cables, etc.back in the late 70's. Sold it to get this P200. Should of hung on to that one.

Have to look at the link MJrally sent and look at the wiring diagram in the owners manual. Thanks much guys.

I got the stator pulled off and most of the wires are trashed. Got a new stator harness coming and the green wire to the ignition switch.

Can anyone tell me how the small brass blocks on the handlebar switchplates work. I can't figure out how the wire connections are made on the back side.

MJRally, could you elaborate on the lower headset bolt and where/how the white wires are accessed.

Many thanks

Don't remove the wires from the back of the switch! They go to the junction box behind the horn cast. Disconnect there.

You need to open the headset, disconnect the speedometer cable from the Speedo and then disconnect the front brake cable down at the hub. Remove the steering bolt (13mm socket) from the lower headset. Then pull up on the lower headset and fold it back towards the seat. You should be able to see the white power wires which go down into the frame. When in doubt, take pictures with your phone of every wire before you lift the lower headset!

MJRally,
I got the plastic headset cover opened and the horn cast off. The rotted green wire to the cdi and the kill switch are "y'ed" at the horn cast junction box. Thought I could pull the green wire to the kill switch through the wire loom if I knew how to unhook the wire at the kill switch. No idea how that connection at kill switch was made. But I can live with just a new kill wire to the ignition switch.

I was confused by the terms "lower headset". If I loosen the 13mm nut below the headset will the handlebars lift up? I know wire and cables will no doubt have to be disconnected. The reason I ask is I think turning to the far left has cut into lighting wire and shorts them out just below the headset.

Thanks for your efforts!

The switch you will have to get creative with but unsoldering it from the back of the switch would be my last resort. Try soldering in some new wire anywhere else first.

You MUST remove the 13mm bolt AND disconnect the Speedo cable and front brake to proceed. Then yes, you can lift up on the "headset." Might be stiff but it will come if you do the above 3 steps. The rest of the cables can stay as is. Try and then report back.

I got the stator rewireded and a new green wire pulled to the cdi. Used an old cable case to fish it thru the tunnel. Got by without pulling the foot brake. Mighty tight getting the casing down thru the headset. Also got the green wire over to the kill switch. Looked all over modern Vespa hoping for guidance and found a guy actually screwing in new wires on you tube. I had tried earlier to unscrew the posts on the front of switch but didn't want to break it as I was using a small vice grip. The screw slot is gone. Then I got forceful and got the wire released and the post was broken off. Tried to solder in new wire with 40 watt and no go. Then I drilled it out and used a 140 watt gun from the front on the brass block. Quick on and off and it's good.

Will try to pull the headset a bit and see if I can find the lights out fault next. Need new stator screws and tires coming.

Anyone know how long brake and clutch, shift cables last? Sure it's driver style dependent but curious what folks are getting for mileage on cables.