Modern Vespa

for jetting suggestions - when asking give a refresher on what's on the bike, it's hard to keep up with all the jetting threads at the moment!

Just to recap:

Stella engine with 177 Polini kit, 20/20 carb, 22t clutch cog, SIP road 2, rebuilt with 60mm long stroke crank.

Jetting was:

Main-112
Mixer-BE4
Air-160
Idle-42/160

Summing up suggestions:

Main-118-120 (work down from 125)
Mixer-BE5 or BE3
Air-160 or 140
Idle-48/140 - 55/160

Thanks.

yeah the 140AC is safer, the start from 125 makes sense

the atomizers and pilot choices, I'm not sure, having never dealt with a 177 kit yet

Did the leak test again with some permatex blue snot on the base of the reed block and tried it with the carb box on. Success! It was still at 6 lbs a half hour later. I hate leak testing. It was a whole evening of dicking around.

I feel like I'm seeing the light at the end of the tunnel…again. I am finally getting some time to get this done without rushing anything. I booked my road test for the 27th. The missus has expressed interest in going on some rides.

For jetting, I will start with something like:

Main-125 and work my way down
Mixer-BE3
Air-140
Idle-55/160

At this point, my main concern is reliability. I like to take long rides into the middle of nowhere, so speed is a secondary concern.

I know I'm getting ahead of myself, but I am hoping to rebuild the 200 engine as a winter project. I would keep it pretty much stock with the exception of the Road 2 and optimizing squish, etc. I enjoy working on these engines, especially when I'm not under the gun to get a bike on the road. It will go on the P200e. I really liked riding with this engine.

BE5 is safer bet on the atomizer, and lean it out with BE3 if you can't get it clean

one of my favorites - read it all the way because people keep correcting each other and even themselves

Lets talk atomizers

Wondering what you did with the 60 mm crank. This was the right thing to do but depending on where the 1.5mm spacer is placed/divided, changes everything. With some kits the blowdown drops to dangerously boring levels.

I would start with an AC120/BE4 and work from there. It will splutter a bit but get the wide open sorted first.

This is what I ended up with for timings. Squish is a little much at about 1.8 mm. I may lap the head more to bring it down.

The thing that makes jetting so difficult is that recommendations are all over the place.

I'm guessing that different combinations can result in similar mixture ratios, so I'm just going to pick a combo from the many suggestions offered to use as a starting point, see how it runs and go from there.

Would guess the whole 1.5mm is on the base. This timing will go ok but won't be very exciting.
If you drop the cylinder base to 0.5mm to make the squish 0.8mm, the port timing gets sharper. Will pull higher gearing too.

If you start too rich with the jetting it splutters, no damage.

Since the piston was measured at .78 mm below the cylinder deck, wouldn't a .5 mm spacer bring the squish to something like 1.6mm?

Take off all others spacers and fit only a 0.5mm. Still guessing you have a 1.5mm there now, to achieve -0.78mm. Should end up +0.2mm.

Yes. It has a 1.5 mm spacer. This is what I get with a .5mm spacer.

Same numbers I calculated. This is the best you can get it, without any grinding in the cylinder.
What carb, gearing and exhaust? Are there options?

It's a 20/20 on an LML reed block with a Road 2. it's not port matched. I was happy with the way it ran before the LML crank gave out. At this point, just want something that goes down the road before it snows.

0.5mm base will be ok with the 20/20 and road II. You know what the gearing is? 22/68 would be good. 21/68 ok for now.

It has a 22t clutch cog. It seems that I can either have decent timing ls or decent squish, but not both.

You can if the cylinder is modified. For now 0.5mm on the base will go best.

It would be good to have a context for these numbers, starting with what are considered good timings. I know that it depends on other things in the combo.

A couple pages back, I actually bought some shim stock and made a .5 mm base spacer, but the timings seemed meh…

The recommendations you are giving suggest that optimizing squish is a better option. I do understand that a lower squish raises the compression ratio and improves the efficiency of the mixture, to put it simply. My understanding of this is from 4 stroke automotive engines…a big deck and low compression ratio will render an engine gutless.

Any good references for choosing optimal port timings?

10-4. +.2mm above the cylinder mating surface would indeed give me a squish of .8mm on a head with a 1mm squish depth from the head mating surface.

This is why I hate these things…

https://modernvespa.com/forum/post2493910#2493910

that's how i fixed my headset where both mounts were trashed

Thanks!

That's brilliant!

