Modern Vespa

So, for a start, and to be clear, I haven't started to make it go faster yet.


What I wanted was something that was fast out of the box. Once I have run it for a year or two, then I'll probably want to upgrade the carb and pipe, maybe lift the exhaust? But all that is open to me at the moment. Aside from the Uncle Tom crank it's 'stock' Quattrini. And I wanted the Uncle Tom because it's not full circle like the Quattrini crank.

If I'd started with an MHR and built a bit-over-30-hp motor from it, the mucking around, big carb, expensive pipe would have been much less straightforward and probably not all that different in cost. Then, in a year or two down the track, where do I go then?

Super useful! Thanks for the links.

Yeah I think it's safe to say it's a Polini pwk 30 in the tests.

Same one I'll be using on the build I'm working on.

The jetting they're using was the jetting I was hoping to use too. That's interesting, I wasn't far off in my guess. I would've used a larger main jet.


Polini pwk 30

45 pilot, jjh needle, 145 main

Pwk 30, Italkast reeds

I didn't think to look on the dyno! I only noticed this, but looks like they only used the PWK in their tests - I had expected to end up around the 150-ish mark, a couple of local guys said that was about what they were using from memory.

What's your plan for port timing? And which crank?

Yeah shame they seemed to have given up on the phbh. Would've been interesting to see. But I don't think it will deviate far from a 210 build. I'd be surprised if the main jet hits 150. But hey, never tried the phbh on the 244 (252 in your case) myself, so you never know.

Well, the 244 started life with a rotary valve. So will be reusing the same 62mm crank in the Reed build, won't be buying a new Reed crank for this. The exhaust is a sip box 3 so will be aiming for the mid-180's for the exhaust port and the transfers to match. If it was up to me, I'd probably would've gone for the Polini box.

Aim here is to have a ridable Vespa. The previous rotary setup wasn't even ridable.

This one's not yours? Why was it not rideable?

Not mine.

A project I'm helping someone with. Was built by someone else.

Before I had seen the bike, seized a few times already. Bike started though. Had a fuel pump on a tmx carb on a rotary. The jetting was all over the place. I think it had a 150cc exhaust on it previous to the sip 3.0.

Before I split the cases I did a pressure test, the crankcase leaked like crazy. Fuel in the gearbox oil. It had a leak in the cylinder head, nicasil coating had come off in a bunch of places. Looks like a bunch of heat seizes and the bottom piston ring got spun around (away from its locating pin) and got stuck. It's amazing the bike started.

To be honest the crank isn't perfectly straight no more, the seizes probably the cause, but it's acceptable to reuse.

You clearly enjoy a challenge!!!

Usually enjoy it more when it's your own bike. Lol

Rebuilt 5 engines in the past 12months. Unfortunately none of them mine.

Rebuilt my egig 170 twice. That was fun. Well, riding it is fun.

That sounds... unfortunate! Except for the riding. Have you compared it to an M200?

I've only ridden a terribly put together Polini 112cc, the egig 170 and a stock et3 smallframe. So I don't have much to compare to.

Of course I had the malossi 221 that I was tuning for 8 years.

Something tells me the m200 is a bit fast. But I did do some calculations, costs a hefty chunk of coin. I'd rather be buying disc brakes.

A mate built one and I was lucky enough to have a ride. Yes it's fast but not an uncontrollable explosion... although he does say you have to watch it putting down power coming out of a corner!

What you have built is great. Going to cruise really well and have plenty of torque. It will do 75mph , maybe even 80mph. Will be a lot of fun to ride for many years.
With the 62mm stroke and very long rod there is a much lower rpm ceiling. So any future tuning needs care.

Concerned your mix screw is in too far. Typically on a 55 pilot, even with an AS268 it ends up over 2 turns. Any sound recording while adjusting?

Good to know. I realise it's on the dyno so not real world but I saw in the SCK 252 series that the Polini box peaked out at 10k-ish. I guess you're saying that it's unlikely to last long at those revs?
Anyway I prefer torque over high revs so should be good.

No I haven't thought to record idle adjustment, I'll do that tomorrow if I get a few minutes free.

The extra jets turned up today so I took it out on a test run. I had the X32 on second clip, the AS264, dropped the pilot to a 50 and started with a 180 main.
High idle was still around 1.5 turns out. Drop it further again?

