Modern Vespa

While the FABBRI is 12.1oz. Just how much of a difference is that?...not much. Three of those blue springs together weigh in at .9oz.

And here's a picture of the FABBRI all assembled. I cleaned all the packaging oil off the parts with lacquer thinner, then used red thread locker on those four 6mm screws. They then got torqued down to 15nm.

In the picture, the FABBRI basket/primary is upside down on the left, with the FABBRI clutch portion of it right above it. The one to the right is the DRT. At the top is the stock PKXL clutch.

I've been super busy working another project that has 4 wheels during the day, so I've been working on the PK in the evenings. When using a combination of stock, DRT, Crimaz, and FABBRI parts, LOTS of shimming is going on inside those cases! I first had to shim the FABBRI primary gear (that has a DRT clutch primary gear attached to it) in the case. From there the DRT gear cluster needed to be shimmed in correlation with the loose gear stack (which happens to have a taller DRT 1st gear). The gear cluster was tricky to shim. I ended up buying a second spare bearing for the gear cluster so I could sand it down into a "dummy bearing". It made it MUCH easier to set up the end play on that cluster gear. Then I had to shim the kickstart quadrant so that it would line up with the loose kickstart gear....all the while taking into account of the thickness of the engine case gasket. I must have spit the cases 20-30 times to get it just right! Even though I had it apart that many times, it was never frustrating...just therapeutic. All this shimming would have been much easier if the instructions weren't all in Italian. I was pretty much shooting from the hip on figuring out most of it.

Here's some interesting weights of the PK and Vape flywheels. The PK is 2678 grams and the Vape is 1400 grams. That's about a 2 pound difference! Having a lighter flywheel should make life easier on the crankshaft.

And the Vape unit.

The Vape fan is much smaller than the Piaggio version. One has to wonder about the cooling comparisons between the two...

After the cases were buttoned up, I quickly did a preliminary mock-up of the cylinder and head. Since I had .5mm decked from the cases, and the 53mm DRT crankshaft came with a 1mm aluminum packer, I stacked 1.5mm of gaskets under the cylinder. The crank also came with a 1mm aluminum packet for the head as well. When all installed the squish was about a 1.8mm. Parmakit recommends a 1.2~1.3mm. It's easy enough to get down to the correct squish, but currently the BDT of the piston is about 1.5mm below the bottom of the exhaust and transfer ports. I'm not sure what my next step is going to be now...lower the all the ports with a dremel?...remove a couple millimeters from the bottom of the cylinder and install a much thicker packet in the head? I'd kinda hate to install a real thick head packer since I won't be able to utilize the "stepped head" design of the Parmakit.

In the picture you can kinda see the piston 1.5mm below the exhaust port.

That fan comparison is very interesting, does the Vape even touch the sides (so to speak) of the flywheel cowl?

A few weeks back I put an alloy Polini 130 on a mates motor, he had that flywheel as well. Had to get about 6 or 7mm turned off the inner edge to clear the transfers on the cylinder. I thought it felt heavy, was still 2.5kg after removing that chunk.

Lowering the ports won't make a difference so just leave them alone.

Since you brought it up, I figured I should see...and sure enough, the Vape fan does rub against the flywheel cowl. But seriously?!...do we expect anything less from ill fitted parts from SIP? So I was scrolling through their website last night, and (luckily) happen to see that there's an aftermarket flywheel fan spacer available. That takes some pressure off of figuring out what to do next. I happened to order the 3mm thick Crimaz stainless steel spacer.

https://www.sip-scootershop.com/en/products/spacer+crimaz+flywheel+cover+_22159600

That's frustrating. And oh so typical! I think I made a 3D file for Vader a long while back so he could get it printed at Shapeways. He bought one of those in the end though.

I don't mind spending a few more dollars on the extra parts that are needed, but yeah, super frustrating when the instructions don't mention it. Usually SIP have the parts that you need somewhere hidden in their website, but you have to guess if those parts that you need even exist in the first place. Then there's the whole wasted time and extra $$ that goes into shipping small bits.

Sometimes how I feel about SIP...
www.youtube.com/watch?v=cyWVPHoFGJA

The SIP spacer works well. I needed to space out the shroud on my '64 V90. Had to reshape it, shorten it and redrill two of the mounting holes to fit the small spigot case. Created just enough room to clear the flytech fan

sooooo it works well after you re-engineer it

Ha!

The inside of the clutch cover needed to have some material removed so that the clutch basket wouldn't run against it. It was close to an 1/8" that i removed. I started out with a thin 5" cutoff wheel on my angle grinder, then finished it up with a flapper disc and then a scotch bright disc. The clutch seems to fit fine without having to use one of those thick clutch spacers.

