Modern Vespa

Last ride I had two nearly back-to-back soft seize events. I never had to stop, just hit the clutch, slowed and got it restarted and kept going. Afterwards I'm hearing the dreaded jingling sound, but I haven't opened it up yet to inspect for damage. It rode fine for the 10 miles back home, with normal power, but I did limit top speed.

I would appreciate any comments on my current set-up and tell me if you see any obvious adjustments needed.
Pinasco 177, iron cylinder
Spaco SI20-20D
40-130
160
BE3
116
B8HS plug

Your jetting is too lean across the entire range. Idle, Air corrector, atomizer, and main all need to be richer with the Pinasco.

You need to go up to at least a 55/160 or 52/140 on the idle, a 140 AC, BE5 atomizer, and a 120 main just to get in the ballpark.

You probably have some aluminum from the piston smeared onto the cylinder. You can clean that up with muriatic acid, which will attack the aluminum but not the cast iron.

You should also check for air leaks, probably a head leak at the minimum, and ideally pressure testing after you get it all buttoned up just to be certain.

The Pinasco is a pretty bulletproof kit overall, but the port layout and piston leave a lot to be desired stock. Definitely needs the windows in the cylinder skirt opened up significantly because they just flat-out don't match. If you fix that, the jetting problem will be even more significant, so be aware.

Your timing may also be too advanced, preventing heat from exhausting correctly, so make sure your timing is set to 17 or 18 BTDC (assuming static ignition).

Post some pictures once you get it apart of the piston, cylinder bore, head, and spark plug. That'll confirm or refute my initial diagnosis.

Your 40-130 is too lean. The 116 Main jet in my opinion also lean. I am running other kits but I am in the 122 main jets and 55-160. One has a 20-20 mm carb and the other a 26-26mm.

Thanks for the replies so far. I have a small collection of brass from Tierney...
55-160 idle jet
E1 mixer tube (Only says E1, but I assume this means BE1?)
and mains 108, 110, 112, and another 116, unfortunately nothing higher.

My understanding is that you divide the two idle jet numbers, so my current 40-130 would be more lean than this 55-160, so it makes sense that I need to swap in the 55-160 if I wanted to richen the idle. Is this right? But it starts and idles OK, so no need to mess with the idle to try to correct this problem with running lean at high speeds, right? Or does the idle jet also factor into the high speed mixture?
I understand that my BE3 is leaner than this BE1? So I guess I need to swap in the E1?

So I guess I need to order some mains, maybe a few sizes in the high teens and 20's? What about the air corrector, should I change it also?

There actually *is* an E1 atomizer, though they're pretty unusual. It will be richer than the BE3, though, along with the idle.

You should definitely switch to the 55/160 idle if you want to avoid seizing. Even if it starts and runs okay, when the engine returns to idle when it's hot, that when you'll seize it with a too-lean idle.

And don't thrash it until you can get some richer main jets. You want to start rich enough that it won't rev out, then work your way down. Once you find the jetting that seems revviest, go up one jet and that's where you want to be.

Oh yeah, that makes sense about the idle jet coming into play on roll-off! OK, so I'll go ahead and swap in the E1 and the 55/160, and order some mains. What about the AC, should I change that also?

I made the jetting swaps and pulled the cylinder. There is some mild transference of Al onto the cylinder walls. Surprisingly, the rings look OK and are still free in the piston grooves. I expected a broken ring because of the jingling sound. So what's causing the jingling noise? I still heard it loudly when I ran it for a few seconds after making the recommended jetting swaps.
Where can I find info about opening up the windows in the cylinder skirt that chandlerman mentioned in his first response?

I have a super important question. What oil are you running? since I switched to Motul 710 I haven't had issues withs soft seizes. A good 100% full synthetic oil will make wonders.

On a side observation, what I am about to say it might sounds retarded but you can tell when a engine is running hot, the iddle tends to be erratic, you feel lack of power and you can feel that intense heat and smell that hot air. Been there done that and I can also say that the air mixture screw has a lot to do with everything as well.