It felt good, not quite as smooth a cruise as I'd hoped (tried the needle back on the first clip but only made a small improvement). But anyway, even without pushing it it pulls like a train. Hard to hold back!

The 180 flooded at 3/4 (probably, it was dark) 170 better, 165 I didn't hit a flood point but was back in the suburbs by then. I'll order a 168 and see how that goes.

We have progress. Get the main jet good before worrying too much about the clip. Be absolutely cock sure the main jet is not lean. When deciding about a main jet, up it ten points and it will be un-rideable rich, if it was correct.

Must have the pilot mix screw at 2.5 turns when temporarily at a high idle (1500rpm). Then reduce idle screw to slow idle (800rpm) with a solid thudding beat. Rev up immediately from 800. Start hot easily.

35bhp will feel like a handful, so thats a sure sign it's going well.

Changing the pilot to a leaner one (so as to be able to achieve the highest idle at 2 1/2 turns out) has made the cruise bit much more jerky. Perhaps I'm going in the wrong direction and the pilot needs to be richer?

Didn't get a chance to record the sound last night, I just changed the pilot to a 46 and rode it to work this morning. No main jet testing in this traffic!

46 is not usual on a PHBH. 60 is more the norm. Need to hear how you're adjusting it.

Tried a 58 pilot (don't have a 60). In the video where it starts to speed up - that's the mix screw adjusted all the way in after a starting point of 2 1/2 turns out.

https://youtu.be/JcH_39BHXXc

And here's some audio cruising at around 60 kmh

https://youtu.be/AOJO95250ac

Idle is not fast enough for adjusting. Can see the lights flickering.
Idle screw all the way in then out 1 turn, if no rev counter.

Start with mix over 4 turns out, smoke and a splutter as the throttle cracks open. Then adjust out the splutter.

Riding around sounds boggy between shifts. Not sure if you're easing into the shift or it's just rich at low throttle opening.

Can't tell not seeing the video.

With the 58, Does it stall at lights after riding 10kms or more?

At least it's up and running. Doesn't sound the most fun though.

So I tried all of those things and came back to the X13 for comparison. It took out all of that jerkiness that I thought was the pilot. Also went back to the 55 pilot. I can't get any of the pilots to run at their fastest at 2.5 turns out, settled on 1.5 turns out. I swapped to AV264 and it felt similar to the AS264, if someone else had done it I wouldn't have been able to tell the difference. Also tried AS266, definitely a bit richer and not really as smooth but quite rideable if not as pleasant.
Also worked down from 180 main in 5 point increments. The first one that would not start to gurgle at 3/4 to wot settings was a 145.
I also swapped the X32 back in to double check my thoughts, I think on a proper pipe it would be fine but perhaps not on the Polini box.

On a day with a howling headwind up a big hill I could do 90 - 100 easily and temps were in the low 300's. I did the same 20km loop three times (or was it 4? Had to go back and find my glasses!) to test. And very happy with those results.

Now on -
X13 needle
55 pilot 1.5 turns
AS 264
145 main

I have a couple of people I know who are also using a 244 with PHBH30 and they both independently ended up on X13 and 55/53 pilot. The 260 used an AV268 and 138 main, the 244 used AS266 and 150 main (although he said that was still a bit rich). That makes sense now. Bit of both really. My gear tube is very worn so it's hard to adjust the cables nicely. Easy to miss a gear if I'm not careful. I have some PK polypropylene shims that I'll try when I get a chance.

Sounds like this could work, and about right.

Have you tried

X2needle and AS266?

That's what I would've tried use. 142-148 is what I'd expect. Like I mentioned before, I'll be surprised if the main is over 150.

The X13 and smaller 264 should be similar to 264 and x13, but the x2 and 266 should have better fuel flow.

No I haven't. I'll give that a go... not sure when but it\s all worth a shot.

Interesting side note. My friend Stefano from Italy (Sardinia actually) has mentioned a few times that he finds the jetting here in Aus. so much leaner than at home, and can't work that out.

Yeah, give it a go, it's be my choice, but like you said you could be a little more on the lean side. You've covered a lot of bases.

Doesn't surprise me that. Weather and humidity have a huge effect on jetting. But it's usually within 10points.