The PK specific 3mm spacer that Crimaz makes fits great! It's nothing fancy, just zinc plated steel. At least it will be plenty strong and I won't have to be concerned about bending it on accident.

Once mounted up somehow the math lies...with a 3mm spacer I get a 10mm gap.

No big deal at all, but there's about a 10mm gap for the screw that going through the fan shroud and into cylinder. I guess the Parma cylinder has a little bit different casting than the stock 125 cylinder did? Maybe I'll install a stud and a 10mm spacer in there. Like I said, i'm not to concerned about it, I just don't like having empty holes to look at.

I see the cylinder is on. How did the port timing work out?

Hi Jack, thanks for swinging by!

I don't know the timings yet. The cylinder is on, but only held on temporarily with two nuts. I had an idea last night on how to attach a TrailTech CHT sensor to the head (and not under the spark plug). So I'm want to get all of the aluminum cutting done before I start making measurements. That, and I haven't settled yet on what the squich will be. Parma specs out for a 1.2~1.3mm. Now don't laugh, but I'm really considering using the stock intake and SHB20 carb (instead of a Dellorto 25mil). Not to save money, but to (hopefully) get a much better fuel economy. That also means I'm hoping to use the stock PK125XL exhaust too. Reason being that there is currently no exhaust in production that will allow a spare tire to be installed on the PK scooter. I did fillet my stock exhaust a few weeks ago to see what it looks like inside. I drilled two 1" holes in the baffle in order to reduce back pressure. We'll see if A, I can sell it all back together (rust and all), and B, if the modded exhaust will even work.

Couldn't help laughing. Stock exhaust is not so bad. Once deciding on a non expansion pipe, then less important for the cylinder timing. The carb really should be bigger than the 20mm. Will still go but a lot of money spent on the engine to put a small carb on. If you have a 25mm it will be economic if jetted correctly. Could try the 20mm and see how big the main jet gets. If it really can't cope then it won't get rich enough at WOT.

1.2mm squish is what they say to be cautious. Tightest for that would be 0.5mm. The tighter it is the faster it will be. If mine I would go in the middle at 0.8mm.

Would seem like missing something to not change around that exhaust baffle while its open. What might work better?

Even on the Parma set-up instructions it recommends to NOT use a 20mil. I do have a 25mil Dellorto that i just installed on my PX215 (in place of the 30 mil that i just removed). I was hoping to see if i could squeeze out a little more fuel economy with a smaller carb. The other reason i was hoping to not use the 25mil is because there is no PK specific intake manifold that doesn't require cutting the frame. Though well within my skill level, i'd just prefer not to cut my frame.

...but all of that may all go out the window, and i might swap that 25mil on the PK...my frame isn't in the best of shape anyhow. I DO have LOTS wrapped up into this engine to only run a 20mil. When i build an engine i always like to heavily err on the side of over building all of the transmission/clutch/gearing, ect components, and then go milder with cylinder tuning. Probably 95% of my riding is just commuting on the highway, so i'm not after any sort of "fun" cylinder tuning...i've always been pretty darn satisfied with a boring stock P200 power. I was hoping to build my PK similar to the same performance as a "boring" stock P2 in fact. I don't foresee an expansion chamber though. I ride the PK quite a bit around the farm, and i'd hate to accidentally crush it.

I think it might be time for more late night window shopping over at SIP...

Oh, and what ring gap would you recommend with on the Parma? Out of the box it has about a .190mm gap.

And i don't know much of anything about baffles and exhausts. But maybe a couple additional holes would let it breath a little better so that it can support the Parma cylinder a little better? No big loss if it doesn't pan out.

I think a 20mm would be small but should jet in with a very big main. 25mm would be better. Maybe even use the 30mm. If it was a motorbike it would have a 35mm. Its mostly jetting that wastes fuel and smaller carbs are usually easier to jet well.

Maybe that exhaust could loose a baffle plate? Or half of one? I don't like the exhaust outlet. The diameter is good but the entry would be better if it funneled into the stinger. That one has just been cut off. Not the best for flow. Especially with the flow that will come from the Parmakit. Too much back pressure increases the WOT temperature.

