2 stroke porting

[Tom Brown]

I'm toying with the idea of building a CNC device to port 2 stroke cylinders. I think a homebuilt device could be plenty accurate enough for cylinder ports.

How do you guys port your 2 stroke sleeves?

[itsme]

Hi,

If you're planning on building a machine, I would simply go with a 4-axis CNC mill. Something like a desktop mill (Sieg X3 maybe???) with a fourth rotary axis would probably do, depending on how big your liners are.

You could then mount the liner on the rotary axis and proceed to mill the ports. With a setup like this, your porting possibilities would be almost endless and they would also be repeatable.

The other advantage of using a mill is that it is useful for so many other things too. It wouldn't just be limited to cylinder liners.

I hope this helps.

Regards
Warren

[wsuwrhr]

Tom brown, is this you?

[HPbyGD]

Are you taking about trying to port a cylinder or just cut the ports in a liner? Cutting a liner is a pretty simple job with 4 axis. Porting a cylinder is going to be a lot toughter.
Gary

[Tom Brown]

Originally Posted by HPbyGD Are you taking about trying to port a cylinder or just cut the ports in a liner?

Port a cylinder. The bores will be 3.500" ID. Mercury 260 outboard.

Originally Posted by wsuwrhr Tom brown, is this you?

Fabled in story and song. I built a CNC hotwire several years ago and now I'm working on a CNC router largely based on Joe2006chevy's 2006 r2 model.

[zcases]

I have done extensive work on 2 strokes. The best tools for this are hand grinders......but please dont think "dremel" when I say that. Unless you are just planning exhaust and intake work, you need a real good collection of straight, 45 degree, and right angle grinders and a Foredom (or similar) flex shaft machine to properly reach the transfer ports. This is about a 300 dollar tool, look for CC Specialty tools, or Gesswein for the right angle tools. Most of the work is actually on the paper - designing the shapes and areas.

[nick.gilling]

I think he means to cut the ports, not to smooth everything out for better gas flow

[itsme]

Hi,

I assumed you were talking about liners, so my suggestion is probably not the best for complete cylinders.

Maybe you could supply a few more details. Are you making completely new cylinders or are you trying to modify the standard factory cylinders?

Regards
Warren

[Tom Brown]

Originally Posted by itsme Maybe you could supply a few more details. Are you making completely new cylinders or are you trying to modify the standard factory cylinders?

Actually, I want to put a 280 port map on 260 cylinders. It would be nice if I didn't have to install 6 sleeves to do that but sleeving an engine wouldn't be the end of the world, either.

It's just an exercise, really. I can send a block out and have it done up for a couple of thousand so there isn't a ton of money to be saved. It's more a matter of wanting to do it myself.

Any time I've seen an engine that someone has opened the rod slots, lightened pistons, or whatever... with a die grinder, it always looks like it was done by rats. I would love to be able to get all cylinders identical within about 0.002" and have it look like it is a stock port map.