Modern Vespa

I wonder if the vortex is making it run lean. Might need bigger main jet. I don't know what else to do.

Key is for alignment only, flywheel and crankshaft are supposed to pull together when tightened down and wedge into each other. That's the pop you get when using a flywheel puller. You need to lap flywheel to crankshaft and make sure they are torqued to spec.

I think I may have not tightened the nut tight enough. I forgot to check the torque. My bad.

The flywheel key is there only to position the flywheel correctly on the crank. If you have a sheared key, you have a bad contact with your cones.

Clean out the edges of the keyways on both parts with a small file if they have deformed. Then apply some fine valve lapping paste on the taper and spin the flywheel back and forth on the crank to lap the cones together. Clean up, apply sharpie on crank cone and spin the flywheel again to see if there are points where contact is bad. Rinse and repeat until good contact is made.

There is something not right here. If you go up to a bigger main jet it could tell you how bad the issue is but there is an issue.
The usual is the fuel flow isn't fast enough from the tank.
Can be the carb bowl drilling not big enough (BGM kits are not as powerful as yours).
Could be that your 138 main jet actually measures much less.
Plenty to think about but if you can't get it to choke at WOT its not safe.

I will take off the carb and take a look. Might even fit my Pinasco Chamber Cover and check the chamber hole is at least 2.5mm. Job for today. The main jets are all bgm. Part of a kit I bought.

If it where not getting enough fuel, would it not cut out at high revs. I am confused how this works. I understan that it will bog down if too rich but not sure about when its too lean. The plug was dark and seemed wet when I took it out to check. This is the carb https://www.scooter-center.com/en/carburettor-bgm-pro-faster-flow-dellorto/spaco-si24/24e-vespa-px200-type-with-autolube-bgm8570?number=BGM8570

Too lean is the big one. Mild to moderate lean perform fine and can almost go unnoticed. Wear just increases and reliability plummets.
Very lean will seize and extreme lean will hole a piston.
From ideal, lasts forever, to lean is usually just one jet size. For perfect jetting the window is narrow.
Need to check the bowl drilling on your carb. Should be at least 2mm. Some BGM carbs are only 1.8mm.
Use the AC120/BE4 jets from the old carb. If you use the BGM ones it will get damaged.

I have drilled the carb out to 2.5mm and fitted the pinasco chamber cover. As for the jets, I have always used the BGM ones so have that baesline to go from. Once the flywheel key arrives I shall check it all out again and go from there. In your expert opinion, what main jet range should, should I be aiming for. I thought it would be around the 128 - 132 area.

According to your link AC would be a 160, there's also a note in that same link.

NOTE
Modified (drilled) air filters or air intake funnels always require richer nozzles due to the better working air correction. The intake funnels (also called venturi) may need a main air correction nozzle that is smaller and therefore has a greasing effect (e.g. 140 instead of 160).

Main jet performance is relative to the air corrector. With an AC120 the main jet should be 125/130 or so. With the BGM AC160 something like 150 main jet. The air corrector is for sure the most important part when the undrilled stock filter is removed.

I will always use the 120/BE4 as you said with no filter and no carb box cover. I will update next week. Thanks again. It won't run with the carb box cover on. Revs drop and its really boggy.

Once you find rich, fit your vortex bell if it's not on already.

It's fitted already. May be best to take it off like you said and find the rich point then fit the vortex. I will give that a go too.

Well that explains a bit. No stock filter because you have a vortex in the same position. However, the SI carb needs to be in the box, with the lid on at all times, even between jet changes. The bellows should also be connected between the box with lid and the scooter frame. The jetting is sensitive to these changes.

Next time out AC120/BE4/138MJ lid on, bellows on and hopefully it chokes so bad its unridable.

The vortex catches the carb lid and does not fit properly. Stalls as soon as I put in the lid. Bellows always fitted. Might have to remove vortex to fit lid properly in which case it was a waste of money for the vortex. Lol.

Take a close look and see what is catching, maybe just a little adjusting to get it to fit? It's worth taking the time to do a little adjusting, and use it. Like I've said previously, I can't believe needing to go up 10 jet sizes isn't creating more power.

Even when I fit the lid without the vortex, the engine slows down at idle and is really boggy. Can't seem to win. Maybe it's too rich at idle. May have to adjust mixture screw.

