Many many many many engines have that phenomenon going on. Nothing out of the ordinary. Not likely due to anything other than a cause of mass production; multiple uses for some parts for different engines. In a lot ofncases with engines using a single exhaust port, the port cannot be too wide or the piston doesn’t get enough support throughout the stroke and can therefore wobble a little and catch the edge of the port. This is what caused the multi-port exhaust porter engines to come about.

If the crankcase is blocking some flow you can always enlargen it w/o touching the sleeve.

I think this is a left over from very old plane engines where the sleeve is placed in a 45 degree position

To clarify, I was asking if it is helpful to bevel the outer edge of the exhaust port in the sleeve to match the shape of the exhaust port in the crankcase. The idea is to remove sharp edges that might interfere with returning pressure pulses, without changing the size of the exhaust port.

OS and their clones rotated the liner. No one else did this to my knowledge.

NO. It will do NO good.

Why not?

Because some things just don’t do anything worthwhile. I’ve done similar things on some engines and it made no more power than it did beforehand. If anything, it made it harder to get the needle setting just right. It messes with a thing called the “boundary layer”.

The boundary layer? I've heard that term before, but never in the context of engines. I looked it up in the Two-Stroke Tuner's Handbook, but I'm not seeing any information about how beveling the outer edges of the exhaust port to match the crankcase would make the boundary layer around the perimeter of the port thicker. If anything, the boundary layer should be thinner, and flow through the port higher, as a result of there being fewer sharp edges to catch the exhaust flow.

Credit where credit is due: Roelof's prediction of what would happen if I removed the lip at the bottom of the exhaust port was exactly correct. The engine didn't become any more powerful, and fuel consumption increased. Lesson learned.

Stop waisting time removing material from the engines, and send the engines to a tuner like Abmods or Murnan for optimal tuning.....Come on guys stop the BENCHRACING !!!.....

Why? There is nothing wrong with experimenting on cheap engines as long you keep in mind it will never be a winner.

I am all for DIY and basically anyone can modify engines as long you can measure timings and know what to do. Use other engines to measure timings, set them in a list and note the feeling of the engine. With plenty listed you can see which rimings does what what will be a base to try some more. And yes, going beyond of what you see will be a trial and error

Why, because you will benefit from the tuner's experience in the long run. You'll be surprised to find that old motors can still win once they're modded right...I am not saying to not try your own mods, but consult as many modders as possible before you do.....

1) Removing material is how all engines are modded.

2) How do you think the good modders learned which mods actually work?

3) They would laugh at the engines I'd send them anyway.

Understood, but looking at the Abmods website I see a whole bunch of dynos of old extinct engines that rock after the mods. I run the abmods tuned jlr.12 against the new crop of motors, and pass a whole lot of them down the straight. I don't know if he has seen your motor before, but I doubt that he won't be able to make it faster... Cheers....

You are forgetting the fun, how learnfull and at the end how cost reductive it is.