Modern Vespa

Hi all, a friend had recently split the cases on his PX150 from 2005 only to discover the horror that awaited him. Lots of cracks!

So now he is on two minds, to try and fix the original cases or go for a new Pinasco 125/150cc cases.


I know this community is very resourceful so I'm relying on the experts to help us decide what to do next with his build.


Brief history, the bike was imported from Greece, and had a DR 177 on it with a Cosa clutch, everything else was stock.

The auto-lube failed causing the DR to hard seize.

So he upgraded to a Polini 177 kit complemented by Mazzucheli crank and SI24-24 carb, and Simonnini exhaust.
Also all new bearing and seals, and had that fitted by a local motor shop.

You'll see in the pics that the mechanic clearly did something wrong when closing the cases together.

The funny thing is the PX ran great and had a lot of power. The only symptom was that he had a oil leak somewhere from the bottom of the case and was quite smokey through the rev range.

Currently the carb setup is 55-160 idle, 160-BE3-128main.

Just buy a set of used cases or a old motor and swap over the parts. That shouldn't be all that hard to find as the cases are pretty much the same through the years of the PX/P series from 125-150cc. Just depends on electric start or not.

Thanks for the reply, so your saying the old cases cant be fixed by welding?

Cause finding a second used motor or cases is next to impossible here. It can be imported but the cost comes close to new Pinasco cases.

My friend is inclined to purchase the Pinasco cases from scooter-center, since they now have a 10% discount till Monday.

The trouble is with the pinasco case, even the ones meant for the 150cc uses a 200cc crank. So the old crank can not be used.

So he is on two minds what to do. Any advice appreciated.

Anyone using a Pinasco cases with a Polini 177 by any chance?

You certainly can give TIG welding those cases a try. You will have to media blast them first, then TIG weld, then machine the sealing surface for the clutch. just a guess here, but your shoulder washer for the clutch came apart and went into the gear box, those parts jammed between the output shaft gears and case pushing all gears towards the crank.

no chance on using a small block kit on a big block case.

Do not use your old cracked cases. I've been tig welding for 25 years, and where those are at....very difficult to get everything all aligned again. Buy new cases, or a set of used cases. It would be cheaper. Scott

That's absolutely true. If the are not true, it's not going to work. If it were me in this situation, I would just buy new. But if this guy had time and the tools, it might be worth trying.

One more thing...

>99% of the time that autolube shoulder washer cracks from being installed backwards at some point in its life. The chamfered side must be facing the crank not the clutch, otherwise it gets torqued down onto a slightly conical surface which strains the metallurgy and some day, boom! down the pieces go into the gear case and if you're lucky, the rear wheel doesn't lock up hard.

That is some good info there. That didn't cross my mind. Good observation from pdxjim. I will have to watch that one myself.
I will reiterate what I already said....do not try and weld. Scott

I've seen Miller's welded up and machined in a lot worse condition. The p-case is not rare and can be sourced used or new, a Miller on the other hand is not.

Sjanuary: ^^^
If you ever find that shoulder gear backwards, do not turn it around and reuse, it's already compromised. They're not expensive, just replace it and have one less thing nagging at your peace of mind while tearing down the highway.

If I'm going to go through and try and weld a case as the one pictured...it better be a "one of a kind."
I don't think a p150 is.... have a great holiday weekend.scott

Interesting info.

My friend decided to go for new Pinasco master crankcases for 125/150cc. With the original rotary valve.

Now the thing is will he be able to fit most of the stuff he already has?

The Polini 177, simonnini exhaust, the original stator amd flywheel.

I see that even the 125/150cc cases are meant exclusively for a 200cc crank, so can the 177 kit be used here or not?

I'm curious how the cracks got there in the first place.

I'm curius too Jim.

Right now all the blame goes to the mechanic that did the previous rebuild. I'm guessing he overtightened the cases and probably fitted the washer behind the clutch wrong.

Yes it can. The 150 case has the right stud spacing for any 150 - based cylinder kit.
The difference is that the 200 crank has a 5mm longer conrod, that's one reason the 150 crank won't fit. The other is that the 200 crank has a lip on the clutch side - which makes the rotary valve sealing surface wider. The 200 intake under the carber is also wider than a 150.

