[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)

Institute of TwoStrokes a écrit:

Frits are there any studies conducted to find out if the reed petals(clappets for Jarno) completely close when the engine is in phase?

There must be hundreds of such studies; just look at the list of SAE-papers. And in case you really want to know, it's not too difficult to do it yourself. Make an appropriate window and run the engine with a stroboscope for which you can move the phase, while leaving its flashing frequency governed by the ignition. That way you can scan all crankshaft positions in the running engine.

Un "aimable informateur" m'a fait parvenir ce document rarissime sur lequel apparaît notre ami Jan Thiel!

Qu'il en soit remercié!



PS: je vais modifier le smiley en conséquence...

En voyant cette photo de Jan THIEL la lime à la main,

je ne peux m' empècher de penser à cà : [Vous devez être inscrit et connecté pour voir cette image]

(cylindre Solex 6 transferts de Solexgump)

Le sens de l' humour de Maître Jan et de Marc me pardonneront ce

elles sont minuscules ?
Aurais-tu moyen d'augmenter la résolution de l'image ?

Lolo, tu nous fais ds la pornographie a nous montrer les dessous d'une dame comme çà.



superbe tes photos.

Hi everyone , this is the best two stroke topic on internet with serious fans and professional engineers involved.
It is sad that some motorcycle corporations are killing two strokes even in prototype racing where the most important are performance and competition.
Lets keep two strokes and this topic alive with great pictures, discussion and ideas

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Hi

Sorry for my english

I’m Stefano…
I’m working on the development minibike engine.
These bikes do not have the change ... have a similar range of use for karting 100

I'd like to build a plug to the jack that replaces Seeger

What do you think?

[img][Vous devez être inscrit et connecté pour voir cette image][/img]

Così, Stefano ?
left = original Aprilia RSA closed piston pin + clip; right = FOS piston plug.
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Frits Overmars a écrit:

Così, Stefano ?
left = original Aprilia RSA closed piston pin + clip; right = FOS piston plug.
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Hi

I have seen these photo in previous page... but this solution is in "plastic"....special plastic...
I would like this piston plug in metal... "press mold" in sostitute of the seeger.

Marc a écrit:

Un "aimable informateur" m'a fait parvenir ce document rarissime sur lequel apparaît notre ami Jan Thiel!

Qu'il en soit remercié!



PS: je vais modifier le smiley en conséquence...

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

Voilà ce que j'aime avant tout



Même si je ne lis presque rien pas tout (car je suis vraiment trop nul en English speaking et pire en reading



Néanmoins, je suis et je reste béat d'admiration face à Jan Thiel et Frits Overmars

+1
Incapable comme toi de bien comprendre l'Anglais et du coup très frustré ... Snif !

Hi two stroke fans. This thread is very interesting especially 24/7 idea from Frits, so I was testing some reed valve modifications on Gilera Runner 180 scooter to get better flow and the results are promising.

There are two types, first is reed valve without any barriers and with completely closed carbon petals.
This version could be good for bikes with gears and it is working good on my scooters too.
The only problem is that reeds have "classic" tension for closing and because of absence of upper bridge where they sit they are prone to brake after about 30 minutes of race track operation.
After testing I found reed life is longer if the reeds are more loose to the side walls.

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To get even better mixture flow and longer reed life, I made different sidewalls angle which doesnt sit reeds on sidewalls hard as standard reed valves, and in "natural condition"(bad english) on the upper side, free play to side walls is becoming of about 1.5 mm. I think this is improving reed life because they
are not hitting very hard on side walls in high rpm , and for lower rpm they are still closing to prevent losing pressure in crankcase.

Between reeds I also made opened space of 2 mm when they are siting(closed) on sidewalls. With this opened area I wanted to get even bigger opening at high revs.
There are no problems with starting cold scooter and start is very good. I dont have dyno to make test but I can feel that engine is stronger in powerband.

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I don't know if this is the right place to discuss this, since this has nothing to do with RSA.
however i have been using a similar thing last year, here it is.
I have seen this design previously on an old kart engine, don't remember which one really.
Sorry for my name on two images.

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straight aluminium is good because i was using methanol, viton coatings are not the way to go with methanol.
the valve flows a bit better than an usual one and on this design the reeds are touching each other (the tip has to be grinded properly for contact)
reeds last about one third than with coating, it is even possible to make the reed bounce on the reed cage surface at the frequency of the engine, thus having a higher power output but (really) reduced reed life.

stiffer reeds last much longer because of reduced bounce on the cage (more reed inertia and less tip lift). Improved reed life (and i think performance too) can be achieved by mirror polishing the contact surface.

with a gap between reed tips like your design I found problems with carburation at low and mid rpms. the engine is usable but i think an asolutely clean carburation improves your feeling of the bike. so the gap on my design is so small the reeds are actually touching each other.
Cheers
Stephan

Hi Stephan, i am using "open" design which is better for my engine configuration and for reed life also because it has distance on the upper side between reed and the cage, and when they are at certain rpms hitting on the cage it is easier for them.
Now I am making the same open design, and the reeds when they are laying on the cage will be completely closed to help reducing back flow.

