Modern Vespa

My jetting is the same as that post but now BE4 and 122 and have to go up again on main to see if it bogs. If it doesn't bog again it could be the restriction in the bowl acting as a jet.

Yeah it could be acting as a built in jet. I'll look into it. Thanks

Drilled the bowl passage. Practiced on the 1963 20/15 which was like 1 mm. Talk about bottle neck. The modern-ish 20/20 passage was negligibly bigger. Was only semi serious about the passage acting like it's own jet but I believe it now.

After drilling it actually seemed like it was borderline rich. Possibly a placebo effect but will find out tomorrow. Late now.

ETA: Dipping the drill bit in grease will help keep the chips from getting everywhere. As you drill clean the swarf off periodically. Once finished there will be MUCH less of it to worry about. Process is generally used when something can't be disassembled for cleaning after drilling. Obviously still clean it out but there's less chance of any errant bits being missed.

Good call!

After drilling out and test riding back to work after lunch it WAS noticeably richer. Had a hunch it was when idling after drilling, but wanted to see how the test ride went.

That explains the up and up and up on the Main. It's only slightly boggy so one jet down to 120 should do it but we'll see.

If that works out I need to dial in the 1/4 throttle area. Idle great, 1/4 throttle not, above 1/4 throttle great.

One thing at a time tho!

Hmm. Welp! I spoke too soon. On the way home it no longer bogged but was still flat. Guess the 122 needed more time to percolate.

Popped a 125 in and it FINALLY pulled somewhat at WOT. It also ran better in the 1/4 throttle area. I was starting to have an existential crisis. 😅

Going to go up another Main but I have a feeling it will run better yet again. Makes me wonder about all the kits running on a 108 Main or did I get some kind of prototype parts? 😀

Air corrector and carb size impact the main size a lot

You'd think everyone with a Pinasco 177 and 20/20 would have the same ballpark jetting. They're a dime a dozen from what I've read. The consensus jetting for that basic vanilla set up was 55/160, 160, BE3, and 108. I'm now at 50/160, 160, BE4 (4 steps richer than BE3) and 125 and it wants more. It didn't like 140 Air.

I know every motor requires a different tune but still. It's at 125+ because it wants it. Odd that the exact same build wants 108.

It is what it is. I'm just trying to get mine dialed it. I have a lot of experience with motorcycle carbs (singles, duals, inline fours etc) so this is new and interesting to me.

Quality and accuracy of jets sizes vary.

Oh, I bet!

I'm with you Gomo.

I've been running mine for a few years now and to keep temps under 300 at WOT I had to got a lot bigger than others seem to need to go. Then again I ride WOT for miles.

And my experience has been that the kit runs hot on account of the internal third port. My 2 cents anyway...

Now that I give it a bit more thought, I do have a nice Pinasco crank installed, and I opened up the intake on the rotary about 8 degrees, so it'll handle more fuel/air....

Oh wow! That's all very interesting. The whole two stroke puzzle is really intriguing.

Yeah those specs are off the chart. Do you have trouble using both wheels? 😄 I imagine the front likes to come up if you're using that much juice. 😅

From my limited 2T knowledge those mains, mixers and correctors represent quite a good fuel flow. Matches up with what you said about temps. I see that with air cooled 4T bikes. The fuel is actually part of the cooling but to a lesser extent.

Qascooter has brought in more variables - did you open up your intake? Cut crank? Which pipe? All of those go into the varying answers. Reed valve Stella vs rotary? So many flavors. But he's rolling a 24.24 - and the main goes quite a bit bigger between the 20.20 and the 24.24, even if nothing else moves.

Yeah I understand that. I'm not new to carbs. Like I mentioned previously I have a lot of experience tuning carbs on performance 4T motorcycles. I've also tuned fuel injection on forced induction automotive applications. I'm just new to this carb, platform and 2T in general. It's a curiosity to me and I find it interesting.

This is a build thread so may just have to scroll back some to see what's done. Sorry for not reposting it. Gets tedious.

I appreciate your knowledge on these though. I've seen and benefited from your input on other posts during my research.

No worries, I was just pointing out all the flavors. You're going to jet it by experiment anyway, we can see that already.

Oh definitely. Your insights I've read were very helpful. Thanks!

