Modern Vespa

The double nut would have to be on the adjuster side, where you can already use the nut this way. It was corroded like so many other things in these cases.

I have cut a notch in whichever end was protruding and then backed out with a flat blade screwdriver when this has happened to me.

Today was gear cables and electrical cleanup. Also bashing the flywheel cover into submission for about 1/2 hour to make it fit. I had to replace one gear cable as it frayed going into the selector box. Stealing from my road spares again…

Really all that needs to happen on this engine is fill the oil, shorten one new gear cable to put the lid on the selector box, and kick start it. I don't have a shroud yet that fits - I had ordered one in my Mercato order but it was on hold waiting for sip to get stock on that junction box. I called last week and figured it out with Dave - so we went ahead and did the rest of the order without the box. That still probably doesn't put the box into my hands this week though, as there are a couple other SIP order items in there.

Have you got your junction box yet?

nope, they were out of stock and it was holding up my Mercato order so I told them to forget it and get me the rest

The little black junction box for the stator wires? Think I might have a stock spare one lying around.

Thanks - could you check what you have? It needs to be like below, if you have one. Center exit on the front side and outside exit on the rear side. It's for non-electric start PX, a rear beast in the USA.

Yup! We might be lucky!

Let me check! I might have it in storage, which might be a weeks wait, or we might be lucky and I have it with me in the tool shed.

I definitely know my local guy has one… literally on the floor not being used.

I'm using a 3D printed one, just more space for the vape wiring, so can pass you my spare

I'm pretty sure I have a spare one like that, too. I can check if 108 doesn't have one handy.

You all rock, now if I could just get the rest of that order already….

Was going for first start glory today but struggled mightily. First was no spark. The stator is a used item from Greasy, the flywheel a leftover from my P200. Swapped CDI's, no love. The flywheel was swapped for the one on the Stella engine and seemed to make some spark but still didn't start. Swapped the stator as well. New plug went in. It started but didn't want to rev out at all. Seemed to flood way too easily. So off came the stock exhaust that I had used and on went the Sito that was being used with the Stella engine. It wouldn't idle well until I swapped an undrilled filter for a drilled one. Now it would rev out, but if you stopped the engine, would flood again if you left it for a bit. I took off the float bowl cover - the float is OK, shot some carb cleaner at the needle and seat and put it back together but no real improvement.

It looks like time to swap carbs or at least float bowls. The engine has good compression and sounds OK as you rev it, so it's just a bolt on item, I guess. Based on all the swaps, the freebie SI20 I got in my parts exchange is looking suspect.

I need it to run right, then I can go back through the parts pile and figure out what to do with these by swapping them one at a time:
-suspect stator
-flywheel probably needs remagnetized
-stock exhaust is likely plugged
-filter - likely OK for the right application, just not sure this is it

I'm thinking some of this stuff is going to become automatic replacement in future rebuild. Was trying to see what we could make of the stuff I had but honestly it's probably not worth the effort on electrical....

nice that you made a little headway! which used stator was it that I pawned off on you?

It's a PX AC stator. I knew used stators are basically a gamble, but I rolled the dice. I will try it again once I sort the crabby carb. I'm honestly wondering if the pickup isn't lined up right or something. It all ohm'd out OK.

I felt kind of dirty putting that POS exhaust on there in the first place. I'm probably just going to chuck that. My guess is that pipe also filled with water like the engine while it was sitting and it's full of rust inside.

Yeah I was frustrated but realistically the engine build seems OK. It's really handy having a spare engine will all known good parts sitting on the side. I will order whatever I need to to make sure the spare engine stays with known good parts.

I don't get it.

I now have the same stator, flywheel, exhaust, CDI, and carb from my running engine. It won't start. If you kick it enough, and then hold open the throttle like it's flooded, it eventually starts but runs like it's flooded. The engine was pressure tested OK. The cylinder makes 120+ psi compression. The arrow on the piston points at the exhaust.

How can it not run????

Fuel, spark, air, compression.

You have compassion, so that's not it. Air is kindve a given with commission.

Check spark with a plug grounded you the case.

Use starter fluid instead of fuel. If it fires, then it's the carb.

You know this, you got this.

