[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)

Thanks for the reply Jan Thiel.
Health.

Nombre de messages : 106 Localisation : Biblis Date d'inscription : 14/01/2017

Hallo,

as i got help here many times by Frits, Jan Thiel and others i want to give a humble feedback.
A few pages back we discussed the PWM-triggered Powerjet of the Aprilia RSW.

With the reference of a former GP-mechanic for a not itemised Honda origin of the parts used by Dellorto i managed to get 2 NOS solenoids after months of inquiries.
They were distributed by Honda HRC for the last generation Honda RS 125 and 250 Keihin carburetors.
125 and 250 got different part numbers but differ only in the lenght of the electric wires.
I checked the lenght of the push rod and the mounting holes. Exact the same as on the Dellorto works carburetor.
The solenoid is a push type, valve is currentless open and got a black rubber tip to close safely.
The part number can be seen on the photos.

Best regards,
Bernd

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Dell'Orto bought them from Keihin!!!

Nombre de messages : 5 Localisation : France Date d'inscription : 21/03/2020

hi Jan and Frits, i wanted to say thank you for all this information you are giving and all these questions you are answering. I read the 10 years of conversation on this forum during covid containment. I spent the night there that I did not see pass and my wife does not thank you lol. I would not like to pollute this discussion with my little engine problems, but I have already seen fried give information to make a cylinder head so I try my luck if by chance he would have his precious time to give me. I have an italian husqvarna 125 in 54.5x54.5 with a flat piston and I drive with commercial gasoline sp98. I would be honored to ride with a cylinder head designed by a 2-stroke monster but in any case, thank you again to you both for this generosity of knowledge sharing[Vous devez être inscrit et connecté pour voir cette image]

Good evening Samy, I think all the replies to your questions about cylinder head design are already in this topic (torispherical shape, squish area percentage, sharpness of the transition between squish area and dome, etc...).

Nombre de messages : 5 Localisation : France Date d'inscription : 21/03/2020

carlovitch1 a écrit:: Good evening Samy, I think all the replies to your questions about cylinder head design are already in this topic (torispherical shape, squish area percentage, sharpness of the transition between squish area and dome, etc...).

Bonjour Carlovitch1, en effet j'ai apprécié toutes ces infos mais au niveau du dôme par contre je ne me rappelle pas avoir lu quelque chose ou alors je n'ai pas compris vu mon niveau d'anglais...

OK, les infos ici: [Vous devez être inscrit et connecté pour voir ce lien]

Et désolé, j'ai écrit une bêtise plus haut la forme du dôme n'est pas torisphérique mais bien toroidale.

Nombre de messages : 5 Localisation : Holland Date d'inscription : 10/05/2014

I love reading all these topics over and over again, still learning of my mistakes on track and testbench. Sometimes having some small successes which makes mee feel great and bringing a lot of joy. Thanks to Jan, Frits and all other members for contributing to this wonderful stuff. aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) - Page 5 241515

aprilia - [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5) - Page 5 241515

Nombre de messages : 5 Localisation : France Date d'inscription : 21/03/2020

carlovitch1 a écrit:: OK, les infos ici: [Vous devez être inscrit et connecté pour voir ce lien]

Et désolé, j'ai écrit une bêtise plus haut la forme du dôme n'est pas torisphérique mais bien toroidale.

Merci pour le lien, j'avais lu ça et c'était très intéressant mais j'ai un piston à dessus plat et la culasse qui va avec. Pour la largeur de la bande de squish ok mais pour la forme du dôme je voudrais pas faire n'importe quoi vu que mon piston est vraiment différent des bombés.
PS: je suis vers Perpignan toi aussi à ce que je comprends.

Si tu te réfères à ce que Jan Thiel explique dans une de ses interventions, la configuration de type "piston plat" n'est malheureusement pas idéale (moins de refroidissement de la calotte du piston et donc risque accru de détonation).
Ceci étant, une adaptation de la forme toroidale préconisée me semble être une option intéressante pour améliorer la combustion.

Nombre de messages : 5 Localisation : France Date d'inscription : 21/03/2020

carlovitch1 a écrit:: Si tu te réfères à ce que Jan Thiel explique dans une de ses interventions, la configuration de type "piston plat" n'est malheureusement pas idéale (moins de refroidissement de la calotte du piston et donc risque accru de détonation).
Ceci étant, une adaptation de la forme toroidale préconisée me semble être une option intéressante pour améliorer la combustion.

Et oui mais je suis en piston plat d'origine et faudrait trouver un piston bombé qui corresponde..... Je joue pas le mondial non plus je voulais faire une meilleure culasse. Je vais prendre une vhm et basta !

Pourquoi ne pas prendre un dôme "plein" à usiner et te faire une extrapolation de la forme préconisée par nos experts, adaptée à ton piston plat? Tu gardes le même volume et le même type de forme et tu ne devrais pas être loin de la vérité.
A ta disposition en MP si tu le juges nécessaire.