So if you were to fit the 150 crank (and it would definitely fit the space) you'd find there would be a small gap at the rotary valve. And of course the piston would stop at least 5mm short of the top of the cylinder.

Did you ever consider a set of LML cases? I realise that you need to be careful, but you can get good quality ones.

Ginch, thanks for the info. He will order a 200 crank then we'll see what spacer to use to compensate for the longer conrod.

swa, I tried to persuade him to go for a LML case, but he has already invested a lot in rebuilding this vespa so he wants it done properly.

SO we are planning on making the order tonight from scooter-center while they still have the 10% discount.


I attached pics of what he is getting so far, I think it will be enough for this build to be completed.

If the case is made for a 200 crank, then you will not need a packer at all, just a normal gasket.

BUT - and I should have mentioned this before but forgot, sorry!
He will need a conversion bearing for the gudgeon pin. The 200 piston has a 16mm gudgeon pin and the 150 is a 15.

SCK have this one - https://www.scooter-center.com/en/7672564/small-end-needle-bearing-tkrj-15x20x17-8mm-vespa-px80-px125-px150-cc-for-using-px200-crankshaft?number=7672564

However since the original bearing for a 200 is 16x20x20 then there may be quite a bit of float sideways... I'd be more comfortable using this from LTH... only 1mm narrower instead of 2.2 at 15x20x19.

https://www.lambretta-teile.de/Small-end-bearing-15x20x197mm-conversion-PX200-crank-with-with-PX125-barrel-Vespa-PX

Ginch, surely the 110mm rod is still going to put the piston 5mm further up the cylinder, or does the Pinasco case take up the extra 5mm at the base?

Then there's the extra 1.5mm to consider with a longstroke crank.

Yes I believe they do have that extra material. They don't explicitly say that but I'm sure that's correct. Ah yes of course you're right, I forgot that as well!

Given some of the reviews on these cases, I'd be paying particular attention to the way the bearings are fitted... be sure to use the correct Loctite (or similar product) to make sure the bearings stay in place.

Its not a problem to add spacer and get the timing right kn the cilinder, the thing is what will be the easiest setup to get a polini177 on a Pinasco case with a 200cc crank?

I just found a Mazzuchelli crank for 200cc with a 57mm conrod. Does the 200cc vespa come with 57 or 60mm?

The 200 is a development of the 150, the changes made were relatively minor.

The normal stroke for all largeframe motors (apart from the T5) is 57mm. You can fit a 60mm stroke crank to either motor and it'll add a bit under 10cc - so 187cc for the Polini 177.

That crank from LTH will work, but it's just a normal crank. The other one, the 60mm from SCK, is cut a bit differently so that the intake stays open a little longer each revolution. That, as well as the bigger area intake in the Pinasco case, will make more power from the same cylinder.

It shouldn't be any harder to set up than it was last time on the old (cracked) case. You can put it all together with the 1.5 packer in place of the normal thin gasket.

Thanks again for the reply Ginch

Somehow I always though that all PX200 had 60mm cranks.

We are definitively going for a long stroke 200cc crank.

Now we are puzzled cause we saw on the Pinasco case instructions that pinasco recommends using a 5mm spacer for the cylinder base while using a stock 200cc crank.

So that would came to a 6.5mm spacer if we go long-stroke?

I didn't see that! What an odd way to do things!
SCK and LTH don't have that in their descriptions... but I now see SIP does which is much better. In fact it says the packer and bearing is included in delivery. And now I look a bit harder the SCK and LTH have those parts shown in the pictures.
Sorry I seem to have given you a couple of incorrect bits of advice earlier!

None of them tell you which small end bearing is included. That bit of advice still stands however and I think the 15x20x19 is the right one.

If you want more power the longer 60mm crank is a good thing. The longer inlet duration of the racing Mazz crank will help too.
With the 60mm crank the port timing will be stronger but with the longer conrod (110mm not 105mm) the port timing loses a bit of this advantage.
With the extra cc (187 not 177) the compression will go up. This is not always good for power on a 2 stroke.