This is why it all doesn't make sense. With a 138 is should be bogging. Really bad. This is where jetting starts.
Cover must be on at all times. Vortex must be on. The more variables the more complex. And by complex I mean well still be doing this is six months.

What I can't fathom is why putting on the carb lid, even without the vortex chokes the bike. I have checked the bellows and they are not blocked. The hole under the seat is also clear. Just what is going on?

The entire intake was made to move enough air for a 13hp motor being generous, mildly tuned you can easily be in 18hp range. Putting air box lid on creates vacuum which changes tuning. I think you said you purchased a Pinasco box top which moves top away from carburetor intake and that helps.

The bike came with Pinasco Fast Flow chamber cover. I am still running the original carb box lid.

You may want to get one of these, helps it breath better, your vortex might fit better also.

https://www.scooter-center.com/en/carburator-box-cover-air-intake-filter-pinasco-airbox-vespa-px-efl-p-range-1984-7675217

Means spending more bloody money though. Why has this not been mentioned before? I honestly feel like selling the bike as is and letting someone else deal with it, who knows more than me about them. It's now quite apparent that this kit needs some special attention. I sort of wish it didn't and I had chosen another kit. I could understand the upgraded box helping at high revs, but not a low revs.

No fancy lid is needed. Just put the original box lid on and start riding. Spluttery is good. We can work down from there.

May have to remove the vortex as it is almost touching the lid when I put it on. Hardly no space at all.

Don't worry about it. Just get riding.

Your carb height, vortex height and box lid are all exactly the same as mine on my P200. Plenty of space.

Ok. As soon at the clutch cable arrive and flywheel key, I will put the lid on and try to ride it with the 138 main. I will report back on Sat.

The vortex on mine touches the lid and does not fit properly at all. The rear of the vortex touches the box and does not seat right. I will take some photos at the weekend and upload them.

Does your carb lid not catch on the vortex at the rear? If not then it can't be the same as mine. Something is amiss. I am going to have to remove the vortex for the lid to fit properly. No point forcing the lid on as the vortex will contact the top of the lid and have no room whatsoever. Then it will definitely not run properly. Might not even star due to lack of air. It runs shite with the lid on. I don't know what the fuck is going on.

Something is not fitted correctly. All the parts we think you have fit together. Some pictures would be a big help.

I will upload some photos at the weekend. Get to the bottom of this.

So I asked for a bit of advice on Facebook and a guy called MistaFreakMoped recommended I used a 160/BE3/130 setup for this kit, similar to the T5 and P200. This conflicts with the info I have been given on here. So, who is right and who is wrong OR is everyone right a little bit? He suggested that the current 120/BE4/? is for a Si20/20 carb. I have noticed that my carb lid has a metal tab on it. Others I have looked at on the web don't have the tab. It's like a little bracket.

On these things there are no right or wrong aswer over the internet. Just good guesses backed by experience.

What works in Vienna might not work as well in different altitude, rh% and temperatures. Also all these old engines are individuals with various levels of wear, different configurations etc.

These things just have to be tried out.

So got home and started up the bike. Runs like fucking shit. Idle seems really rich. Mixture screw all the way in. Changed from 140 main to 120. No noticible change at all. Changed 55/160 to 50/something. No change to idle at all even with mixture screw fully in. Idle screw fully in and ticks over at max 1500 rpm. Changed air corrector from 120/140 and again, no change at all when revving. Still reaching 9000 rpm even with a 140 main jet. If I put the carb cover anywhere near the carb, revs drop and it stalls. What the fuck is going on. Loads of fuel mist coming from the venturi when revving from idle and I mean more than usual. Vortex makes fuck all difference too. Is it anything to do with the cases not being ported and its being overfuelled? I honestly think I have purchased the most fucked bike ever.

Sounds like this:

Edit: I see hec in Omaha suggested this on the first page.

Also can't remember, did you install this kit yourself or hire someone to do it?

Probably suggestion out of left field, but take the exhaust off and the plug out and peek into the cylinder from exhaust stub and rotate the crank to see if the piston has holes in it on the side pointing down towards the exhaust opening.

Piston port is inlet side.

You cannot jet these with the carb cover off

It's very smokey again. Surely the clutch side seal has not blown again.