So anyways, it's irrelevant which one revs higher or faster. The point is comparing a 2-stroke port job performance to a 4-stroke port job is like apples & peaches. They are two different animals and behave totally differently. 2-stroke engines have no bottom end, they have a power band, which is ALWAYS up there in the revs.

Bubba... If you really want to do this, find yourself a big washer that fits snugly inside your header pipe. You will use this as a guide to open up the exhaust port. You can take measurements and get all fancy, but the bottom line is that you want to match these up so numbers don't matter. If you don't remove the valves, stuff some paper towels down in there deep & tight, use compressed air to blow out the dust and filings. Grind a little all around, test fit your washer & make adjustments where needed. Go a little at a time. Once you've got it opened up, smooth everything out. You don't want any sharp or abrupt edges. Imagine how the exhaust gases are gonna flow & make it as smooth as possible. A dremel will be a slow process, but that's ok too. I use a bur bit, which will take off a lot of meat really quick-like. Then I finish up with a fine stone (dremel) to smooth it all out.
On the top of the exhaust port there is a big flat spot with a lip on it. You can see it in every picture posted, although you can't see the lip because it faces away from you. I call it "the ledge". Stick your finger in there and rake across it a few times, you will feel the lip. I removed a considerable amount of material there, but at bare minimum you will want to take off the lip and round off the flat spot so everything will flow smoothly. This is probably the hardest part of the job, but once you stick your finger in there & rake back a few times, it becomes obvious what needs to be done.

Serowbot is right on the money with the intake side. Roughness on the walls is better but you still want everything to flow smoothly. There is a stud protruding out right in the middle of the port & that cannot be good. It took me about 2 minutes to cut that thing down with a bur bit. It's a threaded stud, not aluminum.

The reason you want to leave the intake port walls rough is because of a phenomenon called fuel drop-out. That's when smooth walls let fuel droplets collect on them, then the droplets don't stick & just run down the sides and collect at the bottom. With rough walls, the fuel droplets kinda stick & are less likely to run down & more likely to be picked up by the air mixture surging by. Rough walls also promote more turbulence which helps atomize the air/ fuel mixture & therefore allow for a better, more complete burn in the cylinder.

On the flip side, get the exhaust port as smooth as possible. These walls aren't collecting any fuel droplets (hopefully). The idea is to make it as easy as possible for the gases to be pushed/ pulled out.

Now please don't take what I say as expert advice. Do some research on it. I'm not a professional by any stretch but I have ported several heads over the years from 2-stroke & 4-stroke quads, bikes, to air cooled VW's. Keep in mind my goal was never to increase fuel mileage, but to increase efficiency & power. This advice is only worth what it cost you!

earlytimz, thanks for the info. I've read here about exhaust porting and I've been curious about it (just becuz). anyway, I'll continue to research it (altho' it seems folks that have done it like it!) and may give it a shot over the winter when I have riding downtime. Right now the weather has been great here and I don't want to dig into it.
Thanks for the description...even if Bill didn't read it...I did...

Babyhog...+1
just tryin' to learn something here...

Quiz     Which is turning faster  2 cycle 6000rpm   4 cycle 6000 rpm electric motor 6000 rpm.

Makes you wonder, why Suzuki even designed the exhaust port that way. The must be a reason for that restriction.

bill67 wrote on 06/09/10 at 10:38:03:


Sorry Bill, you just sound silly now.

Bill67 - My young fellow 4 cycle motorcycles rev higher than 2 cycle,I've had 3, 2 cycle motorcycles.

Earlytimz - 2 strokers only have 1/2 the revolutions to make a complete cycle. They rev twice as fast.

Ones of you is saying "revs higher" the other "revs faster". In my mind "revs higher" means higher redline and "revs faster" means less time from idle to redline.
Still...if you have a 250 single 4stroke vs a 250 single 2stroke both at 6000rpm the 2 stroke is going to put out more power. It will go through its combustion cycle twice as fast. Right?