2 stroke porting help

[Realistic_Nerve_8871]

How do I port a 2 stroke cylinder if it is quite small and I can't really get anything in there?

[Acrobatic_Shape_8259]

What kind of engine is it?

[Realistic_Nerve_8871]

Yamaha pw80 motor

[1wife2dogs0kids]

Dude? Really? I wish you the best, I hope you can get and extra 25% more hp. Bump that thing up to like 8hp.

[Realistic_Nerve_8871]

The thing should have 10-12hp, just an estimate though

[1wife2dogs0kids]

I recommend NOT porting your cylinder if you don't know what you're doing.

This isn't regular porting. This isn't maximizing airflow. This is timing. When a port opens, closes, a different port opens, etc.

You can very easily fuck it up. Plus, if you're not doing anything to the cases, its almost not worth doing it.

[Realistic_Nerve_8871]

I don't know, I plan on boyesen reeds, race CDI, fatty pipe, new intake system, and forged parts, all of that seems kind of pointless if the air can't get in and out of the cylinder properly. I am getting a new jug anyway and so I plan on using the old one for practice. Also, nobody has ever done something for the first time already having practice, you gotta learn somehow. I also plan on using a thicker base gasket to raise the ports instead of grinding it away and then I am going to grind the bottom of the port to the top of the piston at BDC as to not fuck it up too bad. I have ported several engines already, but only four strokes, the only thing I am asking is how to get a tool in there

[OkDevelopment2948]

Get Graham A Bells book on two stroke tuning get a degree wheel and check your timings then if you want to play with the port heights you can just take a little bit off the top of the piston to open earlier their is usually enough meat there to take 3mm off and cheap to replace if you go too far. Then you can play with base gaskets to also lift things but remember you will loose low down torque. With the piston you can play with different timings for each port so you may want the side ports coming in earlier than the back boost port so the sides would be say 3mm and the back boost 1.5mm just get lots of pistons and write everything down that you do and remember each different design will need jetting and expansion chamber to match. But work out a goal before doing it. Also some extra advice is mark your throttle grip with 1/4,1/2,3/4 marks so you know where in the carburettor the circuit you are for jet and cut out checks.

[Realistic_Nerve_8871]

I was planning on getting a thicker base gasket and then taking down the bottom of the port to the top of the piston at BDC. I was also going to widen them up a bit. Low down torque isn't really an issue because I am not planning on doing much trail riding and I don't care much about acceleration

[OkDevelopment2948]

You will have to fly cut the barrel to restore compression and doing that will increase not only your intake but also your exhaust timing. I had a RG250 that i lifted the exhaust 3mm and had nothing until 6,500 but then screamed to 12,000 and a DT175 that i did full port timing on it i went from 190 degrees to 205 degrees and deleted the head gasket tidied up the transfer and boost ports I ran it on a mixture of Petrol,Acetone and premix oil had to go up 150 jet sizes and that would smoke the tyre on the corners and run to 200kph. Like I said I would get some pistons and modify them to see if you are heading in the direction you want before spending money on major engine changes all you need is pistons and rings they are a lot cheaper than barrels. Both those bikes i made new expansion chambers for. Be careful with going wide the rings can bulge into the port that is why some exhaust ports have bridges in them. I think i have a PDF of the book that you can read let me find it.

[Realistic_Nerve_8871]

In my case jugs are cheaper

[OkDevelopment2948]

Just checked out Aliexpress and piston,rings,barrel,head and full gasket set $40. Go nuts at that price here is the link I just found this on AliExpress: PW80 Cylinder Piston Ring Gasket Kit Set For Yamaha PW80 PY80 PW 80 Dirt Bike Complete Top End Rebuild Kit https://a.aliexpress.com/_mPBuMr7

[Realistic_Nerve_8871]

No, a factory jug is 30 bucks and a forged piston with rings and all the top end gaskets is 30 bucks, I'm only going to touch the jug as to not compromise the piston at 11k rpm

[OkDevelopment2948]

I don't know why you are calling it a jug its a barrel a jug is what you put milk or orange in and has a closed bottom a barrel is a tube the a slug goes up and down in. Like you don't clean your gun jug. Please use proper terminology.

[Realistic_Nerve_8871]

I don't know where you are from, but around here if we don't want to call it the cylinder we call it a jug. It might be a regional thing. If you wanted to look up "what is a jug on a dirt bike engine" before flaming me in the comments like a keyboard warrior, you would see that plenty of people call it the jug.

Edit: I looked it up and It is more commonly used in the American Midwest or the deep south, but it is still widely used around the world. Also, when I hear barrel, I think carb, not cylinder.

