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

It looks like the koenig engine (1967), except the disk transmission witch is drived by a toothed belt.

Kreidler a la Koenig:
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This project on an upside down tilted Kreidler engine was made by me only as an engineering exercise on a 25 Euro lathe in the shed of my parents house in The Hague. In fact I'm probably the spiritual father of the König in road racing . My article in 1967 in the Dutch MOTORSPORT magazine was the start. Most important however was my idea to use a toothed chain as primary drive as all roller chains costed lots of losses when hot. Kim Newcombe who was a very good mate of me in those years used the ideas, by that time I worked for FOKKER aircraft in Hamburg as Technical Representative. I also penned a simple water brake for him to test as Dieter König thought this was not necessary. Kiwi Tim Hannah did not have the gocking futs to mention my role in the history when writing the Newcombe-König story. When I ever meet him I'll give him a workover he will never forget. Unfortunately I dont have so much time anymore as I got metastasis of prostate cancer in the lymf glands and bones. Nowadays I'm still active with crankshaft balancing with bobweightds from 50 till 26000 grams, maybe a record? Furthermore my best friend and scientist PETER VAN LEEUWEN and me have developed an absolute unique cdi with higher efficiency than any other system we tested so far for twostrokes. Being 76 does not prevent me from marching along, Old Bastards Never Die. Period.

This is very interesting, thank you Bob.

As far as I understand you claim that the idea to use this disc valve's drive came from your previously test on a Kreidler engine in 1967 ?

For various reasons I have been searching a lot about Konig's history and finally came to the conclusion that Dieter Konig may have taken some good ideas from others people, for example the use of rotary discs valves on its outboards engines, I would like to know when did he exactly use such a system but actually I would say since 1957/58.

Also I would like to know when did Dieter use for the first time an expansion chamber system on its outboard's engines.

There is a very good and complete topic about Konig's history an "Boat Racing facts" forum but as you can imagine it's mainly about outboards history.

Any more informations about these technicals details you could provide will be very helpful for me.

Meantime please excuse my bad English.

Dieter was not aware of the fact that the disc on top of the crankcase was a JAWA patent. MZ also had already such a system but the drive system failed. Dieter complained to me when he was visited by a lawyer on behalf of Jawa. I was very impressed by the disc on top system that I had a go on the pictured Kreidler that went to VAN VEEN but was blocked by HENDRIK VAN VEEN who cheated me when he hired me to lead the racing department but never made his promise come true. That's life,shit happens and bastards are everywhere and all around us all the time.

As far as I can remember Jawa didn't use a disc valve on top of the crankcase but only behind the cylinders (see patent dated 6 April 1960) but if you can prove me the contrary with a picture of a Jawa engine using such a system I will be glad.

About MZ yes you are right, Kaaden did experiment such a system in the late fifties but it was a failure and no more developped.

Jawa did never made it but it was written in their patent application. They had a very smart brain tank overthere.
I have a lot of respect for Czech engineering since my study time at the Anthony Fokker School for aircraft maintenance engineering in The Hague, Holland.

To be honest I have been searching too about the possibles connexions between Jawa and East Germany two strokes's production in general (mainly because of the geographical situation) but could not prove anything at the moment on this particular subjet :
Could the idea of a single rotary disc valve feeding two cylinders used and patented by Jawa could came from East Germany ?

In my opnion this is the famous ROTAX solution, under supervision of the legandary Chief Development engineer Professor Dr Ing HEINZ LIPPTSCH whom I regard as my best teacher. He was also a very good 125 road racer and was several times Austrian champion on a self prepared Rotax.

I know that Rotax used this system on its" type 451" engine but I don't know the year exactly, I would say about 1980.

Then I found the Jawa's patent dated 6 April 1960 and using the same system, this is 20 years before Rotax. I have some informations from my own researches showing that this solution could date from an East German engine build in 1950.

What I would like to know/prove is that this idea patented by Jawa in 1960 could came from my 1950 East German engine, this is an extremely hard job as you can guess..

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Thank you so much for your excellent research!

There is no need to thanks me it is only for my "pleasure" but I must admitt that I would be happy to see this Jawa patent of a rotary disc valve on top of the crankcase.

This is new information to me. Do you know the exact date of that patent ?

I also wonder when did Jawa use a rotary disc valve for the very first time on their racing bikes ; I would say during the sixties.(Maybe on the famous Jawa 350 V4 ?)

The JAWA brain tank in the Czechoslovakian Republic tried to maintain the high technial standard for which they were and are famous. Due to the Russion occupation they could not make what the designed and tried to sell some patents. Not all Eastblock patents could be sold. Dieter König had to pay fees for viaolating Jawa rights and I was blamed for the publication of the idea using the flat four in road racing. It was clear that Dieter had not done his homework.
Another sad story is the complete demolishing of ALL SKODA sportscars in 1968 after the Prague spring including spares, tools, drawings and parts by the designers, engineers and mechanics under armed supervision of Russian bastards. Skoda was in fact the first one that built a fantastic 2 litre 16 engine long before Cosworth did. It used 50mm sand cast Weber DCOE carbs. When LEO HNATEVIC who penned these cars told me about it in 1986 he cried about it.
Hoowever the Czech mind was so strong that they never gave up. Skoda bought thru my work as middleman a Superflow 901 test bench and a big flow bench in 1986 but Neil Williams of Superflow refused to pay my fee.So you can see there are also bastards in the USA. Then and now!

