ESE's works engine tuner

[Jan Van Hamme]

If you do it from scratch, why dont you take a domed, single ring piston?

Cant remember any advatage of the flat ones...

Then positioning ring gap in the middle of c port...you are more free doing minimum bridges between b and c ports...

Have a look at oler yamaha yz pistons
Or on suzuki rm 125...we use wössner too..

Exhaust t port?...the bridge is a weak point...not as sturdy as triple port layoutļ

Just my two cents ��

Wolfgang

Hi Wolfgang, thanks for your reply.

It's an RD125LC. I've chosen to limit my rpm to 10,000 rpm.
If I cut out the bottom of the skirt (like with the old YZ125H), there's not much support left against piston tilt.
I'm thinking of making my own windows (two or three).
That way, I'll have some surface area left over to provide support against tilting.
That's why I opted for two piston rings, for the engine speed and a bit more resistance to rattle.

It's a VHM connecting rod (110 instead of 105).
I haven't found any 56mm pistons with two rings, a dome, a 15mm pin diameter offset by 1mm, and a lower compression height that I can shorten or drill holes in (cylinder intake reed valve).
Wössner did have them. That's why I was forced to use the flat piston.
The plan is to install a torroid insert.

On this piston, the ring gap of both piston rings is in the center of the C port. One is directly in the center, the other a millimeter off center.

A single exhaust port (70% and safe roof) is sufficient for blowdown and low timing for the intended power and rpm.
Therefore, I would opt for a T-port or triple exhaust port.

I'm not sure if the distance between the exhaust and the A-port is large enough to prevent shortcutting.

Vriendelijke groeten,
Jan

[Wos]

Hi Wolfgang, thanks for your reply.

It's an RD125LC. I've chosen to limit my rpm to 10,000 rpm.
If I cut out the bottom of the skirt (like with the old YZ125H), there's not much support left against piston tilt.
I'm thinking of making my own windows (two or three).
That way, I'll have some surface area left over to provide support against tilting.
That's why I opted for two piston rings, for the engine speed and a bit more resistance to rattle.

It's a VHM connecting rod (110 instead of 105).
I haven't found any 56mm pistons with two rings, a dome, a 15mm pin diameter offset by 1mm, and a lower compression height that I can shorten or drill holes in (cylinder intake reed valve).
Wössner did have them. That's why I was forced to use the flat piston.
The plan is to install a torroid insert.

On this piston, the ring gap of both piston rings is in the center of the C port. One is directly in the center, the other a millimeter off center.

A single exhaust port (70% and safe roof) is sufficient for blowdown and low timing for the intended power and rpm.
Therefore, I would opt for a T-port or triple exhaust port.

I'm not sure if the distance between the exhaust and the A-port is large enough to prevent shortcutting.

Vriendelijke groeten,
Jan

Ok jan

I stuck with bore of 54.5 for a 125cc

But we run a 125 with adaptet reed valve to cilinder that has down skirt a cutout...and 2 Windows to, with only one ring...absolutely no problem...the wössner is stiff enough...35 h no ploblem


...doing a printed cilinder...wow ...dont you think about changing bore and stroke to square?
...every kind of pistons avaiable...and next to best bore stroke ratio...

Some Pages earlier frits gave a rule of thumb, about minimum space between ports...

Formula was bore x 0,044

If this rule is applyable to bridge between Ex and A port...you should be save



Keep us informed about...especially printing your dream cilinder!

Wolfgang