ESE's works engine tuner

[Frits Overmars]

Mr. Frits, please take a look at these channel cross-section sketches.
Is it possible to consider such an interpretation of the cross sections of the purge channel profiles?
With the graduation channel, I'll probably work with the sketches before starting to build 3D models, and of course I'll show the result.
It probably wouldn't be a bad idea to attach a profile of the piston bottom, I didn't think about it right away.
I'm laying the piston with a sphere with a radius of 360 mm and a compression height of 30.5 mm.
I stopped at a connecting rod with an inter-center distance of 129 mm. At least this size seemed to me more optimal in terms of calculating lateral forces.... Well, what will happen with gas exchange and filling, it will probably have to be evaluated only in bench tests.
The engine is still being drawn and is in the stage of sketches and layouts.

Thank you DSE. Yes, I prefer to be called just Frits, without the 'Mr' or even the 'Dr' that Germans seem to be so fond of.
And of course everybody is free to use the nickname he or she prefers on the internet, be you would make me happy if I could call you by your first name too.

Your posts raised a number of questions. And I guessed wrong with your 'jumper' so now I will simply ask instead of guess: what is a graduation channel?

Your engine has a 69,5 mm bore and a 65 mm stroke so it's definitely short-stroke which as you may know, is unfavorable for the specific angle.areas in a two-stroke engine.
Your 129 mm con rod length is less than twice the stroke. If I were free to design an engine, I'd use a rod/stroke ratio of 2,2 , so noticeably longer than you are planning to use.

You wrote that you studied the 'tower of Pisa' concept but it does not show in your drawings. Your axial transfer angles are steeper than the proposed values in my concept,
which is meant for a square bore/stroke engine. For your short-stroke engine those angles should be even smaller.

The most import radial transfer angle is the leading direction angle of the A-transfer port. Why make it 40° instead of 30° if you still enjoy the freedom of the designing stage?

[koenich]

Let me know once they are available

[DSE]

Thank you DSE. Yes, I prefer to be called just Frits, without the 'Mr' or even the 'Dr' that Germans seem to be so fond of.
And of course everybody is free to use the nickname he or she prefers on the internet, be you would make me happy if I could call you by your first name too.


The most import radial transfer angle is the leading direction angle of the A-transfer port. Why make it 40° instead of 30° if you still enjoy the freedom of the designing stage?

I understand you.
Of course, I'm not German, but where I was born and raised, at an early age, respect for people older than you is embedded in education, and even more so for those from whom you study.

I do not know the correct equivalent in English, as I could in general. If I offended you, please excuse me.
My name is Slava, among colleagues and friends.

Now, regarding the radial angle of the purge channel, I will have to clarify.
I assumed that for an engine with a cylinder volume of 250 cubic centimeters, I would be able to use a backup crankcase from the 193 cc engine, which I had designed and manufactured earlier. And on it, the attachment points of the cylinder are very close. And it is difficult to deploy the purge channel. Now it becomes clear that I will have to design and manufacture a new engine crankcase. .
Here he is, 193 engine.

[DSE]

Your engine has a 69,5 mm bore and a 65 mm stroke so it's definitely short-stroke which as you may know, is unfavorable for the specific angle.areas in a two-stroke engine.
Your 129 mm con rod length is less than twice the stroke. If I were free to design an engine, I'd use a rod/stroke ratio of 2,2 , so noticeably longer than you are planning to use.

I also understood the axial angles, I'll also redo them and show them. There is, however, a slight problem in this, in my opinion, when processing the sleeve, but I think that a 5-axis machine can handle it.
I also realized from the connecting rod that I would have to postpone the workpieces and "draw" a new connecting rod.
On the 193 engine, by the way, I have a connecting rod with a ratio of 2.15.
I've been wanting to make a connecting rod like this for a long time, but somehow I can't get my hands on it. Now you'll definitely have to do it with a 2.2 ratio.
(p.s. - again, he writes nonsense, the ratio of the length of the connecting rod to the stroke of the piston, Google interprets in its own way..)

