Modern Vespa

You certainly have an eye for making an awesome looking scooter. Fork looks shortened. Like the mudguard cuts on this, all goes together. I would put a screw in the mudguard even if the bracket isn't there anymore.

I have the Ginch exploding pressure plate in my 221. About 6 years at a guess. Loose but still working.

Want to start getting this thing jetted? You won't know what the power delivery is like until set up for fast road.
Pilot jet first. I have a new easy way for airscrews. Put the airscrew at 1.5 turns. Get the engine fully hot (short flat out run). Stop and let it idle. Surprise it at idle and open the throttle suddenly to full wot. If there is even the slightest delay to violently rev up the jet is too small. Up the pilot. Do another lap.

Not sure if you've mentioned this already, but the bottom brass bit below the needle (from memory referred to as the jet holder or needle jet - but stand to be corrected) has 8, 12 or 16 holes in it. I can't recall exactly what it does (!), but it certainly means that you can't simply translate genuine PWK settings to the Polini PWK.

108 - Your ride looks Mad. Good stuff, nice dark sleek look. Diggin the shortned fork. Gives it a bit more 'stance'. Thanks for sharing your build journey as well good and not so good. Your results are superb.

Wow, jack you noticed (a tear in the eye…) that is a sign of someone who's been around the PX a lot!

Yup, shortened LML front fork…

Yeah I previously had a bad PK/T5 mudguard on there thinking it was the T5 and realised it was too small, looked a little funny.

So managed to grab a 10quid bashed up mudguard, cut it with a grinder and painted it the same matt grey No worries, sharing is the name of the game… no idea what I'm doing most of the time tbh… lol

Thanks for the reed info. Might be a possibility one day.

I'm surprised you're running such a small carb on that build. I'm thinking a PWM *38* when I do my P200 reed build!

I have a Polini PWK 34 on my LML 187 because when I did the math, it said I needed a 32.8. With the bigger jug, I can't believe you're not in the same boat.

Now let's get some video, even if it's just on the stand

That stance looks really tough.

There's a calculation?? Worth looking into?

I'm not sure the 220cc can really maximise a larger carb, but I'm just guessing, also the new line exhaust seems a like pedestrian compared to other expansion exhausts…

One of the main reasons I went with the 28 setup was that I haven't managed to get the air bellow running on the airstriker… fuel economy was also pretty terrible… hence dropping down to the 28 and it seemed pretty balanced

I'm not a fan of using a pod filter now (even though I was running one for a good 4 years)… jetting it just isn't fun when it's full of fuel…

The Polini 28 will work, obviously. However, correct size for a Sport but it is on the small side if its an MHR kit. If a 60mm MHR then less bad. If a 57mm MHR with a 60mm crank, it needs to be minimum 30mm, ideally 34mm and if all out on a real high end exhaust 38mm.

Very rough, no complex calculation way to check the carb size is how big the main jet ends up being. Very approx half the carb diameter x10 is the ideal main jet size.
ie. 34mm carb running a 170 main jet is optimally sized.

How you get on with the pilot jet?

You're not far wrong about the fuel consumption. You only have to listen to the reed valve at full pelt to know that a lot of fuel is being sucked in!! I must admit I just bought the 35 AirStriker because it looked cool, but it actually turned out to be the right choice for my MHR 221. Had I raised the ED to 190+ and spent big on a PD pipe, it may have been a little on the small side

The calculation I use is:

carb diameter= K x (square root of (engine cc x (peak power rpm/1000)).
"K" for piston port engines is .9, and it's around .8 for reed valve engines.

And I agree that pod filters are not ideal. I like running with no filter for performance, but usually put the filter on for day-to-day riding as much to reduce the amount of gas and oil sprayed onto the motor as to maximize lifespan.

CM can you please put numbers in here to show how that works? Not very good with things in brackets. Or numbers if I'm honest!!!!

Sure!

For example...a reed valve 210 with a 57mm stroke, assuming nothing crazy, is going to produce peak power in the 6500-7000 RPM range.

so...

.8 * SQRT((210*6500/1000) = 29.5mm
@7500 RPM's peak power, it goes up to 31.7
Once you start putting a longer stroke crank on it and upping the cc's, the number goes up even further.

For a 228 (62mm stroke), I'm looking at a minimum of a 34 to even begin to keep up.

Thanks!

Because my math is so terrible, I asked google for help…

Copy and pasted the whole thing with a made up RPM of 7000

And it spewed out a graph, looks like I should be aiming for a 34mm carb

Quick question,
K is the lambda value?

K is just a constant to adjust for the difference in potential flow between the rotary, piston-ported, and reed.

Urgh…. Way over my head

When you thought some of the equation might make sense… lol

How'd you do that, exactly? I tried it and had no luck.

And, yes, I'd say 34mm is probably about right for your build. Maybe a little small, depending on where the peak power comes in.