Yeah it sparks against the case no issue.

Fuel is definitely getting in there, there was a haze of fuel when I pulled the head and the piston is wet.

That's the thing, it seems like I have fuel, spark, air, compression. Wtf?? There's no filter on the carb and the exhaust is known good. Air kinda has to be there, doesn't it?

Starter fluid idea is interesting...

Old gas?

It seems the gas is likely from July.

Old gas could be an issue. Starter fluid is great because it covers all the fuel and carb issues, which means you now know the issue if it fires up with it.

Change the plug? Hmmmm....

Did try a new plug already.

Hmmmm. Green wire kinda shorting out? Hmmm

I'm really curious to hear what fixes this. It's a mystery....

Is the spark hot enough? I had a loose plug end on the wire that would spark, but not start.

I tried with the known good cdi/wire/cap, it should be. But I like how we are thinking out of the normal box here.

... and timing. Check the timing.

I can make marks to check timing but if it doesn't run it's hard to use them. I set it to IT for now. That worked well enough on the Stella engine with these parts. Any suggestions?

Green wire was fine on last engine and I've tried it disconnected just in case.

Did you try starter fluid yet? I always feel kind've cheap n' dirty resorting to it, but it's a great troubleshooting tool all the same.

I've got to reseal the head and then starting fluid is next. Lots going on though, so it may be a little bit.

A while back I had a similar issue to yours. I would check for spark and spark was good. Tried to start it and wouldn't start. New spark plug, and still wouldn't start. Robbed a known good CDI, stator, flywheel, carb, etc off another Vespa and still wouldn't start. At this point, frustrated, I gave up for a few days. I finally decided the only thing I hadn't taken off the known working Vespa was the spark plug. Put it in and started right up. Turns out I had a pack of 4 new NGK spark plugs that were all bad. They would show spark when you checked, but wouldn't start when in the cylinder head. Not sure if this is your issue, but thought I'd put it out there. Best of luck figuring it out!

thanks Langolson - definitely worth checking, I've got different plugs around from different times, so will do if the starting fluid test fails.

cylinder head back on with copper spray a gasket, will try to fire it later, hopefully. if not, then tomorrow.

I'll second a plug change as a just in case.

if that fuel is from July it's suspect for sure. like CM said, starter fluid or even carb/brake clean should sort that right out quick.

you're right there, it's just a hiccup!

update:
starter fluid makes no appreciable difference. i assume that means the carb and gasoline are probably ok. doesn't it mean my problem is ignition?

plug removed from stella engine and put into the PX125 engine, no difference

green wire from harness removed, no difference

what gives? I have all the components from the running engine onboard and it won't run.

i'm thinking along socalguy's ideas now - is it possible the crank key is in the wrong location, putting the timing off? is it possible the stator is 120 off? I don't think so on that one, the stator timing marks and case timing marks are together, set to IT.

is it somehow possible the plug won't spark in the head but is OK out of it? if so why?

I was thinking maybe the piston is stamped wrong for direction but the ring pegs were on the top side where they belonged. I don't think this can be it.

You can get a visibly good spark from a bad plug...even if that plug is brand new. Many knockoff NGK plugs (and many other brands too) are sold on ebay.

quick thought, is the Stella flywheel external trigger and the PX is internal?

beyond that, I think there's a ghost in the machine...

Weird. So it still starts eventually but won't rev? Or won't run at all? Is it a Stella with reeds?

With much effort eventually it can sort of run but wants to stall. It will rev once you get it there. It acts like it's always flooding.

It's a px 125 with all px parts. To be clear I was running all these parts on my Stella engine - I've gotten rid of all the Stella specific parts a long time ago as far as ignition goes.

I'm thinking now to advance the stator a lot - I'm at the far end of the slots in the retard direction. Since it can run maybe it's just super late.

I had the flywheel slip (always use a torque wrench... ahem) on my white P rebuild and it went all pear shaped...

Pull the flywheel, (assess timing marks again but don't make drastic changes unless you were obviously wrong the first go around), new woodruff, reassemble, torque to spec.

Yeah I'll look at that when I pull it to advance it. My idea is to make it run well enough that I actually can make marks and check timing appropriately.