ESE's works engine tuner

[husaberg]

Frits. How's that inner radius below the case deck work?
New yz85 is like this. I didn't know what to think about it.

Hi i am confused Nearly every case i have seen short of a 1960 old villers/ greeves is radius below the casedeck?

[Vannik]

Hi i am confused Nearly every case i have seen short of a 1960 old villers/ greeves is radius below the casedeck?

Interesting - I saw the inner radius of the transfer port as the radius on the sleeve side of the port?

[husaberg]

Interesting - I saw the inner radius of the transfer port as the radius on the sleeve side of the port?

oh i get it (only after he actually looks at Frits pic again)

Still fairly common




cagiva


YZR500


NSR500


Cant remember what this one was later oh KR3




NSR or RS cant recalll


when we were sharpening septums to razor shapeness that inner area got a radius as well
Just like we were taught from looking at pictures in robinsons, book the sharp point kept them cool at Mach 3

i cant remember where i seen it but there is an odd looking bump in the unmentionable RSW500.

[Frits Overmars]

Frits. How's that inner radius below the case deck work?
New yz85 is like this. I didn't know what to think about it.

I'm not sure I understand your question. Do you mean the radius indicated in the picture below?

[husaberg]

I'm not sure I understand your question. Do you mean the radius indicated in the picture below?

Yes i think he means this bit Frits with the inner radus continues lower than the machined deck height of the cylinder. (Thanks for correcting me Neels)

Now i am going to spend an hour looking for that the weird looking protrusion on a RSW500.

okay 27 minutes
Any ideas re the shapes of this
It looks nothing like any of the other Aprila or Rotax tranfers in design
it almost looks like a different guy did designed the inner side than the outer sider?

Was it just as they tried to use the skinny 250 case?

[sniemisto]

While were at it, I’m curious about this double radius:

What is the reason for “step” and radius change at case deck?

[Frits Overmars]

Now i am going to spend an hour looking for that the weird looking protrusion on a RSW500. okay 27 minutes
It looks nothing like any of the other Aprilia or Rotax transfers in design. it almost looks like a different guy did designed the inner side than the outer side? Was it just as they tried to use the skinny 250 case?

You're spot-on about a 'different guy' Husa.
The RSW500 was the brainchild of Aprilia's then-technical director Jan Witteveen. It was an extremely-short stroke engine and Jan Thiel did not want anything to do with it.

[Frits Overmars]

While were at it, I’m curious about this double radius:

What is the reason for “step” and radius change at case deck?

This was a case of mutilating a new cylinder design because it had to fit old-type crankcases. You also see it quite a lot on aftermarket big-bore cylinders.

[tdc211]

Piston at bdc. ktm cylinder next to it

[jamathi]

This was a case of mutilating a new cylinder design because it had to fit old-type crankcases. You also see it quite a lot on aftermarket big-bore cylinders.

This is particularly bad...
This is the main cause why big-bore cylinders usually give diappointing power....
The transfers become too small!!

[jamathi]

I'm not sure I understand your question. Do you mean the radius indicated in the picture below?

This radius gave about 0.4HP more...

[jamathi]

Yes i think he means this bit Frits with the inner radus continues lower than the machined deck height of the cylinder. (Thanks for correcting me Neels)

Now i am going to spend an hour looking for that the weird looking protrusion on a RSW500.

okay 27 minutes
Any ideas re the shapes of this
It looks nothing like any of the other Aprila or Rotax tranfers in design
it almost looks like a different guy did designed the inner side than the outer sider?

Was it just as they tried to use the skinny 250 case?

This engine was a complete failure, best power was, of course, reached when it was finally enlarged to 500cc....
I still don't understand why they needed 5 years to discover it....................
It just shows how little they understood about engines!

[jamathi]

You're spot-on about a 'different guy' Husa.
The RSW500 was the brainchild of Aprilia's then-technical director Jan Witteveen. It was an extremely-short stroke engine and Jan Thiel did not want anything to do with it.

Enlarging a 250cc engine proved to be a totally wrong idea....
Of course the short stroke engine was always short of power.
And when it was finally enlarged to 500cc the gearbox broke....
Small wonder, as it was basically made for a 125
The 250cc tandem used already the 125 gearbox, sometimes broke..
I still think a well-made 500/2 could have won!!!!

[husaberg]

You're spot-on about a 'different guy' Husa.
The RSW500 was the brainchild of Aprilia's then-technical director Jan Witteveen. It was an extremely-short stroke engine and Jan Thiel did not want anything to do with it.

Enlarging a 250cc engine proved to be a totally wrong idea....
Of course the short stroke engine was always short of power.
And when it was finally enlarged to 500cc the gearbox broke....
Small wonder, as it was basically made for a 125
The 250cc tandem used already the 125 gearbox, sometimes broke..
I still think a well-made 500/2 could have won!!!!

Cheers Frits and Jan

---

https://www.honda.co.uk/engineroom/w...the-honda-nsr/

I read this today on Hondas own page
Now i never worked at HRC
But i do know the RS500 never had two cranks or Disc valves.


Nor did the Switch to unleaded make it needed to be switch back to 180 crank.

One often over looked advantages of the 3 was it had a lot f room for wide swept transfers as well as full width cadges as did the Single cranked NSR500.
Of course the Tandem and the cranked tandem Aprilia had this room as well.


I seems Honda has forgotten.

[F5 Dave]

Always thought a 500VTwin would make a cracking roadbike in the 90s. . . . If only someone made one. . . .