Really , really really interesting ! Many thanks

I've suspected Jawa to be ahead of its time and I am still trying to learn more about this Company actually but I didn't know about this Skoda  racing car's 2 liters 16 valves's engine "before Cosworth". Interesting.

You may think that Konig was the first thanks to you to use a flat four two stroke engine for road racing but please do not forget that Englishman Dennis Jones did the same during the forties. In addition it was a supercharged engine.

I have a question for Frits regarding the old reliable Mikuni VM 34 carburetor. There are two types of needle jets available, the 159 and the 176 (bleeder type) series. My question is have you had any experience using the 176 series on reed valve or rotary valve motors? Is there any advantage to using the bleed type over the standard type? What effect on mixture would going to a bleed type tube have. Would you need to go to a richer tube? For example would a 159 P4 need a 176 P6.
I have never used a 176 series but i am always looking for improvements.
Thanks, HG

I'm in favour for the bleed type as it creates earlier and better emulsion. If you combine this with a longer needle jet outlet the carb will be more responsive in the lower and midrange. After all the longer the needle jet outlet the higher speed and thus a lower pressure will be encountered.
If I were you I would go for the modification of making a Main Jet Needle set up like Yoshimura has i.
Have a good look at i
I think it's the best thing that has happened to carbs in ages. Just google for it.

PS Howard I can make you such a holed needle.

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Good job VS!

lvs a écrit:

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hello

what i can see on this page this carburetors are used in 4T engines.
does this system also has a benefit on 2T engines. fore example on a rotary valve racing engine?

thanks
Manuel

2 more interesting pictures :

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from july 1981, Cagiva 500
seems odd to me that they didn't place the holes in the middle of each crankcase


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from october 1981 Jawa 250. instead of a disc, an up and down moving valve. advantage over piston controled is that you can offset the opening from BDC.
but that can be achieved with a disc to, it is more complicated (heavier conrod or is it conrods ? , harder to balance ?) AND the port is fuly open only for a very brief moment, no wonder it wasn't a succes.

FWIW, somewhat updated versions of 4-cylinder Konigs are in current manufacture.

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Hey!

My name is Eugen, I am from Slovakia, I am 24years old,
I am fairly new in 2stroke tuning.

This is my first post here because I wanted to read the whole thread first.
There is some extremely valuable information shared here!

I would like to discuss something that was mentioned only once here but never really discussed thru.
Its the Y.E.I.S. yamaha energy induction system or "boost system"

I would like to ask if there are working rules of thumb for its volume, shape etc.?
I did a research but there is very little realible info available,

This is maybe the most valuable info I managed to find about it with some rules and comparison of displacement vs yeis volume from road bikes.

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I also have my own idea of a boost system and I hope Frits or Jan or someone really experienced could have something to say to it.

seeing this post of letting air into the transfer ports I got the idea what if I could pre-fill the transfer ports with charge from the YEIS before their opening? It could be a nice low temperature charge that doesnt need to pass thru the crank case.

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Jenco a écrit:

My name is Eugen, I am from Slovakia, I am 24years old, I am fairly new in 2stroke tuning. This is my first post here because I wanted to read the whole thread first. There is some extremely valuable information shared here!
I would like to discuss something that was mentioned only once here but never really discussed thru. Its the Y.E.I.S. yamaha energy induction system or "boost system". I would like to ask if there are working rules of thumb for its volume, shape etc.? I did a research but there is very little realible info available.

Vitajte Eugen,
The primary purpose of the buffer volume used in the Yamaha Energy Induction System was to achieve a more constant flow velocity through the carburettor, helping mixture control. As an additional advantage, engines with a relatively small carburettor would produce a little more power with this system. On engines with a big carburettor the value of YEIS is negligible.
Rules of thumb: buffer volume about twice the cylinder volume, connecting hose diameter about 0,7 times the carburettor diameter. You can then establish the optimum hose length experimentally; all you'll need is a pair of scissors.
The hose should be connected as close as possible to the reed valve and it should be connected to the lowest point of the buffder volume in order do avoid the formation of a fuel puddle in the buffer volume.

Citation :

seeing this post of letting air into the transfer ports I got the idea what if I  could pre-fill the transfer ports with charge from the YEIS before  their opening? It could be a nice low temperature charge that doesnt need to pass thru the crankcase.

Connecting the buffer volume directly to the transfer ducts can be done, but I'm afraid you will not achieve much flow because the average pressure in the buffer volume is probably below atmospheric and the additional reed valves in your drawing will create extra flow resistance.

A practical tip: unless I'm mistaken you made that drawing using MS-Paint. So do I sometimes, and whenever possible I only draw one half of the intended drawing and then I use the Mirror-function to copy and paste the second half. That way I achieve perfect symmetry in half the time .