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

Döllinger a écrit:: With the Keihin ON/OFF solenoids: With the 13Hz Signal you managed to only slightly open the valve so you had a comparable effect to the stepper motors?

The stepper motor that was used before the Keihin solenoid, rotated a threaded needle; its aperture varied analogously with the amount that the needle was screwed towards its seat.
The Keihin solenoid cannot 'slightly open'; it is either completely open or completely closed. Its flow rate varies with the ratio between open-time and closed-time slices, depending on the block-shape of the Pulse Width Modulation signal.

Nombre de messages : 17 Localisation : Belgium Date d'inscription : 29/10/2012

Frits Overmars a écrit:

Döllinger a écrit:: With the Keihin ON/OFF solenoids: With the 13Hz Signal you managed to only slightly open the valve so you had a comparable effect to the stepper motors?

The stepper motor that was used before the Keihin solenoid, rotated a threaded needle; its aperture varied analogously with the amount that the needle was screwed towards its seat.
The Keihin solenoid cannot 'slightly open'; it is either completely open or completely closed. Its flow rate varies with the ratio between open-time and closed-time slices, depending on the block-shape of the Pulse Width Modulation signal.

This posting from 2012 on the other forum just about sums it up. [Vous devez être inscrit et connecté pour voir ce lien]

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hallo Frits,
thank you very much for your answer! A pulsed trigger signal seems doable for me as against a valve with a stepper.
Now i found another solenoid from Kawasaki which is still availabe via normal order. I will compare the Yamaha one to it and take the better one.
Another question: Honda says for the RS 125 that the powerjet is always open under 4000rpm. Above 4000rpm it´s closed if the throttle position is beneath 75%.
Are that values you would recommend as a starting point?
Best regards,

Bernd

Good afternoon all,

While we are talking about powerjets, what do you think about non-electronic powerjets? Do they still bring some advantage over a classical system without powerjet, or are they only gadjets ? I ask this question because I read alot of threads on 50cc and scooter forums where people say that they got rid of the powerjet because of setting issues...
I have one on a 125cc TSR Suzuki that I frequently use for Supermotard practice on pavement tracks and would like to know whether it can help with some fine-tuning.

Döllinger a écrit:: Honda says for the RS 125 that the powerjet is always open under 4000rpm. Above 4000rpm it´s closed if the throttle position is beneath 75%.

This sounds rather surprising to me. It would almost suggest that they are using a wrong needle....

carlovitch1 a écrit:: what do you think about non-electronic powerjets? Do they still bring some advantage over a classical system without powerjet, or are they only gadjets ? I ask this question because I read alot of threads on 50cc and scooter forums where people say that they got rid of the powerjet because of setting issues...
I have one on a 125cc TSR Suzuki that I frequently use for Supermotard practice on pavement tracks and would like to know whether it can help with some fine-tuning.

Non-electronic powerjets were initially introduced to improve the carburation on engines with piston-port inlet systems.
They enriched rather than weakened the mixture at high revs; quite the opposite of what today's electronically-controlled powerjets do. I don't think those uncontrolled powerjets will be of much use on reed valve engines.
I read all kinds of remarks on various forums, from very clever to completely insane. It would be nice if everyone would support their claims with an extensive engine specification and a measured power curve.

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Frits,

This sounds rather surprising to me. It would almost suggest that they are using a wrong needle.... a écrit:

I read that in the >2001 Honda RS 125 manual.

So what would you advice? Not to take a throttle signal at all or would you use the throttle signal in a different way than Honda?
Best regards,
Bernd

Döllinger a écrit:: Hi Frits, I read that in the >2001 Honda RS 125 manual. So what would you advice? Not to take a throttle signal at all or would you use the throttle signal in a different way than Honda?

I do not know precisely what Honda did on their >2001 RS 125, so I'd rather not guess. But if a throttle signal is available, I would definitely use it as an input for the ignition system.

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Frits,

yes indeed that is exactly what i`m going to do. I thought of a kind of "wire-snail" to get a rotating out of the cable stroke. Only a bit hard to built. I never saw one for sale.
A lever system is easier to make but too bulky.
Best regards,
Bernd

Thanks Frits for your quick and precise answer !
I will then not worry that much with mine, because of course the engine is with reeds. Eventually, I will try without it.

Döllinger a écrit:: Hi Frits, yes indeed that is exactly what i`m going to do. I thought of a kind of "wire-snail" to get a rotating out of the cable stroke. Only a bit hard to built. I never saw one for sale.

