[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Perra.S a écrit:

Frits, any news on the 50cc low compression engine? How did the test go?

Not too bad. It won.

I've searched through the pages after the ignition curve used for the RSA. I remember to have seen it but can't find it anymore.

Can some one repost it of guide me in the correct direction?

Frits Overmars a écrit:

Perra.S a écrit:

Frits, any news on the 50cc low compression engine? How did the test go?

Not too bad. It won.

Is there a link to a thread or website where we can follow progress and get details? I'm sure I'm not the only one who is extremely curious about the "Adventures of Frits and Friends". :)

~Josh

Areomyst a écrit:

Frits Overmars a écrit:

Perra.S a écrit:

Frits, any news on the 50cc low compression engine? How did the test go?

Not too bad. It won.

Is there a link to a thread or website where we can follow progress and get details?  I'm sure I'm not the only one who is extremely curious about the "Adventures of Frits and Friends".

Here you go, Josh: [Vous devez être inscrit et connecté pour voir ce lien]
No, seriously: developing an engine does not leave us any time for production of an adventure story  .

I couldn't help but laugh.  In my repair shop I do a lot of neat problems that I'd like to share with my friends and on the internet and more.  I take a LOT of photos with intentions of discussing these things with people, but the extra time is hard to find.  That said, I completely understand your position and appreciate your reply. :)

I appreciate your sense of humor Frits, and I appreciate all of the dedication and time you, Jan, and others have spent inspiring and educating guys like me.  I hope that someday I can "pay it forward" when I am wiser and more experienced!  

Kindest Regards,

~Josh

Areomyst a écrit:

I couldn't help but laugh.

Mission accomplished  .

Citation :

I appreciate all of the dedication and time you, Jan, and others have spent inspiring and educating guys like me.
I hope that someday I can "pay it forward" when I am wiser and more experienced! 

That will be tomorrow then; you learn every day.
I have the feeling that ten years ago I knew next to nothing. And ten years from now I will probably feel the same about 2013.

Hallo guys,
we are followers of this forum and never thought we would find a photo of our engine.
We are honored and very pleased of that.
BSG means 3 people who play with 2 stroke as a hobby (not for work). Right now we are having fun with Vespa Piaggio engines.
Always fans of rotating disk  engines that we think highest expression is in Mr Jan Thiel.
The picture here posted is the penultimate version with the old cylinder.
Thanks to passionate suppliers and good friendships we are now able to build all the details of the engine; like casting and cnc machining. But more important, we are independent about the design.
About the costs, Mr. nick gill, as we said, we pay only the machining and/or the row material cause the design is optimized for machines on which things are worked-on.
So, from the outside, could appear a very expensive work, but in fact we didn't spend as it seems.
Race results in 150mts drag are encouraging. Sometimes we have to battle against less power bikes, that are more effective in this tipe of races, but we doesn't matter. It's so beautiful to hear a rotary frontal disc, that it's enough for us.
This year we had our best time in 150 mtrs at 6.3 seconds with top speed of 136km/h. We must use wrist gear change system and can't modify well base (vespa is 1280mm). So you can immagine how is funny...
We had also built a reed valve engine using a TM KZ10 cylinder, and with less development and less hp, we had very similar times with less speed cause it's easyer to start in first 30 mtrs. The TM casing has not removable transmission.
Both engines are 58mm bore and stroke of 56 cause we must stay under 150cc displacement.
All internal components except the cranck-shaft are interchangeable with the original Piaggio, but in our case we have rebuilt them to resist the greater stress.
Both engines are under development; we are devoting ourselves to in the balancing of the cranckshafts, and trying many new exhaust pipes. Also modified cylinders are in work for 2014.
The run-up to reach more hp is continuous.

Fabio, Ale, Stefano
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inside 1
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inside 2
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reed valve TM
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our gears...
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Last rotary engine
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New BSG cylinder
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The first rotary with Pavesi cylinder and original piaggio casings
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Hello guys, welcome on board  
Have you got a YouTube link where I can hear the sound of your rotary valve engine...I have an old Gilera 125 with rotary valve ( engine made  by Jan Witeveen ( spelling ? ), not a good a friend of Frits and Jan  , but it's very special for an old motocross bike.

hurricane a écrit:

Hello guys, welcome on board  
Have you got a YouTube link where I can hear the sound of your rotary valve engine...I have an old Gilera 125 with rotary valve ( engine made  by Jan Witeveen ( spelling ? ), not a good a friend of Frits and Jan  , but it's very special for an old motocross bike.

wow, it's a good bike, it's rare!

here the link to some videos:
trials:  https://www.youtube.com/watch?v=pIbOa2O3x1o

last win in Trecasali PR:  https://www.youtube.com/watch?v=ojVZGddf_AY
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my channel: [Vous devez être inscrit et connecté pour voir ce lien]
et3.it channel: [Vous devez être inscrit et connecté pour voir ce lien]

Wahooo, nice sound  Thanks for the links...
Can I send you my Gilera engine to make it work like yours ?  
Some pics of the engine and the bike. A little out of topic, but not that much..
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hurricane a écrit:

