ESE's works engine tuner

[Mollihead]

This is italkit vertex... look at last picture to clarify Dimensions 😉

Comp hight 25,2

https://www.langtuning.de/Italkit-Ra...m-Kolbenbolzen

Comp hight 28 but 12mm pin
Maybe change needle bearing 😉

https://www.langtuning.de/LT-Perform...n-90-ccm-50-mm

I already ordered this piston and sent it back after I found out that the piston is too short for 50mm stroke. Exhaust port opened at TDC.

The only piston I found is a Polini Evolution P.R.E
Ordered it with 49,935 and received one with 49,915 diameter
Now I don‘t know whether I should give it a try with 8,5 1/100mm clearance…

[Mollihead]

By the way: in case there is a needle bearing which converts 14mm to 12mm it could be an option.
The only one I know of is offered at EMOT racing page. But it’s always marked as sold out.

[Wos]

By the way: in case there is a needle bearing which converts 14mm to 12mm it could be an option.
The only one I know of is offered at EMOT racing page. But it’s always marked as sold out.

Ex open in tdc??? Really?

New nikasil coating or do a ptfe piston coating for 0,05 to 0,06 mm tolerances
Would be the expensive way....

Talk to emot! 😉 but many dealers have conversion bearings...

Would be nice to hear more ...engine...what you are aiming for...upper needle bearing outer diameter... wide? 😉


But why going that way???

Easy job to take off 3 mm on cilinders downside on a lathe ...then the italkit should fit!?

Pretty much easier than milling case 😀

[Mollihead]

@Wos

The Italkit piston from Langtuning has a skirt length of 46,5.
Therefore it opens Exhaust at TDC in case 50mm stroke.

Regarding the bearing:
At the moment I use a Kart bearing 14x18x16,7 Inner diameter x outer diameter x width
So a conversion bearing should be something like 12x18x….

[Mollihead]

The project is to squeeze out a Zündapp Zuntrade cylinder. Thermosyphon cooled.
Originally 92cc (with 47mm stroke).
Now I have a 50mm crankshaft. Therefore port heights are adjusted accordingly.
Transfer widths are limited - so I extended it with JB Weld.
Added boyesen ports and extended the inlet area to run a VForce 3 membrane.
Since there is not much material left I can’t mill down the bottom end several mm.
Already had a crack in this area in the past.
The last cylinder reached 22,5HP at the wheel before the crack happened.

[41juergen]

I need new big end bearings for a TZ250 4DP. The stock Yamaha ones cost approx. 115,-€! Does anyone have an idea were to get silver caged bearings, ID 24 mm, OD 31 mm, width 16 mm..

[Wos]

@Wos

The Italkit piston from Langtuning has a skirt length of 46,5.
Therefore it opens Exhaust at TDC in case 50mm stroke.

Regarding the bearing:
At the moment I use a Kart bearing 14x18x16,7 Inner diameter x outer diameter x width
So a conversion bearing should be something like 12x18x….

Nice " Stoiga" racer from zündapp 😉

Short piston skirt is opening INLET port earlier...but not ex port

But does this matter on a reed valve inlet?? Opening timing is done only by reeds... confused...

I was wrong that its easy to find this special needle bearing

Grüßle 😉 Wolfgang

[Mollihead]

Finally found one today, which I think is from same source as the EMOT ones

https://2taktteile.de/products/adapt...d961c628&_ss=r

[Mollihead]

Nice " Stoiga" racer from zündapp 😉

Short piston skirt is opening INLET port earlier...but not ex port

But does this matter on a reed valve inlet?? Opening timing is done only by reeds... confused...

I was wrong that its easy to find this special needle bearing

Grüßle 😉 Wolfgang

Hi Wolfgang

I try to show it in the picture. In case length of skirt is shorter as the stroke you can see through the exhaust port in to the crankcase in case piston is at TDC

Gruß zurück Wolfgang

[Wos]

Hi Wolfgang

I try to show it in the picture. In case length of skirt is shorter as the stroke you can see through the exhaust port in to the crankcase in case piston is at TDC

Gruß zurück Wolfgang

Thanks Wolfgang for helping me with picture...never seen...but got it now

[Mollihead]

never thought about this before until Wobbly somewhere mentioned this. But it’s long time ago…

Now I’m looking for a 50mm piston with
12mm pin
And >=28mm comp height
And skirt length >=50mm
And ring pin at 6 o‘clock

but seems to be not easy as well.

[Wos]

never thought about this before until Wobbly somewhere mentioned this. But it’s long time ago…

Now I’m looking for a 50mm piston with
12mm pin
And >=28mm comp height
And skirt length >=50mm
And ring pin at 6 o‘clock

but seems to be not easy as well.

Lieber Wolfgang

New idea! 😉

Why to stuck with 50,00 mm bore...

For long therm its good to take parts as bearings and pistons that are available everywhere...and overbore the cilinder...replate it

[Mollihead]

Nice idea
But as mentioned the cylinder is already at the limit of stability.
Therefore I asked some pages back for the maximum inlet width.
I had crack in the piston and cylinder inlet bridge at the same time.

[Mollihead]

My feeling is that many of the available MX pistons are designed to run in a case membrane engine and therefore they have a narrow skirt at the inlet side.
If you use it in a cylinder membrane engine the support at the side is missing and therefore the area pressure at the bridge will be too high at downstroke after combustion

[Wos]

Ask barikit for specific ringpin pos

https://barikit.de/collections/kolbe....kolben_c=53.5