Copy and pasted this

0.8 x (square root of (220 x (7000/1000))

I'm imagining the x value I need to multiply by 10 (cos that's the only way to get a number near the mm… lol)

You want this:

0.8 x (square root of ((220 x 7000)/1000)

Or, I guess It could simplify down to this:

0.8 X (square root of (220X7))

And simply use the RPM's in thousands

Giving an updated/simplified formula of:

K x (square root of (<cylinder>*<RPM's in thousands>))
K = .8 for reed
.9 for piston ported
and probably
.7 or .6 for rotary, depending on intake duration

That math makes a reed intake look better then rotary. I was doing rotary math at 0.65.

Had to make some changes on the side panel engine side. Cos it was rubbing on the flywheel cover, so in true Scooter and Service style, I made some changes… with a grinder (that's where I copied it from)

But of course a miscalculation, it rubs on the cover higher up now… lol (face palm)

First, your scooter is BadA$$; if I havn't mentioned that before. Did I miss somewhere you did a wide tire conversion? Why was the cowl rubbing on the flywheel cover?

+1 it looks great. I'm a sucker for dark grey with black accents. I'm also curious about the "great rubbing of parts". All sound very Life of Brian

I moved my MHR motor over to the right by 1.0cm in order to accommodate a 3.00 x 11" SIP rim, but the flywheel cover did not rub on the panel.

Thanks guys, just trying things out…

Trying to balance out what makes a PX, a street custom and ironing out those angles which are trying too hard in the 80's…

No there's no wide tire conversion… it's just a 100/80-10 on the back.

But I've always had a really tight gap between the engine (flywheel cover) and the side cover… the cover is cracked in 3 places, I've tried getting a welder to patch it up 3 times and it's gotten to the point where the middle has just flexed in… you can't really tell from the photos, but the steel has just pulled in… bashed it the last time I painted it, but couldn't quite get a balance between the shape and the pins fitting on the frame

So got sick of trying to ac/dc the existing wiring… I'm thinking it can't be done properly where the speedo gets enough power

So went a little extreme and gutted the wiring and installed a p200 dc loom with a battery… sigh… ended up being a ton of work…

Just catching up with this thread... beautiful work 108, you've got good eye and skills to match.

Thanks socal… I always say, if a chump like me can try, anyone can do it!

looking good.
I have always found the P front mudguard a strange fit - to my eye.
Sacrilege I know - but since you've made a street racer out of yours - the changes are a nice match.
Looking good all around.
-CM

Thanks CM2!

Yeah exactly, there's something "off" with the stock mudguard… the proportions are a little odd looking

Trying to put my finger on it.

Unfortunately this is far from stock now… not everyone's cup of tea for sure, a bit sacrilegious, but hey, was a beaten up bike when I got it…

Need to get some riding video, still trying to figure out how to strap it down without the phone flying away

Do you have any pics of what you did with the fork when you shortened it?

Hey GT,

I brought the fork from scooter and service back in 2015, it's the last lml modified fork Wolle made before only using piaggio forks now. It was a bit of a steal so was lucky on that front.

But here's some images stolen from the inter webs I saved if I ever needed to do it again…

After I got my Sprint, the Stella/P mudguard started to look really W I D E to me, especially with the squared lines.

And be careful with your phone. I had mine in a mount and had covered many miles that way, but a solid bump at highway speeds was all it took to send it flying.

Yeah wide and a little clumsy looking, right?

I'm trying to bring back a more "rally" style to the mudguard… hopefully narrowing the stock mudguard by 20mm will give it a slimmer profile.

But not sure if I'll like it, hence trying 2 mudguards at the same time… atleast I won't need to take the handlebars off twice if the mod doesn't work… which I have a feeling it might not fit!

Yeah apprehensive about the phone on the handlebars, given it's a gift from the wife… lol

I just went and measured all my bikes' fenders. The Stella is the widest by far. The Sprint is effectively the narrowest since it has a 10" wheel.

My GL fender looks like it's bowed out a little in the middle, but that's because it's had a hard life, not because it came from the factory that way.

This is pretty awesome to see the comparison

How different are the forks? The part that will be a deal breaker is the distance from the head tube (center of the bike) to the shock (horizontal).

Poor GL…

Lemme see what I can do to measure that. Won't be until this evening, though. Gotta actually do some work for the rest of the day!

And I'll smoosh the GL's mudguard back into shape at some point, but I feel like every time I do, I almost immediately trip and fall onto it, knocking it pear-shaped again.

No worries…

Would be cool to compare…

But too far down the line of fibre glass and cutting the mudguard now!! Lol

Managed to score a front fork, hub and mudguard… so will measure and see if there's any fitment issues

Doh! I spaced on this. It's been kind've a crazy week at work and it slipped my mind.

I guess I'll just sit back and wait to see the results

Not looking forward to pulling out the paint gun…

Definitely not in paint shop mode