Modern Vespa

Ugh. I guess is going to get complicated after all.

Easy peasy, you can knock that out. Going to pull my jug and tune my exhaust port too before I run it.

I don't understand the where/how/why of welding the crank pin.

You can definitely just stick the cylinder on and aim for 1.3mm squish. But it's free power to be honest with the port width and adjusting the port timings. Even if you're building a tourer, it's worth doing.

And it's not going to do wheelies, or be a power monster, gearing will do that part. Just adjust the gearing characteristics to how you want to ride.

I thought mazzus were welded now…

I do them like this, never had an issue. MMW was doing laser welding for SIP / Serie Pro cranks, don't know if there's a welded Mazzy…

😆 I ment tuning up the exhaust port. If you don't have a tig I would definitely have someone weld the crank pin for you.

I am TIG-less. But I do know a guy. He welded up an absolute door stop of a 2 port case for me. Being a 2 port case, it's still kind of a door stop.


The crank pin looks fairly straightforward.

Exhaust port. Maybe. I will measure the timings and see what I get.

Ignition. Do I really need variable ignition? I have a new PX stator in the bike that I set up for full DC. After a lot of fussing and wiring repairs, it makes everything go. Battery was still charged after sitting all winter. And that's on a Stella.

Still mulling over this crank and questioning if it's the best choice. Makes me realize again that you can't just throw off the shelf parts together and expect it all to work out.

Going to a reed valve brings up a number of considerations with the shape of the crank, namely reducing the volume the crank webs take up to make room for fuel or changing the shape to allow fuel to flow through. There is also the position of the crank which affects how much it restricts fuel flow.

I'm guessing that these changes vs a rotary crank have the potential to reduce the strength of the crank and make it more prone to twisting, as does increasing the stroke. And there we have the age old balancing act with performance vs reliability that crops up with every engine in the quest for power. And then we get to the solutions for the problems that result. Reading up more on welding the crank pin, it seems that it's somewhat controversial.

The crank I bought clearly doesn't have the pin welded. The only downsides I came across in looking at this solution was the potential to warp the crank when welding and that it makes the crank harder to separate down the road. I don't think these are big considerations with this crank and welding the pin is low cost insurance. A couple TIG spotwelds is not gonna warp the crank.

I'm hoping that the low level of tune I'm aiming for and my sedate riding style will make twisting the crank unlikely. In retrospect, I might have gone with a Malossi rotary case and chosen parts closer to stock. Probably overthinking this, but I like to have a basic understanding of what I'm putting together.

Thoughts?

Don't know much about crank styles for for reeds but I would definitely weld that crank. SaFiS has tons of experience with all the scoots he has and works on to not take him up on that recommendation. I read lots of reports of the Mazzy cranks wandering in my research. You already have the crank so might as well use it. Like you said, not pulling wheelies or hauling a trailer with it.

I was on the fence about which cases I wanted too. Even though the SI style carb is an odd design for me, I picked the rotary case to keep it simple and more stock like. Definitely want a robust touring engine and something on the smoother running side. Hope the SIP crank I got gets it done. Was just going for a more plug and play gig like FMP did but from the reports I've heard Jack and 108 talk about, makes sense to get that exhaust port tuned better. I should have mapped my cylinder anyway. I was just being a lazy bastard. Haven't run mine yet so I'll pop it off and get it done.

First one of those cranks I've seen with SIP stamped on it. Got to be at least grade B now. The cranks only twist when they are part of a significant overheat. Don't overheat it, no problem.
Once its welded that's it. Very difficult to change the conrod in the future.

Which definitely is the downside to a welded crank

Right. There are always downsides and no guarantees. It's just expensive enough for a crank to not be disposable. But whatcha gonna do? If it pops, it pops.

I have the same crank, has the SIP logo on it, I measured if it ran true straight out of the box, was pretty straight, not perfect, gauge needles moved but not enough to register a reading.

Installed it, ran it, but preferred a full circle crank for responsiveness off the line, I'm guessing inertia and crankcase pressure probably being a factor. Just me being anal, especially when i had to crack open the cases to change the gearbox at the time.

I've never welded a crank, if it comes already welded, thats great, added bonus. but if the crank twists its usually something thats happened, like a seize... I just run them as is and worry about longevity later... the worst case scenario is a crank swap, which on a p largeframe, I'm more than happy to do.

Should be ordering the remaining parts for this engine next week.

I am trying to figure out which additional jets to order for the Dellorto PHBH 30, as in the dimensions of the pilot and main jets. Are they the same?

According to the Dellorto parts diagram, the part number for the main jet is 6413 (6mm) and 1486 (5mm) for the pilot. It's confusing.

Thanks.

Yup, 5mm for the pilot, 6mm for the main.

48-60 pilot 120-155 main will cover you for experimentation, from 177-244cc.

Also a bunch of needles and atomisers. x7, x2, x13, x25 and AS262-268 should have you covered

Thanks! That's exactly what I needed to know.

This is a pretty good way to buy the needles.

https://www.scooter-center.com/en/needle-set-bgm-pro-dellorto-phbh-x2-x3-x4-x5-x7-x13-x25-x32-x44-x61-7671253?number=7671253

Thanks Ginch,

Always good to have those little brass bits before first start up. Waiting for them can be tedious.

Another couple questions came up. For the clutch cog. Just double checking that I have the right one. I will be using a P200 65t primary on an EFL Xmas tree. I was thinking of sticking with a 23t clutch cog, at least to start with. Will this cog fit?

https://www.sip-scootershop.com/en/product/clutch-gear-cog-23-teeth-drt-clutch-cosa-2-drt-primary-z-65-z-67-z-68_87475000

I'm also wondering if it would be possible to use the stock 7 spring clutch, at least to get started. I know this engine will be more powerful than a stock 200, but it's not going to turn me into a faster or more aggressive rider, at least not right away.

