Modern Vespa

The SS Minnow's Malossi Sport 210 was mostly built in an afternoon. It's proven robust, reliable, quick, and mighty fun, so I'm loath to mess with it.

But... Given the proliferation of new tech bits for Vespa engines, I've been fascinated for a while about just how good a PX style poweplant the average guy can put together himself.

For me, the BFA 306 is out of the question for this exercise. While it fits in a PX, it's really a T5, it can't be built into a set of PX cases, it's parts all rely on each other so there's no real mix and match and your stuck with BFA parts forever, and... well there's lots of there things I could say, but face it, it's too bloody expensive.

So I set myself the task of squirrelling away the parts for a Boss Hog build.

Step one was a 244 Quattrini Cylinder. That's been on the shelf in my office, teasing me for over 9 months.

Next I went looking for a donor 200 motor, or even a set of cases. I watched for over 6 month, and exactly none came up for sale. I thought I'd finally found one, but when the owner (a Brit living in Aus) heard what I wanted it for, he wouldn't sell, because he "didn't want me to ruin his engine".

So, onto plan B. In for a penny, in for a pound. Along with a co-conspirator, I bit the bullet and purchased a set of Malossi VR-One cases. Two days after they arrived, someone advertised a full, running, late PX200E engine for less than I've seen anywhere, 7 miles from home. (Yep, I snapped it up, that's a build for another day).

To get the most out of the 244, I was coveting the Kingwelle 64mm Stroke, 128mm rod crank. This gives a 260cc final result, and, well, going Boss Hog demands displacement. Sadly though, Kingwelle had no stock, and weren't about to for some time. Ginch came to the rescue here - a buddy here in Aus had just lunched an engine with a near new Kingwelle, and wasn't planning to rebuild it. So some shekels were exchanged, and 260cc's was back on the table.



Shiny

For this to go in the cases, it was necessary to mill the flyside out to 100mm. Luckily, I have a friend with a CNC mill in his garage.



Tonight at work I had a first squizz at how much dremelling I'll need to do, so the Quattrini finally came out of the box.

Interesting piston, no exhaust window



But whopping great cutouts in the sides



With 4mm to fill, I've chosen to go with a 2.5mm base gasket, and 1.5 at the head. Luckily, SIP do laser cut versions which are pretty close to bang on.



Marrying this up with the crankcase shows there's not a huge amount of Dremel work to be done.



Crankcase after markup.



A small blend for each of the main (side) ports, and to windows to expand at the top (bottom of photo).

There's an interesting protruding lip on the cylinder's fly side port.



It hangs out in space protruding over the flyside port( you can see I marked the overhang on the spacer in the photo further up). I'm thinking maybe the original cases have no meat there so the lip is built in for that. I _think_ I'l be ok to dremel it off and blend it and the spacer back to the line of the case port, but if anyone knows better, pleas let me know before I do something stoopid.

This won't be a super quick build like the 210 sport was, but it should be fun to see if a bloke in a garage can build a Boss Hog version of a PX vespa power plant.

Well - that looks flat out bad-ass.
Posted question on my own thread regarding CNC process.
Even better here.

Question: what are the basics for how you center the cases and then program for the cutting of the circle.
Did you use some form of CMM to tell the machine where your cases were - or did you just use a dial gauge to get centered, and then program in a circle cut?

This will be a very cool build.

Suspect I was typing the answers to your question over on your thread, while you were helping me out here!
https://modernvespa.com/forum/post2466422#2466422

Thanks for the case photos, links like the dremel can go to work...

And which part of this powerplant were you imagining "the average guy [putting] together himself"?

The parts where the Average Guy only has access to a CNC-upgraded bridgeport, as opposed to a proper tri-axial Tormach 1100MX

For a mere $7K you too can CNC this into being. Now, if I could just find some room in the garage.

Too funny, obviously I'm wayyyy below average.

Now we know what you're building there's even more questions. Starting with, what durations do you get with the 2.5mm packer and 64 crank? What exhaust? Stator type? Primary? Reed block? And the most important, which carb (please say not less than 39mm)?

Oh boy.. this sub-average joe is looking forward to seeing this run!

If only I had a garage that big.. and a budget big enough for that cnc mill.

Looks like you're well on your way to being the boss hog with this px engine.

Ha. The CNC mill is a nice toy to have access to, but I could have just jobbed it out at an engineering firm, bought them pre-spindled from Kingwelle, or even just jigged up a rotating arm for my dremel. I'm expecting Ginch along any moment to attest that I am indeed very average (or below!).