When you get it all together, for the best compromise, I would set the height of TDC to be 0.5mm below the top of the cylinder. So when the cylinder is held down the piston doesn't quite get to the top. This can be measured with feeler gauges to be accurate.
Going to all this expense it might as well go faster

Jack could you please expand on this a little? I had read that a longer rod will give you more port-time area, as well as more crankcase volume. Both of which ought to add up to a good thing - or do they?

Longer conrods do give more crankcase volume, reed blocks also give more volume. Together these noticably reduce the transfer pressure, which can then handle higher durations with less losses. All good. Long conrods need the barrel set even higher to compensate for these factors. Only point of concern is the head and squish, which might need the head modifying, as there is now less scope in the transfers. In short longer conrods end up being a good thing.

Doesn't the head/squish remain the same regardless of the length of rod? Assuming no change of stroke.

To make the long rod work better than without it the barrel will need to be set higher. Reducing the pressure without increasing the duration would not go as well. Increasing duration by raising the packer will drop the squish. Very difficult to quantify the loss of crankcase pressure. Messy and not fantastically accurate to measure. If you have any data on this it would make interesting reading.

Just a small upgrade, we got the Pinasco master crankcase with a Mazzuchelli racing long stroke 200cc crank.

Scooter Center confirmed that with the Pinasco case you get both the 5mm spacer and a conrod needle bearing that will fit on a 150cc gudgeon pin along with everything else thats on the picture on their website.

We also bough a 1.5mm spacer to adjust the barrel higher for the 60mm stroke, so will see how it goes once we get the parts.

I also got a SI-24/24E and a Pinasco expansion exhaust for my 150 LML that runs the Malossi 166.


Thanks again for everyone's help and advice

We expect pictures of the build Jocco! Hope it goes well.

Well, the pinasco crankcase arrived, and sadly immediately we noticed a few issues with it

First, there are some small dings in the area where the crank seal should sit, and secondly the finished quality really let us down.

But this build needs to be finished so now we need some help on how to set up the 60mm mazzuchelli crank.

We have a 1.5mm base spacer to compensate for the longer crank, but what else needs to be adjusted?

The transfers, do we do something with the head?
How much squish to aim for, and how much compression is ok?

Again, any advice is appreciated.

Not sure if you have it set up yet but saw there were no replies so I thought I'd offer some insight on the easiest way to get the cylinder and head set up properly so that it flows well.
First, I install the rotating assembly(crank and piston) without the rings and then lower the cylinder onto the case so that I can easily rotate the crank. At a minimum you want the exhaust port to be fully open at bdc. With a long stroke and long rod this won't be the case. Use feeler gauges on either side of the cylinder to raise it until the piston drops below the bottom edge of the exhaust port. This is the min size packing plate you need. Install packing plate and raise cylinder to Tdc and measure where the piston is in relation to the top edge of the cylinder. A good squish for 200 and under cylinders is 1.5mm. Given typical combustion chamber volume this won't be too high of compression and provide good performance. To get the squish, you may need to shave the head, shave the cylinder, or a combo of both.
This is an extremely simplified and basic setup procedure but typically works well for those that don't typically do advanced engine building but don't want to destroy an engine. It's well worth it to also measure your timings for piece of mind. 175 exhaust 125 intakes have really good midrange without being too peaky. Above 185 and you're going to be in and out of the power pretty quick.

Good luck! Look forward to pics!!

Joe

Thanks for the reply Joe. Nice and simple explanation.

But the vespa is done and is now on the road.

My friend decided to take it to a new mechanic, one that previously rebuild an another friends vespa.

He took his time and did some porting on the Polini 177 cylinder and also on the new Pinasco case.

He also did some work on the carb opening on the case.

Now I dont know if he widedned or raised nay transfers or exhaust opening, bu I have a few pics of the porting work.

The vespa is now a torque beast, pulls nicely all throughout the revs.

The just used the 5mm spacer that came with the Pinasco case, and the mechanic decided that the additional 1.5mm spacer was not needed.


Pics and video will follow

More pics of the work done to the Pinasco case and the Polini cylinder