Yeah hopefully it doesn't blow up in my face!

I think this thing is giving me a two stroke affliction. I've been catching myself eyeballing different two stroke scooters and bikes in the classifieds.

RD 400

Oh yeah! Pinnacle late air cooled? I've seen a couple RD400 Daytonas for sale. One was even a fixer upper.

I'm not sure I want that level of niche trying to fix up one of them. Can imagine the scouring trying to source things for reasonable prices. Unique is great until it's an old vehicle you're restoring. I was shocked by how much was needed to get an old 125cc 2T scooter up and running and that has part availability out the ass.

vespas are a cheap hobby compared to where it can go

old car stuff adds up fast, lambrettas add up fast, etc. etc.

Yeah but I've found it A LOT cheaper and easier to get a basket case 4T motorcycle up and running. Like exponentially, but I guess this scooter may have just been an extreme outlier. Most people probably try to start with scooters that just need a tune up rather than a nut and bolt down to the frame mechanical restoration.

Totally agree. A nut and bolt restoration really adds up, especially all the little bits. But it's doable, even on a budget. 2t's tend to be a lot older than 4t's. So many little things that crumble or that you wouldn't want to reuse when you take a 2t to bits.

Yeah true. The differentiating point is when you don't have a choice of whether you're doing a nut and bolt or not. If I chose to nitty gritty it, then so be it. This one chose for me. Everything was basically shot. I had to do a nut and bolt just to get it to safely run again. The optional performance and handling mods I did were just so I wouldn't get run over and quality of life, which are the same thing I guess.

Biggest lie ever mentioned here

Speechless

i see what you did there with the selective quoting

Wasn't available to work on it this weekend so did a bunch of research instead. Seems to be a lot of people that advocate for AC140 if there's even moderate uogrades. Typically paired with a BE5. There's different theories on the why part.

Anyway, finally got home and decided to try an AC140 and BE5. Remember when I mentioned my scoot didn't like AC140? It still doesn't. With AC140, BE5, MJ125 and a 55/160 it bogged down, flooded and fouled the plug by the end of my driveway.

Pushed scoot back into garage and reverted back to original course of action. Swapped back what was originally in there plus upped the MJ in pursuit of the BOG° and installed an AC160, BE4, MJ128 & 55/160. I believe I've finally found the BOG° with the MJ128 so MJ125 is my clean one.

Next I want to work on the idle and quarter throttle. First I'm going to try just changing BE5 since it has less fuel at idle and see what that does. If no improvement I'll lock in BE4 and then experiment with the idle jet.

Pinasco at least recommends the AC160. I also tried the 140 on mine and it was not happy at all. Now it won't start at all and I haven't had the time to look into it yet.

That's interesting about Pinasco and your experience as well. Mine wouldn't start again either. Plug was fuel fouled. Wire brush and brake cleaner and was able to get started again after changing back to AC160.

you probably already know this but when you drop that AC from 160 to 140, you're gonna end up like 10 points lower on main jet or something. i'm not sure if there's a good rule of thumb but it's significant.

I ended up in the middle for now.

Went back to where I was plus one up on main, AC160, BE4, MJ125>MJ128, & 55/160. MJ128 was dirty so MJ130 was probably the hard bog point.

But... I found a chart with mixer breakdowns and it showed BE5 being the same as BE4 but leaner at idle so I went with BE5.

So now I'm at AC160, BE5, MJ125 & 50/160 with A/F screw 1.5 turns out and idle screw 2.5 turns out. Idle revs out really cleanly now. Dark and late now though so will test ride tomorrow. On paper MID and WOT should be dialed in. 🤞

Yeah I've read about that but not the scale you mention. I assumed MID and WOT would be affected. Idle has its own circuit. I know there is some MJ overlap with the Idle Jet but wouldn't consider it enough to fuel foul the plug that quickly. I made it to the end of my driveway and had to push it back.

I think, in my humble opinion, that the AC is a nexus of tuning theories. End of the day you get the same A/F ratio. You are just lowering the jet sizes you use. Probably better gas mileage with AC140 and I would guess better temps with AC160 since more fuel is needed to reach same A/F ratio. 🧐🤓🤷‍♂️

I'll see how it goes tomorrow.