Jack, the packer dimensions were decided after lots of "research" reading google translated pages of G.S.M., talking to someone who went with 2+2, and some correspondence with Ben from vespmoto.de . The carb is a Keihin PWK Airstriker 35, again after much correspondence. I'll happily do a map of the ports at my desk before I bolt it on, but the 2.5/2.5 mix has been the winner for those that have built so far looking for a long legged tourer.

Exhaust will be starting as a Pollini box. I may go something more exotic later, but I want a simple, sturdy basis for getting it dialed in.

Reed will (currently) be the Malossi provided one, with a MRP 35mm top. I'd prefer a Tassinari VForce 4, but there are no housings available at the moment. I may buy the bits and make a housing if I have time.

Gearing needs a post of it's own...

I always loved watching the Dukes of Hazard, watching the General Lee jump and fenders crease, then next scene it's fine. And Boss Hog chasing them around. But of course my favorite was Daisy Duke.

This'll be fun to watch too

With the right set up resembling the tv "boss hog" (always smoking and imminent heart attack) can be easily avoided.

The m244 is a tourer in terms of its porting. The 64 crank does make that a lot sportier. If GSF say 2.5/2.5 then likely good, as they use more of these than anyone else. Actual port timing of your kit would be nice to know. For perfect balance some Dremel work is probably needed but unnecessary on a 260.

Many run these on SI carbs and are quite happy with that, so the 35mm is getting up there. A 39.5mm would be less economic but is 30% bigger. However, without a VF4 block it wouldn't perform.

Polini box is going to be like sticking a cork up it. Check the tail pipe. With the 260 it will need to be 25mm ID minimum.

Once running you can decide how you like it.

It's fat, shiny, loud, money grubbing, and gonna blow smoke. Sorrell Booke's antihero seem the perfect moniker.

I'll get you some hard data on the cylinder soon.

The Polini box is surprisingly popular over at GSF for this use. I'm similarly sceptical, but it should give me a base for dialing in. I'm not afraid of cutting and welding to get it breathing better, and wont be surprised if a serious pipe goes on later.

Got a start on roughing in the dremeling after work tonight.

Matched the spacer to the flyside case, then marked up the redundant potrusion




Then de-lumped it. More to do here as it needs to be matched back to the case port.



Flyside port is underway. Again, more to do, it needs a little more matching, and then a proper polish.



Lots of work to do, nice to be underway.

Please put it in one of your smallframes?

Just be sure the tail pipe is 25mm ID. If less the shiny kit might get less shiny very suddenly. 35mm carb isn't the biggest but bigger than most run with a box pipe.

Gently smooth out all the casting lumps being careful not to change the shape of anything. Radius that casing edge near the fly side bearing.

What gearing did you buy?

This one? How hard should I hit it?

They are your expensive casings. Square edges make turbulence. This is bad for flow rates. At least 1mm but could be up to 4mm. Harder to put the metal back and unlikely it will notice for road performance anyway.

Nice work there Craig.
Stuart runs a megadella L compact on his quattrini and its dream.
Like Jack said it has a nice large ID outlet diameter. Just allows those hot gases to escape that wee bit easier!!

Well if Craig is average then I must be very average.

You're certainly tempting me to get mine out but I have another motor I must build and get to the new owner first. Plus a house to renovate....

Craig, that's all looking great!! For everyone else, the way that I milled out my VR1 cases for the 64mm crank was to laser cut a 6mm acrylic template and use a double flute router bit to mill out the cases, dropping the depth a couple of mm at a time. It was nerve racking but the end result worked like a charm.

Genius Stuart!

The quality and variety of home brew machining around this forum of late is amazing.

I'd still like to get my hands on a lathe, but that's pretty far down the priority list.

All the GSF guys take that edge off - that you have circled in red.
I skip all the German writing and just look at the pictures - so it's easy to remember.

I'm deep down a rabbit hole myself on a mill right now.
Likely deserves a posting...

Very nice work on the cases as you prep.

Stuart - ballsy router job. Don't you have some kinda mill in your shed?

Great thread.

I have a CNC router and laser engraver (at work) but this required the finesse and delicacy of the hand held trimmer. Slow and steady won the job!!

Man, I wish. Smallies are all on hiatus, because I had to get out of the workspace I was hiring, so everything is currently stacked up in a storage room under work. I was hoping to find a new workspace over summer, but I've been to busy "working" at the skydiving club on weekends.

I only really have enough space to work on engines at the moment, so I'm trying to keep some momentum.

We've just been stuck in another lockdown, supposed to be only 7 days this time, so I'm doing some porting when I get a chance, since I'm stuck going into work and I'm the only one there.

Married up the piston, cylinder, spacer and case for the first time today. I still need to rough out a little more on the flyside main intake to fully meet the piston window.



It'll be fun getting that line cut straight.