Wahooo, nice sound  Thanks for the links...
Can I send you my Gilera engine to make it work like yours ?  
Some pics of the engine and the bike. A little out of topic, but not that much..
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That's very nice bike Hurricane(as in Bob Hannah I presume  ) but did you know Gilera made a twin? We can only imagine how the GL would have ruined that project.
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I have one little question... Some time ago mr. Theil told that they are use EGT sensor closer as possible to the exhaust port. and my question is what was the ideal exhaust gas temperature and how close to the piston was the EGT sensor? we usualy use EGT about 9-10 cm from piston but temperature depends on the position of sensor (if its on top of exhaust or from the bottom...) we are used AIM EGT senors, but now i wants to try longer temperature sensor which will be in the middle of the exhaust diameter an closer to the piston

Hi Alcatelko

Here you can see how the AIM EGT sensor was mounted on our BRC250cc tandem twin Superkart engines in the exhaust manifold close to the mounting face. In this position we would be looking for a max EGT of around 550 deg C (max 575). If we were mounting in the expansion chamber at about 150mm from the piston face we would be looking for 650 deg C (max 670). In both cases just the thin tip of the AIM sensor extending into the exhaust
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Best Regards

Ian

thanks very much...when we mounts EGT about 90mm from piston on my exhaust was temperature between 350-400°C but on other scooter when was sensor on other side of exhaust was temperature about 550°C with ideal tuned air-fuel ratio (both exhaust were isolated by thermotec for about 30cm from cylinder)

now I have self made exhaust and I want mount EGT as good as possible:happy: 

alcatelko a écrit:

Some time ago mr. Theil told that they are use EGT sensor closer as possible to the exhaust port.

Mounting an EGT sensor close to the cylinder is not the best way to register exhaust gas temperatures because washed-through fresh mixture will cool it down under certain circumstances. The Aprilia sensors were fitted in the exhaust flange nevertheless because sensors fitted further downstream suffered too much from vibration.

So where is the best location for the sensor? I want to do it as the appended drawings so that the sensor will be in the middle...
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sorry for ugly drawing :-)

Ian Harrison a écrit:

Hi Alcatelko

Here you can see how the AIM EGT sensor was mounted on our BRC250cc tandem twin Superkart engines in the exhaust manifold close to the mounting face. In this position we would be looking for a max EGT of around 550 deg C (max 575). If we were mounting in the expansion chamber at about 150mm from the piston face we would be looking for 650 deg C (max 670). In both cases just the thin tip of the AIM sensor extending into the exhaust
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Best Regards

Ian

When the end of season "everything must go sale" ? 

alcetelko I don't think the orientation makes as big a difference as the distance from the piston

Institute of TwoStrokes a écrit:

When the end of season "everything must go sale" ? 

Everything went already. After we finished racing in the CIK/FIA European Superkart Championship all our BRC engines were sold to Australian customers

Frits is 100% correct regarding vibration damage to the EGT sensors. We are lucky to get 1 meeting out of the AIM sensors mounted in the exhaust of our 250 singles.

Best Regards

Ian

Daniel A. a écrit:

Hello,

Is there a good source to get (new) carbs with inclined fuel chamber from? I am looking for one with 34-38mm in diameter. I've already looked at Mikuni, Dellorto and Keihin. Without success.

I know that Aprilia RS 250 and Suzuki RGV 250 have got 34mm Mikuni(?) carbs with inclined chambers, but I'm not sure if these relatively old carbs are well to adjust

Regards,
Daniel

Maybe the Keihin FCR's, can can work pretty well in 2 stroke engines as far as the internet says.
And that Gilera cylinder looks exactly like the HuVo cylinders that where made for the Casal 80 racing engines, almost all racing cylinders from that era are very similar :o

Institute of TwoStrokes a écrit:

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I would love to know more about this Suzuki GP100/125?

I have a questio for Mr. Jan.
Have you ever tried to offset the piston pin during RSA engine development?
And, if you tried what was the result?

luca.lorigiola a écrit:

I have a questio for Mr. Jan.
Have you ever tried to offset the piston pin during RSA engine development?
And, if you tried what was the result?

We used the same piston as the RSW.
This piston had the piston pin offset 1mm in the direction of the exhaust port.

TZ350 a écrit:

Institute of TwoStrokes a écrit:

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I would love to know more about this Suzuki GP100/125?

One would think your all "GP'd" out by now Rob  

hi

has anyone a diagram how the powerjet is programmed for the 42 VHTC carburetor in the RSA?


thanks Manuel

Manuel Rainer a écrit:

hi

has anyone a diagram how the powerjet is programmed for the 42 VHTC carburetor in the RSA?


thanks Manuel

I do not have any diagrams Manuel.
The powerjet was closed until about 10.000 rpm.
In was open until 12.500 rpm
After 12.500 it was gradually closed.
a powerjet of 120 was used in combination with a main jet of about 220.
On track the carburation has to be richer, because of the rising airbox pressure.
So you need a different diagram for each gear!