This may be sacrilegious but it's technically correct and that's the best kind of correct. 😅

Also it's got a place for one right there!

Added an 8mm mirror bracket from SIP and a Brake Free helmet mounted wireless brake light.

The mirror bracket cause it's weird not being able to watch my back. Coming from motorcycles, which are much less vulnerable, I've gotten used to them. I'd argue they're needed even more on scooters.

Same reasoning for the Brake Free light. This scooter's brake light is dismal and dim and about a foot off the ground. Multiple reasons why no one will notice it. An added plus is night time visibility. Worth looking into. I found this one second hand on ebay.

For an AllState??? Ah hell no, it's perfectly appropriate. Made by, not some crap made by Bajaj or LML!

True! Awesome!

I have to ride with a mirror. Just one. Had 2, but took off the one on the right to mount a phone. I could never see anything out of it no matter how it was adjusted. You can't go wrong with safety upgrades. No one on cell phones when Allstate's were new.

Interesting idea about the phone mount! Yeah I just got some basic early Honda style mirrors. Will be here in a couple days. See how it goes. Trying to find a happy medium where I can see behind me but they're not three feet long.

Well, I'm a convert to the AC140 theory. Finally had it's beneficial fluid dynamics explained a little more precisely.

In all my research it's only been very vaguely explained. Mainly less air equals more fuel but on the surface that is contrary to what the uninitiated sees. Yes less air but your jets also go down so less fuel. So on and so forth.

As explained to me: "The AC controls the air supply to the vacuum in the atomizer. Less air, more vacuum, much more fuel, smaller main jet"

As I understand it, the smaller AC pulls the fuel thru the main jet circuit quicker and with more volume. This also aligns with the only other example I've seen where another member compared it to straws in a T formation. With the bottom of the T in fuel and say the top right T providing vacuum. If the open end of the T is too big you lose a lot of vacuum thus get an equally inadequate amount of fuel. Reduce the size of the open end of the T and you increase the amount of vacuum and also the amount of fuel.

Anyway, I went to an AC140 and popped in a MJ115. Idle seemed lean so went with only richer jet I had which was 55/160. So at that point I had AC140, BE5, MJ115 & 55/160 installed.

Ran well and a nice improvement overall and didn't bog. It ran better when I pulled the choke out at WOT so it wanted more fuel. Bumped up to a MJ118 and there was again a noticeable improvement overall. There was still no bog but it also didn't bog or improve with choke at WOT either.

From my experience tuning 4T motorcycle carbs, generally if it pulls good and then stumbles with choke at WOT you're as high as you can go and done. If nothing happens when you pull the choke at WOT it's up for personal discretion. It doesn't need it since it doesn't pull better but it also isn't at it's limit since it didn't bog. Basically go up a main jet and see what happens. This is where a half jet could come in handy and be interesting. I digress!

I'll try a 120 next just to find the bog but I think 118 is it. Also found it pulled better in 3rd vs 2nd. My lizard brain thinks it wants a tad more fuel though since it pulls slightly better in 3rd vs 2nd with the 118. Will find out soon. Rain forecast after work so may have to wait a while.

Main locked in at 118. Flat spot between idle and mid. Richest idle jet I have is 55/160. Ordered 50/120 and 52/140 to test.

While I'm waiting I swapped in BE4 due to its extra fuel at idle while being the same as BE5 elsewhere. Would at least validate or invalidate the need for more fuel between idle and midrange.

Current: AC140, BE4, MJ118, 55/160

It was a definite improvement and actually runs well before mid and really well after mid now. It's surprisingly zippy and midrange really pulls for what it is.

This build is definitely more of a torquey midrange type deal. Still goes at WOT but the strongest acceleration is between 1/4 and 3/4. Great for zipping around town. I never intended to use it on higher speed roads.

I do plan on piecing together a bat shit motor in the future. Keep it on 8s as well.

Another thing I want to try is a 10 only on the rear. Only raises it an inch so better ground clearance and higher top speed at least on paper. Not anything urgent though.

Will mess with the other idle jets when they come in.

Overall impression so far on first vintage shifty smoker is they are LOTS of fun! My AllState is apparently a pretty basic one too! I like it tho!

Most excellent. 8s are super fun to zip around on. Good job dialing it in [/url]