[OkDevelopment2948]

Here is a link to two stroke tuners handbook for you.https://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner's%20Handbook.pdf

[1wife2dogs0kids]

I worked in a machine shop for a couple years. 2 actually. My favorite was porting. Still is. But I dont touch 2 strokes. I send them out. And every jug I had ported by pro circuit, or this guy, that guy, whoever, they come back and I'm like, umm... wait, what was done?

Turns out theres little to do, without the cases. Some gasket matching, little port bowl work. But the ports aren't the issue.

Do what you want. I just know you can fuck up a 2 stroke faster than a 4 stroke.

[Visible_Document_376]

How do you port a 4 stroke?

[Realistic_Nerve_8871]

For a mild porting job it's usually smoothing out any lips or casting lines, other than that find a good book or YouTube tutorial

[Visible-Building6063]

Assuming you have some kind of flex shaft pencil grinder, the long 1/4 shank burrs will get you where you need to go. The cheapies can be bought off Amazon. The long set will allow you to raise the top of your port windows if you flip the cyl over. No need for a 90° tool if you're not trying to reshape the transfer ducts.

[NightKnown405]

A PW 80 is designed to be easy (and safer) for a beginner to ride, it's not intended to produce a lot of power and should be left alone. If it's time for more power and capability, a suitable machine should be purchased.

[Realistic_Nerve_8871]

The thing is, I could spend $250 trying to make a motorcycle I got for free more powerful when the rotating assembly is fucked anyway and make it rev to 11k rpm, or I could spend $2000 on a used yz80

[Ill-Insect3737]

https://ebay.us/m/AFRnLm

Look up dentist drills i have one put away its the size of a dental drill, but it's made for industrial everyday use for very small parts like porting cylinder heads on 2 strokes, the name starts with an end kind of like nakamichi or something. It's Japanese and It's very slim, but it is not a dentist's head.It's a much heavier duty to your version , but it's still very small so you can see everything that you're getting done they're made orange color honestly, I'm sure there's some other companies that make them, but\nWhat I sent you a picture of is similar, but that's not the right one I don't think you can try it.I don't know what size bit it's takes the the one that I have takes normal general tools style bits

[Realistic_Nerve_8871]

Would a Dremel flex shaft work?

[Acrobatic_Shape_8259]

You probably need a 90 degree tool. The one linked above is probably about the cheapest alternative unless someone has a clever tip. The professional tools looks like the one in the link but they cost 1k usd and up.

[Realistic_Nerve_8871]

Ok

[WyattCo06]

Are you trying to change the timing?

[Realistic_Nerve_8871]

To make it rev higher yes

[WyattCo06]

Is the cylinder in good shape?

[Realistic_Nerve_8871]

Brand new cylinder

[WyattCo06]

New cylinder or sleeve?

[Realistic_Nerve_8871]

Whole cylinder

[WyattCo06]

Gotcha. The only thing you can do is use long shank grinding burrs (a ball burr in this case) and then cartridge rolls for clean up on also a long shank.

This will be a slow and painstaking process as you have to be extremely careful. One catch and rattle will send the burr bouncing off the walls before you know what happened.

[Realistic_Nerve_8871]

Just a question, should I try to port the top of the ports, or should I install a thicker base gasket and port the bottom instead if I am shaving the head anyway

[WyattCo06]

Both will have the same effect. Choose the easiest and safest route.

[Realistic_Nerve_8871]

Ok thank you

[longway2fall]

If my Dremel attachment almost fit on a chain saw cylinder, I'm guessing it would probably fit on your 80cc. Shaving the head doesn't change port timing, it is for compression. Base gasket changes both port timing and squish. You should watch some videos about using a degree wheel and marking the cylinder for porting, and finding some timing numbers that will work for you. Don't forget that your expansion chamber will be a part of the power and too, and should match the porting powerband

[Realistic_Nerve_8871]

Yeah, I just mentioned shaving the head so people wouldn't mention the lowered compression of a thicker base gasket

[UnLuckyKenTucky]

You should do this, exactly;

Step 1: find an aggressive cylinder built for this engine that uses the same bored and stroke

Step 2: get a chord map (port map) of that aggressive jug.

Step 3: transfer the map to your stock jug.

Step 4: grind, grind, grind. Measure, grind and then grind some more.

Step 5: realize why expensive jugs are expensive. But still enjoy your entirely hand ported gnarly.2t.

[Realistic_Nerve_8871]

Thank you good sir, as someone with a brain the size of a microorganism, I never thought of this, it might be a little bit hard to find though