Modern Vespa

Hi all. Is anyone running one of these kits?? A friend has it on his PX (bolt on) and now he needs a full engine overhaul. He also has a longstroke serie pro crank he had bought along with a parts bin (we don’t know which one and it’s timings) which he wants to put in. The kit has the “Genova 810” cylinder head and the weird fully open piston. So, what packers, head, rotary pad opening, timings, etc. do we need for this kit to work well?? He also runs a SI24/24 and a chrome SIP Road 2.0...

Got any pictures and measurements? Crank is probably for sportier use but if that's what he has it will work.
Round out all the edges on that weird big window piston to have any chance it won't crack.

Will do, as soon as he brings me the motor and the parts. Since it needs new rings, which are pretty expensive now, I thought that maybe a new GS “Polini” 69mm piston would be a better choice??

How much is just one new piston ring fitted on the old piston. Doesn't really need two.

Both rings are shot (it’s the piston with the top “L” ring). Ring gap on both are about 1mm - 1,2mm. Set of rings cost 50€ - 60€ and availability is slim. Pinasco replaced them with the new type rings / piston. So that’s the main reason we’re thinking for a GS piston + it will be more robust...

Choices are few. With the L shaped ring you have to buy both. GS is not showing stock for the 69mm piston. If the piston hasn't cracked yet, then new rings are an option.

Piston is available at SIP. It will be ordered through a local supplier who works directly with them. I know rings are an option, but I am a bit afraid on the reliability of the piston...

You have a link? Can't find it on SIP but that doesn't mean its not there

Here it is...

https://www.sip-scootershop.com/en/products/~/products/piston+grandsport+for+sip+_12039200

You may be worrying too much about the possibility of the Pinasco/Asso piston cracking. Does anyone actually known the fail rate of these pistons vs others? Are they really that bad, cos if they are, I'm also interested in the GS 69mm if it does a good job in a Pinasco setup?

Thats a Polossi piston! It should fit. It won't line up properly but I expect it to be close. If you have an old 68.5 Malossi piston around the shop, it will be possible to check the side window alignment before you buy the 69.0mm Polossi one.
If you take the piston out and there is no damage, then as swa45 said I think the new rings on the Pinasco one is the better option. When it does finally break he can buy a complete new kit. Malossi Sport?

Tried the Malossi piston and it lines up almost perfectly (it will need a bit of grinding) so while waiting for the GS piston and the packers to arrive, we decided to O-Tune the cylinder and try to get as much as we can from the kit, until my friend can afford a Malossi kit...

Now this is interesting MV's first ever Pinossi 225.

With the 60mm longstroke crank this has great potential. Will probably be nearly as quick as a Malossi Sport if the port timing is upped a lot. The early Pinasco kits are almost an ally stock cylinder in terms of port timing.

Have a measure of the ports from the top and we can see how many mm (and it will be many whole mm) it all needs to move by.

This is good experience for you with cutting Nicasil too (You'll be in that T5 172 next). Chamfer all the edges and round corners and it will stay attached.

oh gosh this is looking good.

A bit of progress (not perfect yet). My friend also brought me the engine today and tomorrow I'll split it, so as to match the "new" ports to the cases...

this is looking good.. ill follow this with interest!!

A bit of progress today. Engine split and porting started. I will also JB Weld the "fake" ports which are useless anyways...

This is looking great keep the photos coming!

Fine work as usual. Going to need a base packer with that. Easier to grind it all at the same time.

Cylinder porting and polishing done. Inlet's "drill hole" smoothed out and I'll also match the carb and the "tub" to the inlet. Waiting for the piston, the packers and few bits and pieces. I've also rebuilt his cush drive (4 of the 6 springs were broken). I always use original Piaggio rivets cause the ones that come in the F.A. Italia rebuild kit are crap. A bag of 50 rivets is only 1,90€ at Piaggio (wholesale price)...

Few photos...

Safis - killer job, killer photos.
Hadn't seen the drill and cut method - maybe this is the norm but it never registered with me if that's the case. Great trick. Thanks for sharing.

Gotta love JB - weld.

Your friends scoot is going to fly. He's not gonna know what hit him.

Fun thread.

-CM

All looking nice

While doing that inlet 10mm could come out of the back.

What is the expected port timing and squish?

Thanks guys!

Jack, I’ll not touch the rotary until I measure the crank’s timings, since it’s probably sportier than we want it to be...

Sorry, novice here; is JB weld really strong enough to be used like this?