Nombre de messages : 106 Localisation : Biblis Date d'inscription : 14/01/2017

Hello,

i´ve got a question to Frits Overmars.
Engine: PVP 252, engine related to RSW 250
Carburetors: Dellorto VHSJ 42mm
Airbox: related to RSW 250(other cylinder angle)
What is your guess for the correct intake length(or volume)?
Valve disc to slider (facing engine side) or open end of the bellmouth.
I´m about to adapt the carburetors to the rotary valve cover and that´s a good opportunity.
Best regards,
Bernd

Toine pour les MP de Samy il lui faut plus de post , vous êtes voisin peut être .

Döllinger a écrit:: i´ve got a question to Frits Overmars. Engine: PVP 252, engine related to RSW 250. Carburetors: Dellorto VHSJ 42mm. Airbox: related to RSW 250(other cylinder angle). What is your guess for the correct intake length(or volume)?
Valve disc to slider (facing engine side) or open end of the bellmouth. I´m about to adapt the carburetors to the rotary valve cover and that´s a good opportunity.

"Engine related to RSW 250" could mean anything Bernd. If your engine is an identical twin of the RSW, you can simply copy the RSW-layout. But if the relationship means a distant cousin, your guess is as good as mine.
Crankcase volume and rotary valve timing can make a lot of difference. Generally speaking, I would go for a short inlet tract and an early-closing inlet disc.

Nombre de messages : 106 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Frits,

crankcase, cylinders (ports), exhaust, are a 1:1 copy.
Differences are the pneumatic 2-step powervalve and the original carburetor. You already gave me the Aprilia inlet timing and the layout for the rotary disc design.
The carburetors are changed to the Aprilia ones and the electric controlled Powervalve is at my To-Do-List.
Best regards,
Bernd
PS. Can you give a link for your picture collection? I´m not abled to find it.

I tried a short inlet tract and early valve closing at Aprilia.
Of course!!! As this always had worked very well....
On all my engines.
But it did NOT work on the Aprilia engine!

Frits Overmars a écrit:: Generally speaking, I would go for a short inlet tract and an early-closing inlet disc.

Jan Thiel a écrit:: I tried a short inlet tract and early valve closing at Aprilia. Of course! As this always had worked very well on all my engines. But it did NOT work on the Aprilia engine!

I am aware of the Aprilia's deviant behavior, but since I had no detailed information about Bernd's engine, I preferred to stay on the safe side with my general advice. A short inlet timing can always be extended a no extra cost if the engine appears to need it, whereas working the other way around could necessitate the manufacture of new inlet discs.

Döllinger a écrit:: Can you give a link for your picture collection? I´m not able to find it.

It was on my Google Drive, but somehow everything got lost, and I haven't yet figured out why.

Nombre de messages : 106 Localisation : Biblis Date d'inscription : 14/01/2017

Hallo,

can you describe what was the problem with a short inlet tract in the RSW? And what was done to solve this?

The measurement for the inlet tract: Rotary disc to slide (rear) surface: 38mm with the Aprilia carburetor and 44mm with the PVP carburetor.
Rotary disc to open end of the carburetor: 90,5mm with the Aprilia carburetor and 96,5mm with the PVP one.
What are your thoughts about that configuration?
And Frits, you are right, to elongate the inlet is no big problem.
Best regards,
Bernd

Nombre de messages : 5 Localisation : France Date d'inscription : 21/03/2020

carlovitch1 a écrit:: Good evening Samy, I think all the replies to your questions about cylinder head design are already in this topic (torispherical shape, squish area percentage, sharpness of the transition between squish area and dome, etc...).

Salut redonne moi ton mail tu as du te tromper !

Nombre de messages : 27 Localisation : lyon Date d'inscription : 19/11/2011

Hello,

I have one question:

Why the piston pin is full?

For less volume in the crankcase? or because when the piston goes down, boost exhaust port and the transfert port A are in relation in a few moments?

Bests regards

Nombre de messages : 362 Localisation : Belgique Date d'inscription : 05/12/2011

MINGRET01 a écrit:: Hello,

I have one question:

Why the piston pin is full?

For less volume in the crankcase? or because when the piston goes down, boost exhaust port and the transfert port A are in relation in a few moments?

Bests regards

this

Obviously NOT for crankcase volume!!!!

Nombre de messages : 27 Localisation : lyon Date d'inscription : 19/11/2011

When I test on the dyno run, I have no difference enter pin full and pin empty!

MINGRET01 a écrit:: Why the piston pin is full? For less volume in the crankcase? or because when the piston goes down, boost exhaust port and the transfert port A are in relation in a few moments?

It is not full; it is hollow, but closed at the ends, in order to minimize leakage between the auxiliary exhaust ports and the A-transfers, like Janbros already indicated above.
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