Weather for me is hot and humid, so it's also leaner. Which is kinda scary because you want to run rich to cool things down. But actually I found running rich is bad, because your needle, idle jet will be lean for you to be able to start the bike. That's when the overheating and seizing can happen too. Not just at WOT… When you're going 60mph and the throttle is 1/4 open (plus 30c weather), that's when things can get interesting real quick.

Definately jetted leaner than I thought. Might be leaner in Aus. With the temp going over 300f too easily I am concerned that it might actually be lean.
With the main jet at 145, it could take a smaller atomiser. Seen people run AS262 before.

Actually that's a point…

You can just try the x2 needle first without the atomiser swap. If there's an improvement, you can change to a 266.

If it doesn't help, easy to go back to the x13

Saves you doing it twice.

I'm thinking that yes, it's a 252, but the port timings are fairly tame especially compared say, to your 221. And the Polini box still has it's original (19mm?) outlet. The friend with the 260 has built 3 of the Quattrini's for himself and a few for others... so I feel like his jetting is not wacky.

Is a 262 leaner than a 264? I've been assuming that it is. Yeah I'll definitely give it a try at my next session. Cheers.

Did someone say leaner?
I don't even see a side car.

Is this a tequila inspired insight?

Yes! On February 20, 2019. https://modernvespa.com/forum/post2304312#2304312

Yes, AS262 is more lean (leaner; nothing to do with the perpendicular). This might make the mid throttle too lean but worth a try to get the pilot jet at 2.5 and main jet slightly bigger.
What float weight is in there?
With the mix screw adjustment. If the idle speed is the same as it was, at the end of the 20km run. Hot re starting easily. Has power at 1/8 throttle and will hold a flat cruise there. Then the jet and atomiser are not so bad.

For the other three readers, who think 2 stroke cubic capacity is everything. My 221 runs clean at wot with a 195 main jet. And a 270 atomiser. It has the most port timing that works on the road (in my opinion).
If you ever decide to tune the 252 (and buy loads of expensive bits) to similar port timing/angles, it could be ridiculous.

Float is whatever came with the carb. Is there a marking or do you have to weigh it?
Locally they're out of the AS262 but I will need to place an order in the coming weeks, need new o rings for the Pinasco rims. Hot starting is definitely no issue. Certainly has power at 1/8 and will pull from there easily. But at a steady cruise let's say at 50kmh in 4th it's not smooth as such. Though not jerky like the X32. Yes they're certainly different motors, and as you suggest port timing is the Jekyll and Hyde factor. At this time, I think I'll be very happy with the effortless way you can exceed the speed limit, and hope to do a nice bit of touring in the coming year. But eventually you get that itch...

Ah that's a good point, float that came with it will probably be fine, 9g if I remember right.

But the float valve will definitely need an upgrade. Not sure if you've installed at the moment.

Didn't affect my jetting, but did affect sustained wot runs.

Below is stock 200 vs 300 valve size.

I was recommended the 300, but I figured as I run a fuel pump it's not so important?
I did try to find something on the float that identified it by couldn't see anything.

Ah you have to take it out and there's a small number. But you can also tell from the float needle, much smaller and a different shape (the 250 is the same shape as a 200 if I remember correctly)

Yeah with the 300, no fuel pump needed.

Checked with a clear float bowl which is large enough and with the fuel banjo angle adjusted to your liking, no starvation issues.

Saves installing a fuel pump.

But yeah, won't need to swap out if you run a fuel pump

I tried the X2/AS264 this morning, quite rich down low but ok in the mid range. So thinking I'll stick with the X13 for now.

Righteo, using the x13 sounds good mate.

Great it's in a good place!

This not smooth at 30mph is an issue. Where is the throttle at this cruise? I would hope 1/8. The X32 would be much richer than the X13 at this point but still wouldn't rule out a too lean issue. With the pilot jet at 1.5 turns, this might be the problem. How is the CHT if you hold this speed for a while?

Yes 1/8 would be about right. When I've held it there for a while, the temperature typically has been sitting I'd say in the 250-ish range? But I haven't specifically tested for that. How far/long is enough to give a good indication?

This morning I had left the mix at 2.5 turns and had to bump up the idle speed so it wasn't in danger of cutting out at lights. Seemed to run well enough like that.

Did the 1/8 cruise smoothness change with the 2.5 turns?
Holding steady under 250f for 5 minutes or more, would suggest it's in the ballpark.
At the end of the cruise, opening the throttle 1mm more it should pull hard immediately, when everything is set correctly.