I also found these after I calmed down:

https://www.mcmaster.com/shoulder-bolts/system-of-measurement~metric/

I could get the same size or with a slightly larger threaded section. I think the headset will still support it even with the drill damage.

I was also bummed because I thought I had left my spare clutch cable at the old place, but I found it. It's different from the old one, but should work.

There are similarities between 2 and 4 strokes. Compression is one of them but on a 2 stroke squish turbulence is important too. As much as possible before it gets too hot is the right answer for higher power.
When making port timing decisions the whole engine set up must be considered and also what kind of power delivery is required. The port timing and exhaust work together. Either can be changed to alter the relationship to suit requirements. There is no actual best but for us pulling 4th gear will usually do. There are many books on the subject but all differing opinions.

Thank you. I think the difference of opinion is typical of tuning in general and often comes down to rider preference. Since my scooter is already set up, leak tested and ready to go with the 1.5mm spacer, I'm going to run it that way to get a baseline.

When I get the kinks out and have more time, I will try it with the .5mm spacer and at some point consider changing the transfers themselves. I think part of tuning is understanding through seat of the pants experience of how these changes effect performance.

I think that's why you hear about people loving and hating the same kit. It's not the kits fault that you didn't get what you expected if you didn't know what you wanted in the first place.

I ended up reading further into your thread. Really helpful because I am coming across many of the same issues. I fought with installing the clutch cable for ages only to find it was too short. Another one is on the way but I wish I had bought a new liner. Next time.

I also bought a new Piaggio Stator and CDI as I had intermittent ignition and fuel problems last time through.

Anyone know a source for led turn signal lights to replace bayonet style bulbs?

I agree, people kept telling me I needed to make change "X". When I started reading change X moved peak power further up
RPM range which isn't what I wanted or needed. Some people like tuning for peak power no matter the RPM. I had a cruising speed of 60MPH as a goal and worked around that.

superbrightleds.com or bulbamerica.com have led replacements for standard scooter size bulbs.

Ordered multiple times from both for various auto and PCB projects and both are good prices and fast shipping.

Thank you

I agree with the advice, it's just that it's already together, but I will definitely try the suggestions at a later time.

It's already together, see how it goes. If your port measurements were off are off by even a small amount it all becomes moot. Now the 1.8 mm squish, probably is 1.8mm. It will still run fine, see what happens, make good notes and adjust it in the winter.
If it pulls 4th gear and will roll on from low speed to flat out, call it done.

I made up a .5mm base shim, so I have one ready to go. The transfers are a little tricky to measure, but I think I eventually got them correct. I came across a thread with measurements and they were very close. I can see myself playing with timings in the future and I see the appeal. Time is running out for good riding weather here and my road test is at the end of the month. Even if it's a dog, I will be happy if it gets me through my road test.

I was back at the other house and found a complete set of new cables in my parts stash after ordering a bunch. You can never have enough spares. I also threw my welder and cart, air compressor, mechanics drawer set and the P200 in my bus and drove it to the new place. Have I mentioned how much I love my bus?

Actual question:

I have a new PX stator and CDI arriving today. How do I float the ground?…as in which wire goes where. I think I had it hooked up incorrectly with all the tinkering I did and reinstalled the ground that had been floated. I am running a DC only system with a Trailtech regulator.

Thanks

This is my new Stator. The ground is here. I know I should cut that one off, but where do I add the new wire to float it? This is a PX Stator and looks a little different than my Stella Stator.

Thanks.

Looks like the wrong stator. Shouldn't a Stella have a 5 wires stator??

To float the ground you cut the grounded end of the coils and install a second "blue" wire. Black stays, you need a ground…

That's how I do them…

Thank you,

It's for PX electric start, which is the closest thing I could find to the Stella Stator on the Mercato site. I see the ground for the coils is in a different place.

Someone, somewhere used this stator on a Stella, I just have to find the thread again.

I'm not certain my Stella Stator is faulty so I will run it for now. I had some fuel spark issues and wanted to have a backup just in case. I also have a new CDI.

So if I understand correctly, the bare wire I have marked is the ground for the coils. I would cut that wire, unground it from the Stator and solder on a new wire. That wire goes to the Trailtech regulator. Do I still use the black wire? I thought that it was usually removed.

To quote my dear departed Dad, "Close only counts in horseshoes and hand grenades."

The stator you bought is different from the usual found on PXs (5 wires). The one you got has 7 wires and it's wired differently (coils are in pairs and separate between pairs). I don't know it it can work for your circuit...

Post a pic of your old one...