The other side of that port is a problem. There's a (about) 1 - 1.5 mm lip/step going from the existing case port to the spacer and cylinder. I'm in a quandary if I should blend just the spacer up to the port, blend both the spacer and cylinder as lightly as I can, or just leave the step.





Tricky.

Left it alone today, and got a start on roughing in the blend for the sharp edge in the flyside case. Thoughts Jack? I can go further, I just figure it's better to check with the brains trust before I go to far or hit the wrong shape.



My gearing was all finally introduced to each other today too.

A nice mix of German and Italian

Snuck in a little more time this afternoon while waiting for a backup to finish

Left rear corner is now roughed in



and it aligns nicely with the piston



I'm tempted to smooth the initial inlet ramp a little more at the rear corners.

All looking plenty smooth enough. How's the big half looking? Not sure the piston comes down that far with the long rod but good it all lines up.

Some exotic looking gear box. 25/62 primary is a tall order. If anything can pull it this can. How all the other cogs compare with stock 200?

12-13-17-20 into 55-40-38-35. If it wont pull it I'll switch the clutch out to a 24.

Thoughts on the step on the other side? I figure since it's blocking flow it's gotta go.

Haven't touched the other half of the casing yet, going to be a slow and steady job. I assume I should blend the sharp step on that one as well.

Yea haw Bo! - really nice looking work.
My $.02:
I would give the cylinder a light blend - and not worry about it after that - or just leave it be as is.
Don't think it will affect performance.
Would be careful about leaving myself too small a sealing surface and such.

There are a number of posts/ YouTube videos I have seen regarding imperfect matching of cylinder to case - with no ill effects.
The basic is - there are just other bottlenecks that are normally the actual limiting factor - and a lot can flow through the area you have the mismatch on.

Like the gearbox. Tall 1st and 2nd, short 4th on the tree. It has every chance of being correct. With a 24 cog to fit that ring gear, all bases are covered. Are you going to take the pawl off the gear selector with that indexed driveshaft? Or keep both?

Casings are flowed enough. Take the lip of with the packer. If the nicasil gets chipped it will set the build back a while. What this will be doesn't really require high flow on the transfers. No harm in it but when we know the port timing it will be low and more pressure dependent, most likely.

Would start looking for a real exhaust, once run in I think it might run a bit hot with the Polini box.

Pawl should be fine off, if it starts jumping I'll try one with.

Working on the clutch side port today.

I couldn't figure out a way to line up the piston properly with the eccentric ports, to I bolted it all back in the flyside, then broke out the laser to let me mark the piston skirt where the casing join is.



Next I marked up the part where the metal was in the was of the air.



Rough cut...



Getting close



Finished. (Note the red mark on the piston skirt for alignment)



Time for the top ports.

Damn - work looks excellent.
Curious - what bit are you using to grind with?

Noice.

Your laser alignment bench looks suspiciously clean...

Lockdown. Only I.T. allowed on site at work. I have 50+ desks to chose from. Ginch gets very annoyed when I trot out my stock truism about tools. "Good tools are their own reward".

I've built up a pretty good collection of metal removal implements, for this task I grabbed a job lot of them and took them to the basement at work (couldn't be bothered dragging the compressor out, so I left the air die grinders behind and went electric):



I used the power file with 40,80 and/or 120 grit to rough in, then the die grinder to get closer to the shape. For fine work and sharp corners I switched to the Dremel with cutting burrs. once I was really close to the shape I used a combination of small and large sanding drums (lots of them!) and sanding disks on the Dremel and jewellers files. Once I was settled on the shape I switched to hand sanding with strips of emery paper, stepping down from 240 to 360 to 600 to 800. Next, back to the dremel, first with scotchbrite buffing pads ($10 a throw from Dremel, or $17 for a bag of 30 from ebay, and they last under 90 seconds each...), then onto a polishing head with cutting compound. (That last step may have been overkill...). In all I went through about 80 bucks of consumables.

Considering the fit and finish of the $50* cases out of the box,



I reckon they've come up ok.



I could keep going, but I think the law of diminishing returns has kicked in.



Time to start building.


(* Wife reported price. Actual retail may vary).

Gorgeous work! And great deal on those cases!

*Second chuckle of the morning.
Exceptional fit.
I've got a power file - but never thought to use it to do rough carve in.
Someone turned me on to the large flute die burrs.
They can bounce around a little but don't seem to load up with aluminum at all.
Assume you have these in your arsenal already...

I tried bar soap on the burr and it helped enormously. I was a bit surprised it made so much difference.

When I'm not being lazy - I use that method on my smaller burrs.
The issue is - If I am welding - and grinding something back - I don't want to contaminate the metal with soap or oil.
Solid trick though - I agree.

Just read through this...
*mind blown*