Last question. On the SIP site it states that the Malossi sport version of the cylinder kit will only work with a 57mm crank and the MHR version is required for 60mm or longer. This doesn't make sense. Pretty sure SIP is the only place I've seen it in print.

Thanks for answering my endless questions.

No. But this one will
https://www.sip-scootershop.com/en/product/clutch-gear-cog-23-teeth-drt-clutch-cosa-2-primary-65-teeth_87476100

7 spring will be fine for a while. Stiff to pull and jumpy but if it doesn't slip, it will do for now. As long as you have a P200 23 tooth cog with it.

Thank you. Really glad I asked.

Definitely.
Make sure you get a selection of base and head packers at the same time so you can play around with port timing to some degree (see what I did there? )

Pretty sure I had to take a small amount off the bottom of the piston to clear at the bottom of the stroke, other than that it was pretty straightforward from memory. I think that I had read somewhere that they changed the piston design in later versions to avoid this.

Yes, those too. The nice thing about the Malossi stuff is that you can find consumables for them in the states. Also helps that the design is proven and has been around for awhile.

It looks like the Dellorto PHBH 30 is out of stock at SIP.

Would the SIP version be ok or should I try to find the genuine article?

Thanks.

https://www.sip-scootershop.com/en/product/carburettor-sip-dsrc-30-bs-03343-round-slider_40033000

I bought one but haven't used it yet. It certainly looks good, nice quality casting. Came with an additional slide!

Thanks. Looks like there are a number of versions of the Dellorto PHBH that SIP sells. The difference seems to be the jets, slider, needle they come with. It's confusing if you're not familiar with them.

There are also other differences with PHxxxx carbs, like idle & air screws being left or right, positioning of the fuel line, choke lever or choke cable, line for oil injection, etc.

Still lost sifting through all the variants of the Dellorto PHBH 30. Can someone point me to the exact one I need?

Many thanks!

Phbh 30 BS

(NOT BD)

So, idle screw and fuel mix screw is on the left (because we install the carb backwards, the screws are on the right of the Vespa)

Definitely get the idle and mix screws on the flywheel side.

Yes. This one
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/complete-carburettors-dellorto-motorcycle-carburettors-parts/phbh-26-to-30mm/r3343-phbh30bs-2-stroke/

This sip one has a cable choke fitting already
https://www.sip-scootershop.com/en/product/carburettor-dell-orto-phbh-30-bs-03478-round-slider_D3478

Never used one but this sip own one looks like its worth a go
https://www.sip-scootershop.com/en/product/carburettor-sip-dsrc-30-bs-03343-round-slider_40033000
cheap, for sure. Cheap rubbish who knows.

Probably not that one… it's got an oil feeder… (hence the expensive price…)

You want to go for the plain 30BS

This one:
https://www.sip-scootershop.com/en/product/carburettor-dell-orto-phbh-30-bs-03343-round-slider_40030000

It's stopped showing up in their search engine, probably because they want you to buy their SIP version…

I remember the dellorto was around $100usd before… prices have gone up…

This is the oil feed one
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/complete-carburettors-dellorto-motorcycle-carburettors-parts/phbh-26-to-30mm/r3478-phbh-30bs-with-oil-feed/
Why is it cheaper (less expensive)?

Have you used the sip own one? I don't know anyone who has.

Thanks!

This one:

https://www.sip-scootershop.com/en/product/carburettor-dell-orto-phbh-30-bs-03343-round-slider_40030000

…is the one I wanted to go with, but it has been out of stock for awhile.

This one:

https://www.sip-scootershop.com/en/product/carburettor-dell-orto-phbh-30-bs-03478-round-slider_D3478

…seems like the same thing but with different jets and air corrector. Since I'm buying an assortment of brass bits anyway, I guess it doesn't matter. It's also in stock.

As for the SIP item; could be a diamond, could be a turd. Since they like to stamp their name on everything, it's impossible to know.

There is also this one at Scooter West:
https://www.scooterwest.com/malossi-dellorto-carburetor-phbh-30mm.html

So is that an auto lube carb? I didn't know such a thing existed.

No… the one Jack mentioned has this oil feed… (see below image)

It's not the one you would want. I've tried the one with an oil feed and swapped out all the jets, doesn't work… I think there's a few passages which are different which affects jetting… problems at idle… would just bog down.

I honestly thought it would work too, but doesn't… lol

On motorbikes the 2 stroke pump has a pipe in and pipe out much like a fuel pump

Thank you 108! You helped me dodge a bullet. Carbs are enough trouble even when you buy the right one. I did well to ask.

10-4 Jack. Autolube side draft for Vespa would be too good to be true. My very first scooter was premix. Didn't mind it at all.

Maybe the SIP carb after all, but I'll keep looking.

Like I've mentioned numerous times… engine build stuff is annoying enough as it is… anything to help anyone avoid the pitfalls that I've experienced is a win in my eyes…

I'd try get the real deal, not that I'm a stickler for other brands/versions… but in this case dellorto doesn't fail to deliver…

Sorry, still have more questions. The clutch.

VMC 10 Molle Ergal is out of stock at SIP:

https://www.sip-scootershop.com/en/product/clutch-vmc-cosa-2-sport-ergal-10-molle-clutch-cosa-2_93246120?usrc=Clutch%20vmc%2010%20Mille

This one is available:

https://www.sip-scootershop.com/en/product/clutch-vmc-cosa-2-sport-ergal-10-molle-interlocked-clutch-cosa-2_93246130

My guess is that the second one labeled "interlocked" is for scooters with an interlock switch for electric start (which I don't have).

I'm ASS-uming that it will work anyway. There is also a steel version, but I would prefer aluminum.