Touches a bit on what porting is, longer and shorter videos.You can match cylinder to base and piston to cylinder. I think what Chandler is talking about is holes or ports in piston aren't as big cylinder or aren't aligned. Gas flows through inside of piston to cylinder. Sometimes manufacturers don't do a good job of matching the two.

https://www.google.com/search?q=vespa+pinasco+177+porting&source=lnms&tbm=vid&sa=X&ved=0ahUKEwiE7YyIsP_3AhXds4QIHXBzAfgQ_AUICCgD

https://www.google.com/search?tbm=vid&q=vespa+o+tuning+cylinder&oq=vespa+o+tuning+cylinder&aqs=heirloom-srp..

Yes, you need to go down to a 140 Air Corrector. All the jetting recommendations are aligned to that. The AC controls how much air gets into the jet stack, so it's like a multiplier for for the atomizer and main jet.

And if you want to learn about porting, I've done a couple project threads where I got into great detail. Porting 101, was my first porting adventure, so I asked LOTS of really basic questions asked and the forum helped me out tremendously.

My 1976 Sprint V mechanical rebuild
thread will be useful to you because it covers the porting work I did on a Polini 177 (along with a bunch of really basic intake timing stuff).

Those should be a little light reading to get you started, and then you'll want to learn about pressure testing once you get it back together--you'll never get it tuned right if the whole setup isn't airtight.

I'm curious; what is the dreaded "jingling sound"?

On my 62 Allstate, same kit, it was the piston skirt taptaptapping the warmer it got. I did all kinds of shennanagons to get rid of the issue but to no avail. It all started after a couple of soft seizes when I veered far away from Jack221's advice.

I started with a new kit (Piston & Cylinder), and my jetting is as follows:

120/BE4/132 with 45/140 idle jet. 24/24 carb, drilled to 2.1mm. I've run this for 500 miles and can run it WOT and the temp stays just below 300F.

The one thing that surprised me is how high I had to jet this thing to keep it below 300f. It's a different beast than a 200cc machine, that's for sure...

I just received my order of brass from Scooter Mercato!
Main jets 118, 119, 122
Air Corrector 140
Atomizer BE4

I'll install the BE4, the 140, and start with the 118 I suppose.

No. Start with the 122. Work your way down till it doesn't sputter at WOT

OK, yeah, that would be the safer way to do it.

Yep. No sense soft seizing yet again right?

Naw, two rounds of scrubbing lye off my hands is enough.

What air corrector?

Update: I cleaned up the cylinder and it's all back together with jetting...
55-160 idle jet
140 AC
BE4 atomizer
122 main

Initial observations are that it feels OK at WOT (briefly because I'm seating rings again). But at mid speeds, steady-state cruising with maybe half throttle its breaking up and surging. Maybe too rich in the mid-range throttle?
I stepped down to the 119 main, and noticed no real change at full throttle and the mid-range surge /break-up was not changed.
I stepped down to the 118 main, full throttle improved this time, but no change with the mid-throttle surging.

Should I perhaps swap the AC or atomizer to try and improve the mid-speed/mid-throttle condition? In my collection I have...
160 AC
E1 and BE3 atomizers
40-130 idje jet

Which size main jet causes wot to not rev out?

If a 140AC/122 main is correct, then the BE4 may be too rich. Try the E1, which I think should be about a BE5, see if that sorts out the mid-range, but I'd feel a lot better if you knew for sure that a 125 or 128 was too rich.

Did you work your way down to the 122, or start there and say "good enough?"

My collection of main jets consists of 108, 110, 112, 116, 118, 119 and 122.

The spreadsheet in this thread is interesting...
Which atomisers for the SI carb are leaner/richer?

It seems to indicate that the BE3 would lean the low-range AND richen WOT, compared to my BE4. It's easy to try, just takes a couple if minutes to swap out, so I'll give it a shot.

So you recommend that I order some richer main jets just to test with? Jack221, It would fully rev out with the 122, so that indicates that I haven't found the "too-large" jet yet. I started with the 122 per the suggestion above, then worked down to 119 then 118.

Working down the main jet means, finding the jet that doesn't rev out. Then walking the size down until the jet size is found where it just about does rev out ok.
Not fit a jet that revs out, then walk it down in size until the engine seizes