You might try [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] . They do have the cable-potentiometer for sale, but it's not in their webshops, so you may need to phone or mail them about it.

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Frits,

thank you for the Link. 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 31 771973

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 31 771973

That´s exactely what i was searching for. SMU is offering a 2-cable version up to 47mm slide stroke for under 200€.
That´s a good deal i think.
Meanwhile my Kawasaki-solenoids arrived today. They seem to be made with quality and work with 12V.
[Vous devez être inscrit et connecté pour voir cette image]

Best regards,
Bernd

Nombre de messages : 86 Localisation : Australia Date d'inscription : 05/05/2012

Döllinger would you share the Kawasaki part number for the power jet solenoid

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Of course,
the Kawasaki part number is: 21188-1005
They are 61€ each.
Best regards,
Bernd

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

@Francis:
Regarding your drawing:

On your picture i see that the red tip of the needle is closing the diffusor-bore and not on the valve seat.
So the valve seat is only used as a guide?
Am i guessing right?
I got the parts you posted and will start to modify them soon.
Best regards,
Bernd

You're absolutely right, the sealing is made on the diffuser, the needle body is just a guide.
And it also allows the fuel supply.
I could send you the drawings of the other parts but they are specific to our carburetor.
If I had to start the same project again today, I would use a real injector, piloted like an injector.
We find now small calculators at a reasonable price that have all the essential functions ...

About the throttle position encoder, contacts Riley Will from BRC Engineering Ltd. with a private message, He makes a beautiful device

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hallo Francis,

thank you for your information. I was not 100% sure.
I will contact Mr. Will.
Best regards,
Bern

Here below are the different drawings that could help you:
[Vous devez être inscrit et connecté pour voir cette image]

One more:
[Vous devez être inscrit et connecté pour voir cette image]

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Francis,

really great support! thank you for your drawings. It will be no problem for me to modify the parts like that.

But one question came in my mind: Why do you, or Dellorto, work with an additional float valve, when you eliminate the sealing surface?
Wouldn't it be easier to seal up withthe tip of the solenoid-rod? Are there aligning problems between the difusor bore and the rod tip?
What is the reason for that?
Best regards,
Bernd

On the Dellorto carburetor, the solenoid seals directly on the diffuser.
We chose this arrangement because we had to guide the needle when using the bellow solution. 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 31 584741

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 31 584741

My mistake, there are two intermediate parts in the Dellorto
[Vous devez être inscrit et connecté pour voir cette image]

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Francis,

thanks for your info!

Here a photo of my solenoid with the needle. First small progress. Next week i will prepare the seat ect.
[Vous devez être inscrit et connecté pour voir cette image]
@ Frits or Francis

What diameter of the bores between the jet and the difusor you advice? You told the volume should not be too much. I thought of a diamter of 1,4mm for all sections behind the jet up to the modified needle seat.

Best regards,
Bernd

In our carburettor the diameter of the feed hole is 2 mm.
But I think 1.5 mm should be enough

Nombre de messages : 86 Localisation : Australia Date d'inscription : 05/05/2012

Hello everyone
Frits if you have the time I’d appreciate a clarification
In Pt 2 8-12-12 you wrote of sinking of the top & bottom edges of the ports from zero at the corners to maybe 0.1mm in the middle depending on the port widths while still maintaining sharp edges
The sinking will spare the piston ring while the sharp top edges will hinder flow from the cylinder into the transfers.
Would you please explain what is actually being sunken ?
I assume it is the bore itself, it maybe the floor & ceiling of the ports also.
Thanks in advance

RAW a écrit:: Frits if you have the time I’d appreciate a clarification
In Pt 2 8-12-12 you wrote of sinking of the top & bottom edges of the ports from zero at the corners to maybe 0.1mm in the middle depending on the port widths while still maintaining sharp edges. The sinking will spare the piston ring while the sharp top edges will hinder flow from the cylinder into the transfers.
Would you please explain what is actually being sunken ? I assume it is the bore itself, it maybe the floor & ceiling of the ports also.

I appreciate your concern about my time Raw. But you could do even better, by posting a direct link to the post you were referring to, like this:
[Vous devez être inscrit et connecté pour voir ce lien]

Only the spharp edges of the port windows should be moved back a little, like so:
[Vous devez être inscrit et connecté pour voir cette image]

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