Modern Vespa

I tried firing up the Sprint today ( it's got a P200 engine in it) and it started up after about 4 kicks, not having been used for a couple of months. Ran well for 5 mins, But then suddenly, it stopped. I checked the fuel- no problem it still had half a tank of fuel.
Took off the spark plug, and noticed no spark, checked the HT lead, no issues there, checked and swapped the CDI unit, checked the regulator, popped in a new spark plug, still nothing! I reckon it could be somewhere damp, but where else should I check??

Puzzled!

Graham

Try disconnecting the green kill lead going to the CDI from the handlebar. If you have spark, it’s grounded out somewhere in the frame.

You can also check the stator plate ignition charge coil and pickup coil. Disconnect green, red and, white wires from the cdi.
Check the resistance with an ohm meter. Between the green and white wires should be have 500 ohms, plus or minus 20. Between the red and white wires you should have 110 ohms, plus or minus 5.
Hope this helps.

cheers for that! I'll check over it sometime today, when I get the chance, I suspect damp has got in somewhere and shorted it out, The scooter is due to be stripped and re- painted in the next few months, I might invest in a whole new wiring loom, as this wasn't the first of many electrical problems to develop in the past year or so!

Graham

When you check the red, white and green CDI wires give them a pull, see if they are broken inside.

Bugger checked the wires near the flywheel and checked the stator plate and read the measurements as advised by Robot and they were right on the nail.... The stator plate was in really good condition, in fact, it was replaced a couple of years ago!

Checked the white, red and two green wires, and they looked in good condition as well. I have a Ignition switch fitted in the toolbox panel inside, with a key, and that seemed ok as well, as were the wires going to the rectifier..

I'm thinking of checking the handlebar switch next, and I know they are a bit tight in that area, but it's bloody freezing here in St Neots, So I'll check hopefully tomorrow, but is there anything else to check? It's a standard Sprint Veloce, with a standard P200 engine, so It should be fairly straight forward.. Any clues???

Cheers

Graham

don't go for the switch

so long as you've got the frame lead to the cdi disconnected (one of the greens) then the switch is irrelevant. you will just be wasting your money and time if you can't get the bike started without the frame lead attached by diving into that rabbit hole.

if you are still getting no spark and have a flywheel puller, make sure your flywheel magnets can hold up a 17mm wrench. you could either have a demagnetized flywheel or maybe something has gone wrong with your pickup. my vote would be in these 2 areas as they are the next most common items being that you've tried a new CDI and plug. did you try a new wire and new plug cap? I wasn't clear on that.

yep, tried the flywheel with a 19mm spanner, and they held well in four places around the flywheel, and I swapped the CDI, and the sparkplug with cap, and I still didn't get a spark. Funny, as when It was first fired up, after sitting for a couple of months, it ran fine for about 5 mins, and then cut out. I thought it went on reserve, but it was a spark issue...odd...

Graham

did you make sure the tap is good and fuel is actually reaching the carb / entering the engine? I assume so, you've done a pretty good diagnostic tree here.

I'd go with pickup or LT coil at this point if you're sure the fuel is getting in, get both and start with the pickup.

Yep, fuel is good, flows really well, but there's no spark at the plug. I'm hoping to get the scooter re-sprayed in the spring, So I'm going to order a new wiring loom ( the stator plate looks new) and completely replace the wiring..

I've checked everything over, I can't think of anything else to try, so I'll put this job on hold until the re-spray!

Graham

if you've got continuity between the red, white, and green wires at the stator and the CDI, and no shorts, you have a problem in the stator. Don't go throwing the baby out with the bathwater here. It's likely your pickup, they fail often.

I ran over a multimeter today and the results were-
Continuity betweeen white and frame -02
Green-white - 460 ohms
red-white-93 ohms

could this be an indication the stator is kaput??

Graham

try looking here:
Stator Values Wiki

White to frame/engine case should be a hard ZERO. No resistance. 2 ohms is pointing to a bad ground somwhere and CDI system become pretty iffy without a good ground. Indicative of the fact the CDI unit itself has TWO grounds, the white and the pigtail.

Hope this helps.

What's the resistance of your two meter leads by themselves connected together?

0.2 when both the leads are together I've ordered a new stator plate, as I think the pickup could be faulty, and it'll be easier to replace the whole lot, rather than repair a possible broken stator plate

Graham

Don’t know if you have a spare flywheel but throw that on for giggles while you wait for the new parts.

Got hold of a working stator plate, fitted it up, lined it up correctly and wired the cables - nothing...

No idea what to try next, but as I said earlier, the scooter is being resprayed hopefully in the spring, if this bloody lockdown ends, so that I can take the frame/parts to the sprayer! I've bought a new wiring loom to match the engine (P200) so that I can re-wire the scooter, and have another go as to why the bloody thing doesn't start, when the frame comes back!

Graham

so why not pull off the carb, clean it, and try again? did you say for sure that your plug gets wet when it doesn't start? it's so quick and you've done so much on the ignition side already.

along a similar line of thinking, throw a compression gauge on there, it only takes removing the plug and a few kicks to feel good that your compression is OK.

it just bugs me that this hasn't been sorted yet!

air, fuel, spark, compression are all that are required. plugged exhaust??