ESE's works engine tuner

[Frits Overmars]

Hello Frits,Thank you, I'm fine, I'm getting old a little too fast in my opinion.
You're right, it's not a photo montage, it's a complete new engine, I wanted to get closer to the usual configuration for most motorcycles, chain left. All the study and the drawings are finished, I'm in the manufacturing phase. I'm sure you'll notice all kinds of interesting details.

Very interesting indeed Francis. For me the most remarkable aspect is that you moved the gearbox downward and then rotated the engine forward in order to shorten it.
I think your new engine is more compact and better-looking than the Aprilia RSA250 V-twin (below left).
For those who are not familiar with your superkart engine: below is a comparison between the kart layout (mirrored) and the new layout.

[dutchpower]

Hello Francis you change it a lot the transfers !!!

[fpayart]

@ Dutchpower,

Be careful, this photo of the transfer ducts represents the sand cores, with positioning apendices for the central core.
In addition, these are the core for the Suzuki RG500 cylinder which is much narrower than the FPE cylinder.

@ Frits,

I applied myself to compact the engine as much as possible, and also to privilege the mechanical accessibility and the flow of air behind the radiator.
During the study, I considered several configurations, tandem, V ...
Finally I chose a V/tanden.
As I reduced the distance between the two crankshafts, I did not have enough room for the base of the two cylinders side by side, so I opened very slightly cylinders , one with respect to the other (5 °)
And I prefer the dynamic balancing of the tandem, to that of the V one.

[husaberg]

@ Dutchpower,

Be careful, this photo of the transfer ducts represents the sand cores, with positioning apendices for the central core.
In addition, these are the core for the Suzuki RG500 cylinder which is much narrower than the FPE cylinder.

@ Frits,

I applied myself to compact the engine as much as possible, and also to privilege the mechanical accessibility and the flow of air behind the radiator.
During the study, I considered several configurations, tandem, V ...
Finally I chose a V/tanden.
As I reduced the distance between the two crankshafts, I did not have enough room for the base of the two cylinders side by side, so I opened very slightly cylinders , one with respect to the other (5 °)
And I prefer the dynamic balancing of the tandem, to that of the V one.

Very elegant Francis
A similar laylout was on the KR250, of course yours has the contrarotating cranks and is much tidier.

[jellert]

@ Dutchpower,

Be careful, this photo of the transfer ducts represents the sand cores, with positioning apendices for the central core.
In addition, these are the core for the Suzuki RG500 cylinder which is much narrower than the FPE cylinder.

@ Frits,

I applied myself to compact the engine as much as possible, and also to privilege the mechanical accessibility and the flow of air behind the radiator.
During the study, I considered several configurations, tandem, V ...
Finally I chose a V/tanden.
As I reduced the distance between the two crankshafts, I did not have enough room for the base of the two cylinders side by side, so I opened very slightly cylinders , one with respect to the other (5 °)
And I prefer the dynamic balancing of the tandem, to that of the V one.

This is amazing work, so it's actually a 5 degree V-twin with all the advantages of a tandem. Love reading about a massive project like this. Do I spot a wobbly style oval to round exhaust spigot in the second picture?

[Peter1962]

@ Frits,

I applied myself to compact the engine as much as possible, and also to privilege the mechanical accessibility and the flow of air behind the radiator.
During the study, I considered several configurations, tandem, V ...
Finally I chose a V/tanden.
As I reduced the distance between the two crankshafts, I did not have enough room for the base of the two cylinders side by side, so I opened very slightly cylinders , one with respect to the other (5 °)
And I prefer the dynamic balancing of the tandem, to that of the V one.

Bonjour Francis, cela fait plaisir de voir que vous êtes toujours active dans la construction et le developpement de moteurs deux temps de competition.

Now that the rulebook of the superkart is no longer a technical limit, I see that you are using an electronic powervalve. What is your assessment of the difference between the mechanical and the electronic version of the powervalve ? The carburators are of your own creation ? But, this time with electronic powerjet which was prohibited under superkart rules ?

I am so glad to finally see another JBB chassis with a twin cilinder two stroke engine made in France.
The original was in 1981 or 82 if I am not mistaking.

If I may ask : what is the reason that you chose a tandem and not a V twin like the original engine Jean-Bertrand Bruneau used in '81 ? Does the tandem twin have a technical advantage over a V 90° ?

For balancing : can you elaborate on the choice that whas made for balancing, compared to the natural balance factor of a V twin at 90° please ?

[Frits Overmars]

A similar laylout was on the KR250, of course yours has the contrarotating cranks and is much tidier.