Hoping to have a PK before long so researching myself. These are the ones I find that don't specifically mention chassis modification, not that I'd trust that entirely. The Sito looks to be th only one you can run a spare with. The right hand polini is for the 50's but i expect can be adapted with work to the 125 and run the spare.

https://www.sip-scootershop.com/en/products/racing+exhaust+sito+plus+for_24980000

https://www.sip-scootershop.com/en/products/racing+exhaust+polini+for_20020550

https://www.sip-scootershop.com/en/products/racing+exhaust+zirri+silent_40333000

https://www.sip-scootershop.com/en/products/racing+exhaust+zirri+silent_40360000

And from the Pipe Design website
https://translate.google.com/translate?sl=auto&tl=en&u=http%3A%2F%2Fwww.pipedesign.de%2Fauspuffanlagen%2Fsmallframe-v50pvpk%2Fs-box-pk-150.html
"As for all other racing and sports exhaust systems, the splash guard of the PK must be modified for assembly."

thanks for those leads Marc.
Ironically enough, that Sito+ exhaust has a smaller ID neck than the stock muffler...
I've used the Poilini banana before, but that was on my 103 Special. I was hoping to keep my spare tire under the cowl, but if won't fit with a banana.
I was under the impression that all things Zirri are high RPM?
I was hoping to find a (no longer available) NOS Leo Vince SecSys exhaust. It still allows the use of a spare tire.

From the description the first zirri linked supersedes the reviver one, if you trust descriptions. Also added links the PK s box 150 by pipe design.de

Also fixed the link to the polini right hand for 50cc and to the correct version of the s box 150 for pk

I know it's advertising and talking up the product, but I wish all exhausts were described as well as the PipeDesign ones!

Pipedesign will take in account all information you supply about your motor as they build your pipe. Fantastic construction and customer service.

I don't know how to translate German, so it's a no go on a pipe design. One of my friends said that he's had good luck with the LTH exhausts. It looks pretty sweet, but it would sure be a pain if I ever wanted to change a tire. I did weld back up my stock PK after I drill two 1" holes through an internal baffle. We'll see if it does anything. It was mostly just an experiment.

So after window shopping at SIP, I decided to switch over to a 25mil Dellorto. I robbed it off of my PX215 (and I reinstalled a 30mil back on the PX). I'm still not sure which exhaust I'll go with though.

I got some number for the timings... 126/174, and blow down is 24 degrees. Squish?...well my calipers show 1.14mm, my friend's calipers read 1.37mm. That's quite a difference! I thing I might contact the local moto engine tuner and drop my squished solder tests off at his house so that he can measure them with his expenses calipers. I used 1.6mm solder for my tests. It was very difficult to find that size in the US.

The page linked was already a translation WDC... you can also use Chrome which has built-in translation. Or for the best free translation, have a look at DeepL translator, it's very good even with quite technical things.

If you don't have thick solder, wind together a few strands of thinner stuff. Works well.

I just got some bits from SIP Friday afternoon, which meant that I could proceed a bit further...

I got a 1.5mm aluminum base gasket so test out. With cylinder and head torqued down, it shows that I have a 1.31mm squish. Parma specs out anywhere from a 1.2 to a 1.3mm. I suppose I could go tighter, but I don't want too much heat for a commuting scooter. So I'm going to keep it simple with that 1.5mm gasket.

I also got a Polini cast aluminum intake manifold to mount a 25 mil Dellorto carb on. Interestingly enough the intake area on the Polini is MUCH smaller that the stock PK steel manifold!

The Polini manifold would have to be "flowed" in order to get an optimal flow, but if you do that, you'll be grinding out to thin air! The only fix is to build up a bunch of weld in the area I have circled.

A better look at the bend in the intake.

With the amount of heat that a soool gun will create in the manifold, I decided to mount it to a piece of 1/4" steel plate to help prevent it from warping. I laid on LOTS of aluminum! It doesn't look that pretty when you weld smaller things with a spool gun, but it sure fills larger voids very quickly. That's as far as I got tonight with the manifold. I made sure it had cooled off completely before I inbolted it from the steel plate. It did a really good job of preventing warping, but I'm sure I'll have to go back and level out the flange area a little bit. I kinda wish I had built up weld around the transfers on the casse before I did all the previous work to it. Oh well, I'm not after max power anyhow (is what I keep telling myself).

I also worked on the front fork of the scooter as well. It's kinda difficult to remove the fork when there's a hydro line going through it, so I didn't remove the fork the completely...

At some point the fork stop had been damaged...multiple times. It looked like quite a bit of the stop had been ground away over the years.

I used a wire wheel to remove the paint. It's now a little more obvious how much of the fork stop it missing.

I blobbed on some aluminum with the spool gun. In the process I found some porosity. I'll then grind off the ugly buildup and bring it back into specs. It's something I've been wanting to do for a few years now. So I'm excited about getting it done.