On my closed reed valve like you are using the gap is very small as yours but the reeds are not tight on cage because when I tested it with tight setup as on normal reed valves, they were snapping earlier. It looks like my engine doesnt need tight closing reeds.

Cheers
Stipe

Small update, in last testing I made open version with gap between top of the reeds of 15 mm in default position to get even bigger opening and easier reed hitting on the cage when it is closing.

Conclusion: the engine is working very good in mid and high rpms and it could easily take bigger carb also(now is 28), but the problem are reed life. Even if they have 15 mm gap at top and circular and smooth cage area they are still closing(hitting on cage) which I can see from cage marks on reeds. Reeds are thin(0,30) and with that hitting they start small shredding on top of them, thicker reeds could reduce this problem.

Cheers

nasone32 a écrit:

reeds last about one third than with coating, it is even possible to make the reed bounce on the reed cage surface at the frequency of the engine, thus having a higher power output but (really) reduced reed life.

stiffer reeds last much longer because of reduced bounce on the cage (more reed inertia and less tip lift). Improved reed life (and i think performance too) can be achieved by mirror polishing the contact surface.

After some more testing with opened reed design(12 mm gap) and this this time with viton coating on the cage, reeds(0.30) start shredding in the middle top area so thicker reeds will be of some help.

It looks that reeds in high rpm are vibrating and bouncing (like guitar string) with this setup, and for longer reed life they need steadier closing like on normal reed valve.
For next test I will make opened reed design with viton coating and with center bridge to see if it will help
"vibrating reed" for longer life and also test with thicker reeds.

After all this reed-mess it could be much better to start working on real 24/7 system :)

SB07 a écrit:

Hi

Sorry for my english

I’m Stefano…
I’m working on the development minibike engine.
These bikes do not have the change ... have a similar range of use for karting 100

I'd like to build a plug to the jack that replaces Seeger

What do you think?

[img][Vous devez être inscrit et connecté pour voir cette image][/img]

Unfortunately no match for the resources at industrial power house Institute of TwoStrokes. :lol: :lol: :lol:
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(for Jarno)
Malheureusement, aucun match pour les ressources à puissance industrielle chambre de l'Institut de 2T

Hey Lozza , Devcon Ti

My opinion is:

[img][Vous devez être inscrit et connecté pour voir cette image][/img]

Frits Overmars a écrit:

Avoiding short-circuiting between transfer and exhaust ports is the most obvious goal of the plugs. But it is not the only one. Do you remember Honda's TRAC system where at low revs a resonator volume was coupled to the exhaust duct to lower the exhaust system's Helmholtz frequency (Suzuki and Kawasaki used similar systems)?
The volume inside a piston pin does more or less the same: during every revolution it is momentarily connected to the auxiliary exhaust ducts and it dampens the system's resonance, even if you don't want it to, i.e. when the engine is running in the power band.

Your close Seb I can make them domed. :)

Merci Jarno Je suis incapable de contrôler moi-même où les traductions en ligne sont concernés

Votre étroite seb je peut les rendre Bombé . :)

Hi everybody

I am Romeu, I am Portuguese and I am 21 years old.

Learned good things by reading this topic twice. Thanks to everyone, specially Frits and Jan Thiel.

Now, with this information I have the conclusion that I am doing some mistakes tunning my engines.

I have tuned a couple of 2 stroke engines.

My tuned bike is a Honda NS1-80cc or just NSR75cc, it have a Honda CRM 125 engine on it, with NS1 electric system (cdi and cables) adapted, tuned cylinder, tuned head for around 13:1 compression ration, using a YZ 125 97-01 piston, mikuni tm 35, and hand made exhaust made for maximum power around 11750 rpm....

I have some problems with low rpm power when exhaust return is undesirable, by about 6000/7000 rpm because I still have the exhaust valve voluntarily stuck fully open. Meanwhile, I buyed a Honda RS 125 NF4 cylinder and NX4 E-2 Head with 10.6cc of volume or so at a very good price and excellent condition. It fits with few modifications on the CRM 125 engine, when my original cylinder gets tired, I will replace it with the rs125 cylinder.

My idea is to get a good 38/39mm carburettor and a 110mm center to center KTM 125 conrod and fit it on the CRM 125 crank for improvements in leverage, lower crank compression a bit and the other advantages on a bigger conrod like less suffering from acceleration.

One of my doubts is the exhaust I will have to build to fit the cylinder and my frame et cetera, the Objective is drag races, 600/800 meters, sometimes 1 kilometre or more.

I don't know exacly how much length and diameters it should have, so I am thinking about this:

Header diameter of the RS125 is 40mm right!?
Total lenght maybe about 820mm or 830mm;
Mid section about 115/120mm in diameter;
Stinguer size about 22mm of diameter.

Can you people provide me with some sizes of real Honda RS 125 exhaust sizes?

Sorry for my bad English.
Thanks alot.
Regards

I have repplies for all your questions BUT

I do believe it's not the place to do that , you first need to do a "presentation" write up

then post in the technical section but sorry your answer have nothing related to RSA engines , if so , i couldn't repply