Dio vs. Mina Corsa Piston

[Kenho21]

I recently purchased a "12mm Polini Corsa" cylinder/piston kit for my Minarelli motor from a vendor and was prompted by Sum-azn-kid to see if replacement pistons are available. I didn't see any direct replacements on the vendor's site, so I emailed them to ask where I can find replacement 12mm Corsa pistons. They replied with a link to a Corsa piston intended for a Honda Dio motor and said Polini doesn't offer 12mm pistons for the Mina kits, but that the pistons are the same for both, aside from the gudgeon pin size.

I took some measurements of the piston I have, which I would assume is the Dio piston they sell for the Mina cylinder, stating they are the same. I want to double check this and am wondering if anyone has a genuine 10mm Polini Corsa piston for a Minarelli handy and can compare measurements. Anyone?

Here's the measurements on the 12mm Corse "Mina/Dio" piston they sent me (if the calipers do not look like they're resting properly, they were at the time of measurement, just could not get a pic at the same time. Numbers displayed are pretty accurate though):

[ryan_ott]

The “12mm Corsa” I’ve had is the same as you have pictured, the piston is marked 2950. I’ve purchased a replacement 12mm Polini piston at one point which looks correct for a minarelli with the window and is labeled 2947. I’ll look and see if I can find where I got it from or the actual part number.

[ryan_ott]

I found this page but it lists the 2947 as 10mm... this is 12mm. I couldn’t find the invoice from it either.

www.scafutopistoni.it/pistoni/2350-pistone-polini-trasf-scooter-minarelliyamaha-75cc-2-tempi.html

[Kenho21]

Looks like you ran both of these pistons on your Mina Corsa? Did you notice and significant differences? I hope you can find where you bought the 12mm 2947... will definitely pick one up.

My 12mm piston has a 2950 stamp as well.

[Kenho21]

I wonder if this is the Mina version you have?


www.maxiscoot.com/polini-piston-corsa-70cc-piston-pin-12mm-piaggio-nrg-stalker-honda-p204-0690-3.html

[ryan_ott]

I found where I posted the image of where the piston came from. Just trying to find a listing for the replacement piston for it. 166.0108 is the cylinder kit.

Edit: 204.0840 is the piston. Keep in mind it has the grey cast rings, the Corsa has the chrome rings. You can use the chrome on it I was, actually both are chrome.


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[Kenho21]

Looks like it will have to come from across the pond.

How’d the kit run with the two different style pistons?

[ryan_ott]

I think the second piston ran stronger. It could be related to the dual chrome ringsI was running and a better seal or just in my head. I’m not talking about a huge improvement but I think the windowed piston did show some improvement.

[Kenho21]

That makes sense, in my head at least. The 2947 seems much closer in design to the 10mm piston designed for the Corsa kit. I'll probably assemble with the included piston and order the 2947 style if we can find a decent source for it.

Kinda miffs me that the vendor I bought from sells this as a kit without disclosing you're buying mismatched parts.

[190mech]

From a design point the windowed piston would be stronger then the notched piston as it has a continuous skirt guiding the bottom..Both of those designs are from the old cylinder reed engines,and a case reed engine has little use for either..

[808ministroke]

Somebody who has a little experience with both styles pistons and boars because the board are different as well let’s see I’ll take some pictures right now and show you



These are two pictures with both the main Erelli window style and the DO style you can tell in the second image if you look closely at that when I put on a flat surface holding down the mineral a piston that the other one rises about 2 mm off the glass also seems to be a m these are two pictures with both the main Erelli window style and video style you can tell in the second image if you look closely that when put on a flat surface holding down the mineral a piston that the other one rises about 2 mm off the glass also seems to be a mm shorter on dio this is from gulden hole. I’ll run out to my car and get it to boars side by side because that’s where the real differences lye

[Sum-azn-kid]

Thats great that the dio corsa piston fits the mina cylinder. I guess if I run the corsa in both my jog and dio i just order 1 spare piston!

[Kenho21]

Feb 8, 2020 17:45:21 GMT -5 ryan_ott said:

I found where I posted the image of where the piston came from. Just trying to find a listing for the replacement piston for it. 166.0108 is the cylinder kit.

Edit: 204.0840 is the piston. Keep in mind it has the grey cast rings, the Corsa has the chrome rings. You can use the chrome on it I was, actually both are chrome.


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I wonder if this is where you got it? www.scooterdynasty.com/cylinderkit70ccupgradeforminarelli50cc2t-1-1-1.aspx

[Kenho21]

This is the kit your piston came from ryan_ott: shorturl.at/orIYZ. Seems like it's a kit intended for Malaguti Mina motors. Do you think that's just because some of them use a 12mm pin (or seem to from what I've seen)? And I'm not sure if it's the Corsa or Sport version of Polini's cylinder. Kinda leaning toward it being the sport version.

Do you guys think using a Sport piston from one of these kits in a Corsa cylinder would go well?

[Kenho21]

Really trying to think of a way to make the Corsa work with a 12mm pin, but doesn't seem like there's an option.