Wich one is the correct piston for ac3 engine?

Per discutere di tutto ciò riguarda il mondo dell'Ape Piaggio anni '50, '60 e '70 (telai A, B, C, D, E, MP) / To discuss all about Ape Piaggio's world in the fifties, sixties and seventies (A, B, C, D, E, MP chassis)
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DavidRaeder
Apista aspirante
Messaggi: 8
Iscritto il: 23 maggio 2017, 5:12
Ape owned: AC3
Località: Curitiba, Brazil

Wich one is the correct piston for ac3 engine?

Messaggio da DavidRaeder »

Hello,
My ac3 engine was working with the deflector nose shape piston like the oldests models but as i saw on the parts manual the ac3 piston is the same as the ac4 model with a smooth rounded head.
I am not sure if the cylinder and head are the same for both and if i can change for the ac4 piston. Maybe i am wrong but i think that if Piaggio changed the piston there is a reason, maybe better performance, am i right?
Ape AC3 1961 - Vespa VB1 1960 - Vespa PX200 Elestart 1988 - Vespa Super 150 1979 - Vespa GS160 (replica)
*brazilian versions
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Miami
Apista apprendista
Apista apprendista
Messaggi: 51
Iscritto il: 9 aprile 2012, 21:57

Re: Wich one is the correct piston for ac3 engine?

Messaggio da Miami »

My ac1 had the deflector piston like yours but the spark plug threads came out of the head and i couldn't find a good replacement so i switched to the flat style piston and head. You can keep the same cylinder but make sure you check your ring gap clearance or you'll seize it if it's too small or lose compression if it's too large. Been running with the later style piston and head a few years now, no issues.

alex
DavidRaeder
Apista aspirante
Messaggi: 8
Iscritto il: 23 maggio 2017, 5:12
Ape owned: AC3
Località: Curitiba, Brazil

Re: Wich one is the correct piston for ac3 engine?

Messaggio da DavidRaeder »

Hi Alex, do you notice any improvement whith the late piston? Is the cylinder head the same for both or must changed as a pair?
Thanks
Ape AC3 1961 - Vespa VB1 1960 - Vespa PX200 Elestart 1988 - Vespa Super 150 1979 - Vespa GS160 (replica)
*brazilian versions
%(^
Miami
Apista apprendista
Apista apprendista
Messaggi: 51
Iscritto il: 9 aprile 2012, 21:57

Re: Wich one is the correct piston for ac3 engine?

Messaggio da Miami »

sorry for the late reply. no difference in performance, the head does need to be changed with the piston (you can keep the same cylinder). Replacing the original carburettor with a modern dell'orto made a big difference in the way it runs, starts very easy, idles great and runs much smoother with better response.

alex
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