[DSE]

Your posts raised a number of questions. And I guessed wrong with your 'jumper' so now I will simply ask instead of guess: what is a graduation channel?

I'll be watching more closely what Google translates.

[koba]

we weren't able to find the right match with the original cagiva gear spacing, so we always lacked the right timing in super slow corners.. this low revs config helped us covering this problem.
anyway we'll develop some more during the off season to gain something revving higher.

in the coming weeks i'll have a pair of derbi (but euro3) cylinders to begin playing with. I want to finally develop a credible alternative to the very good bidalot kit.

I cover this problem with clutch abuse.

(Not close to the same power level).

[Gradella23]

I cover this problem with clutch abuse.

(Not close to the same power level).

it helps!
unfortunately we were racing with an almost 90kg street production bike Cagiva Prima, against some handmade and/or proper racing bikes with magnesium rims, great suspension, and weighing 65kg so having some more power down low was even more valuable

[Frits Overmars]

I assumed that for an engine with a cylinder volume of 250 cubic centimeters, I would be able to use a backup crankcase from the 193 cc engine, which I had designed and manufactured earlier. And on it, the attachment points of the cylinder are very close. And it is difficult to deploy the purge channel. Now it becomes clear that I will have to design and manufacture a new engine crankcase. Here he is, 193 engine.
I also understood the axial angles, I'll also redo them and show them. There is, however, a slight problem in this, in my opinion, when processing the sleeve, but I think that a 5-axis machine can handle it.
I also realized from the connecting rod that I would have to postpone the workpieces and "draw" a new connecting rod.
On the 193 engine, by the way, I have a connecting rod with a ratio of 2.15.
I've been wanting to make a connecting rod like this for a long time, but somehow I can't get my hands on it. Now you'll definitely have to do it with a 2.2 ratio.
(p.s. - again, he writes nonsense, the ratio of the length of the connecting rod to the stroke of the piston, Google interprets in its own way..)

Thank you, Slava. I see that your “freedom of the design stage” is not unlimited, as I had assumed until now.
A connecting rod/stroke ratio of 2.15 is acceptable. But a 250cc single with a cylinder sleeve and an exhaust centre bridge is asking for thermal problems.
Your pictures have made me curious. How do you use an engine without a gearbox on a kart? Does it get an automatic clutch or a CVT transmission?
I find the spark plug caps interesting. Where did you find them?
As for Google Translator, I don't use it anymore. The translator from Deepl.com is much, much better.

[porttiming124]

Hello, I'm looking for a 67.5mm cast piston with an 18mm pin.
I'm from Canada and I can't find anything good here or in the United States. Do you know of any brands in your country? Thanks.

[DSE]

Thank you, Slava. I see that your “freedom of the design stage” is not unlimited, as I had assumed until now.
A connecting rod/stroke ratio of 2.15 is acceptable. But a 250cc single with a cylinder sleeve and an exhaust centre bridge is asking for thermal problems.
Your pictures have made me curious. How do you use an engine without a gearbox on a kart? Does it get an automatic clutch or a CVT transmission?
I find the spark plug caps interesting. Where did you find them?
As for Google Translator, I don't use it anymore. The translator from Deepl.com is much, much better.

I bought these ignition coils when my friend was making a programmable system. This is from Suzuki's outboard motor. Coil tips: - fluoro-rubber. I use a centrifugal clutch (pictured below), but this decision is not final.

I found one here: - ..https://aliexpress.ru/item/100500860...type_rcmd=core

[DSE]

I'm looking at such a model, I would probably try it.
I'm falling asleep now, and I'm going on a business trip tomorrow.

I'll answer any questions in a couple of days.

https://www.bmikarts.com/Bully-34-Tu...M_p_20809.html

Regards

[dtenney]

Frits, Wobs or others: Is it important to have the rotary valve drive balanced to offset the imbalance of the rotary valve itself? We are thinking there may be additional power to be gained with a balanced disc.