Modern Vespa

For my 59 Allstate.

Went back to Jacks suggestions to start this all over. Started with a main jet of 136. Walked it down to 128 and 125. Is cleanest I think at 125. But still has problems.

Still have decel popping and 4 stroking.
Stack is 120/BE3/xxx
Idle 50/100 2.5 turns out. Can you guys listen to the videos and advise where the balls I gotta go to get this running properly?

120/BE3/128
50/100 2.5 turns
https://youtube.com/shorts/M-S0AiDIoYo?feature=shared

120/BE3/125
50/100 2.5 turns out
https://youtube.com/shorts/WE7HlfkNhJA?feature=shared

Since I still had decel popping I moved the mix screw to 2.75 then rode home as I ran out of time/patience
120/BE3/125
50/100 2.75 turns
Thanks for any and all help.

This a 24/24 carb? Even 125 sounds rich. Pilot is definitely rich.

Temporarily put in a lean pilot. Something like 48/120 will be lean. Don't go cruising around the town on lean jetting! But it's OK for testing up the road.

With a known lean pilot all richness will be main jet only. See how 125 is then.

Yea, 24.24 carb. I have 60/160 and a 45/120 (2.67)which are roughly the same leanness away from a 48/120 (2.5) I'll pop one of those in tomorrow when I have time again. I'll also record the sound again. Will make this much easier I think.

Thanks!


Edit to list all the pilot jets I have on hand:

55/100
52/100
50/100
48/100
45/100
50/120 (didn't know I had this one)
45/120
60/160
52/140
50/140
45/140
38/120
40/130

60/160 and 45/120 are not roughly the same leanness. You're not thinking about the idle jet correctly. Go back to the beginning of this thread.

SI Idle Jet Quiz

I must not have absorbed that discussion as well as I thought. I even posted in there
Thanks for linking it. It was a great reread.
So the 60/160 would be the richer of the two with the same ratio? Since it's delivering the 60 over the other one dosing out 45 so to speak?

Not sure "richer" is the best way to describe the difference. 60/160 flows more gas but also allows more air.

Think of idle jets as the "120 group", the "140 group", the "160 group" etc …

When I'm hunting for an idle jet, I work my way there the same way I chase down a main jet. Start safe - with something that flows a lot of fuel and doesn't draw a lot of air, like a 55/120.

The mix screw is the yardstick. It tells you when you're in the ballpark. It adjusts how much fuel the idle circuit delivers. Turning it out, more fuel, turning it in, less. If all the way out doesn't make the engine bog at idle, go to the next smaller jet in the "120 group". Once you found that, find a jet in one of the groups with that flow that responds to turning the mix screw in.

Like he said. Not the same. The dividing rule defines a single richness value. Problem is the pilot jet operates in a varying pressure environment, hence richness is a curve.
Two totally different pilot jets might have the same richness value but this specific richness will not appear at anything like the same rpm. Therefore it's just confusing bollocks.

"Therefore it's just confusing bollocks."
Like so many things.

What was your issue before the start-all-over?

Decel popping and 4 stroking. Nothing I did got rid of it. So I went back to square one to start fresh.

Had a 60/160 idle with a BE5 and 120 main and it still did the issues. Mix screw in or out didn't matter.

Just need a fresh start to get it dialed. Plus I have some time to commit to it.

If you are starting at square one, what's your timing?

Got it.
60/160 will choke it.

Try your 52/140. It has magic powers at the level of tune as a baseline.
140ac/be3/XXX -- test for most power up a hill 3/4-WOT (no need to scream down a flat street).

Spaco?

Jon Gick set that up. Variable Vape. So I'm not sure on that but I assume it's correct to spec.

Yessir

Had no rain finally today so I got back to it and rode down to my spot with the 120/BE3/125
50/100 2.75 setup and once warmed up swapped in the 50/120 idle I have. All else is the same

Here's the WOT in 2nd test

https://youtube.com/shorts/jwlCmJ-HYQ4?feature=shared

And the ride back home

?feature=shared

On the way home first gear off ideal sounds ok every other gear it 4 strokes when getting back on the throttle

Jack here's the 122 MJ test

https://youtube.com/shorts/dSVe3NCNeHY?feature=shared

Here's a 120 video

https://youtube.com/shorts/CyeOdmKAFr0?feature=shared

And did a 118 even know you told me not to and still felt a slight splutter in there.

https://youtube.com/shorts/vE-B5eWReJQ?feature=shared

Which one goes the best?
The 118 sounds leaner but could be ok. Do a plug chop from wot. That will confirm if its still ok.

The 118 plug still looks rich to me, but I'm pretty new to this so I dunno for sure. The plug is newish (less than 25mi on it if I had to guess.

Yes appears rich. But was from a holding wot run on a fully hot engine? What number plug?

Yea, did the last WOT run with the 118 and checked the plug before I rode home. Didn't wanna ride home if it was whiter than my booty.
Fully hot yes. Temps at start were 200°F ish. Top temp was 293° with the sensor in the cyclinder head.
BR9ES plug.

Ahh, that explains it. Runs great but has a 9 plug. A correctly set up 9 plug will be almost dry black. Buy a 7 next time and you'll have some nice colour.

If the 120 jet feels nicer run that, otherwise keep the 118.

Alright I think I have a 7 plug. I know I have an 8.

Didn't have the correct plugs so had to order some. Got an 8 as well and am gonna try that one first just to be safe.

Will that change have any effect on jetting? I don't think it would but I'm no expert on the matter obviously.
Aka should I redo the main test with the new plug(s)?

None. Plug number affects the plug.

Thanks Jack

Good morning my friend, we are in exactly the same situation, I understand you, be patient and you will find the way out. When we say a turn on the mix screw, do you mean 180 degrees or 360?

Had a chance finally to get out and continue this journey. Had an 8 plug so used that.

Plug looks a bit better. Got a 7 plug yesterday so I should have some time tomorrow to give that a try.

Hello there, how is going? Do you finally found a decent setup without Decel popping and 4 stroking?

I 'm in the same boat with you for years now test and test with all jets available. The only setup that is close to what I want is with 45/120 idle jet 2 1/4 turns out ac 140 be5 128mj without filter but i think it runs a little lean.

Can you test this too and tell me what do you think...

I haven't touched the bike since June. I'm a stay at home dad and the kids start school again next week so I'll have more time then. I'll update when I get back to it.

ok man.