On most occasions, yes. But even if it separates from the cases, on this particular cylinder there's no way for the piece to go anywhere cause it'll be held / blocked by the cylinder's skirt...

Looking Grand now I want one for myself!

Can you share more about your JB Weld process, we're interested in dams or fixtures to hold the weld in place you may have created.

Right, good point about the cylinder's skirt. Excellent workmanship, BTW. I'm interested to see how this build goes.

@hibbert: I just use a center punch and make many small dimples...

GS Piston (beautifully made) and bits and pieces came today. No packers (I had ordered 0,8mm packers for top and bottom but no show). Maybe I should reconsider now. Put in the bearings, clutch seal, crank and piston (chamfered all sharp edges) to measure the timings I get. Without any packers, the piston is at zero deck, just like the stock cylinder with a longstroke crank. Timings following as they are now and how they would look with a 1,5mm packer at the bottom. As for the cylinder head, I'll machine the stock Pinasco to match an MMW head I have on the self...


No Packer

Raised Cylinder

Our trusty, 35 year old, handmade crank puller :)

Crank in

GS Piston (made by Meteor)

Top view

Matched boost window

Zero deck

Flywheel side port

Clutch side port

Clutch side. Passes through the port at BDC. Should I grind it??

Piston does look nice. I would leave that bit on the piston. They are a little thin on stability without the Polossi cuts in the windows.

How did the rotary timing work out?

With the 1.5mm on the base the transfer timing looks a little long but as they are small ports, longer duration will make up for lack of width.
With this though the blowdown is very short. Which means it will be like a diesel car. Feels really quick at mid rpm but nothing there when opened up.
Take the exhaust port up from 174 to 184 and it will be a very solid tourer.

Didn’t touch it yet. These are the timings I get with the crank he got. If I open it up won’t the inlet duration be even bigger?? I’m thinking on keeping the 0,8mm packers and raise the exhaust port a bit...

Is that your rotary inlet measurement, 164 degrees total? Needs to be more than that. Is nearly stock.

Even with no packer at all, the blowdown is still be too short. Transfers will be ok there but won't make the best of all that work you've done. And it will go very average.

My best suggestion for the easiest job. is a 1.0mm packer. Skim the head flat and that will give a ~1.0mm squish. Exhaust port is going to have to move whatever you do. With the 1.0mm packer the exhaust needs to go up 2.5mm to 34.5mm.

Thought it would be a lot. Great Nicasil Dremel practice. Lots of room to make mistakes then clean it up in 2.5mm. As its not really for speed just focus on the centre 20mm of the exhaust port and blend the sides down.

Exactly, 164° total. So, crank is probably a stockish 60mm?? Should I go for the 10mm on the rotary as you mentioned before?? 1mm packer it is then...

Thought the crank was going to be more. 180 will be a good amount. If you take a few mm out the front and 15mm out the back. It will be about 56/125 and that will go well.

This 24/24 carb. No filter/vortex. Box exhaust?

Jack, won’t 15mm be too much for a future Malossi Sport?? Carb is with original filter (drilled heart) and a chromed SIP Road 2.0 which might be changed cause it started falling apart from the inside...

Is almost a 1mm per degree. 164 + 15 is 179. Few extra out the front maybe 181 or slightly more, total. Just right for a tourer. Its basically a stock crank if its 164 degrees. They are normally about 160 in a P200.

I assume it would be the same thing, let’s say by cutting 10mm of the crank and opening the rotary accordingly?? I don’t want to open it too much because it’s a bit rough at the back...

Its the same thing but the crank needs to be cut at the big end bearing. Really hard to do well but if anyone can, you can.

I see what you mean about the rough pad from the picture. Take 10mm out the back, a few out the front and maybe some off the big end. If it ends up at 175° it will still go fine.

I assume, you mean where the "opening" starts (green arrow) and not where it ends (red arrow)...

Yes the green arrow. You might get a few degrees out of it there but its a lot of effort for not much.

Productive day, today. Machined the head, the clutch cover and 2 levers (double o-ring), cut the crank, raised the exhaust port, opened up the rotary and matched the carb and the carb box to the inlet. New timings with the 0,8mm packer. 1mm packers were not available and because we are in a hurry for a planned roadtrip, we'll have to do with this one. Also, since the chromed SIP is dead, we decided on the new FACO Power BOX (already tried by 3 friends and my supplier). They are very pleased and they also got more top speed that the Road 2.0 they had before. Only downside is that it's more noisy, but so is the chromed Road 2.0 he has...