It strikes me that in the Kawa KR250 each crankshaft seems to drive a separate clutch gear. To me that only makes sense if each of these clutch gears has its own built-in transmission shock absorber. It won't cure the vibrations of a non-contrarotating tandem-twin though. As far as I know this KR250 was never sold over here.
Can you tell me more about this engine Husa?

what is the reason that you chose a tandem and not a V twin like the original engine Jean-Bertrand Bruneau used in '81 ? Does the tandem twin have a technical advantage over a V 90° ?
For balancing : can you elaborate on the choice that whas made for balancing, compared to the natural balance factor of a V twin at 90° please ?

Peter, I suspect that the crankshaft in the JBB V-twin lacked stiffness because of the long unsupported big end pin and the long distance between the main bearings. Besides, an FPE-version will produce a lot more power than the original JBB-twin.

The natural balance of a 90° V-twin is a fact. But strictly speaking an engine like the Aprilia RSA250 is not a V-twin but a W-twin because of the two separate crankshafts. If those are contrarotating, you can achieve good balance at the cost of high internal forces between the main bearings. If it is not, as in the Kawa KR250, there will be a huge rocking couple that cannot be neutralized without additional balance shafts. Suspending the engine in silentblocs, as Kawa did, is a cheapo solution.

[JanBros]

It strikes me that in the Kawa KR250 each crankshaft seems to drive a separate clutch gear. To me that only makes sense if each of these clutch gears has its own built-in transmission shock absorber.

they have Frits : http://kr250.org/KR_home.htm, under servicing you can find the service manual.

direct link to KR250 service manual of clutch : http://kr250.org/manual/KR_manual_chapter_5.pdf

and indeed, never officialy sold in europe.

[husaberg]

It strikes me that in the Kawa KR250 each crankshaft seems to drive a separate clutch gear. To me that only makes sense if each of these clutch gears has its own built-in transmission shock absorber. It won't cure the vibrations of a non-contrarotating tandem-twin though. As far as I know this KR250 was never sold over here.
Can you tell me more about this engine Husa?
.

It appeared in about 84
it was a 180 degree engine both turned in the same direction.
it had a odd reed and dick intake with the carbs facing forwards.
they had a single one piece head like a RDLC
Later version had a atac type exhaust valve built into the cylinder.
I have the disc measurements somewhere
Pretty sure Europe got the similar single cylinder version.
They were also one of the first Japanese production bikes to have a Ffat slide downdraft carb 28TMSS (like a !KT TZR250)
I have a series of pics tucked away.
https://www.kiwibiker.co.nz/forums/a...id=4840&page=5
They also won the NZ production 250 title when they first came out.

Oh its a series of different teeth on the same gear with the KR250 I assume it just for backlash like the separate teeth on a MB honda counter balancer shaft.
https://www.kiwibiker.co.nz/forums/a...hmentid=307184
Not sure if the hub was rubber shock absorbed but it likely was.

[Frits Overmars]

Oh its a series of different teeth on the same gear with the KR250 I assume it just for backlash like the separate teeth on a MB honda counter balancer shaft. https://www.kiwibiker.co.nz/forums/a...hmentid=307184
Not sure if the hub was rubber shock absorbed but it likely was.

Nah, I don't think so. The shock absorbers were built into the hub of each primary gear, see below left. They were of the cam-type, with spring-loaded lateral movement, like you'll find in a number of British Torrey Canyon-type engines (below right).
The Kawa clutch hub would only contain some springing that pushes the driven gear and the anti-backlash gear against one another, like on the six-pot Honda CBX1000.

[fpayart]

@ Peter1962,
I think Frits answered all your questions correctly.
"Now that the rulebook of the superkart is no longer a technical limit, I see that you are using an electronic powervalve. What is your assessment of the difference between the mechanical and the electronic version of the powervalve ? The carburators are of your own creation ? But, this time with electronic powerjet which was prohibited under superkart rules ? "
Yes, correct.



@ Husaberg, JanBros,
Thank you for this wealth of information

I had never seen that the Kawasaki engine had both an intake by disc and valves.
I was very interested in this engine, but so far I had not found much information

This one interested me a lot too

[JanBros]

This one interested me a lot too

the sad news is that you already show about half of what can be found about it on the net

here's what we at the KR forum have gathered : http://kr-1s.co.uk/forum/viewtopic.p...er=asc&start=0

[jasonu]

They also won the NZ production 250 title when they first came out.
.

Aaron Slight???

[motogpdriver]

could this one be able to do the task?
Don't know if it can handle high rpm's or how accurate it is?
It is designed for 4t

[Grumph]

Husa - I think you may be wrong about the KR250 winning a NZ title. I suspect you're getting mixed up with the KR1 S specials produced by Boyles - and a page added to the manual to aid homologation, LOL.

There have been a couple of KR250's modified for local club racing, neither very seriously as parts are a concern. Frits may be amused to learn that invariably the first thing done is to re-phase the cranks. Both the modified ones I know of are now parked up permanently.
I also know of one still on the road which has also been re-phased. More because it simplifies the ignition once the original fails.