Porting Stock e50 Cylinder?

Sasha Alexander /

I've heard mentioned here "porting the stock cylinder". I'm not sure what this means. I'm rebuilding my e50 (stock) right now and I'm wondering if theres anything I can do to increase performance of the stock engine. I'm already getting a new pipe, intake and jet. I read the wiki on porting/case matching but I don't really understand how this applies to the stock cylinder. I couldn't find any tutorials or instructions on it. If anyone could explain I would really appreciate it. I've got the case open right now and I'm ready to do some damage.

Re: Porting Stock e50 Cylinder?

Overpriced Parts /

Just make sure you got a 1.5-2hp cylinder not a 1 hp

Re: Porting Stock e50 Cylinder?

Sasha Alexander /

yeah its a 1.5

Re: Porting Stock e50 Cylinder?

Not to sound like a killjoy, but if I were you, I would say do A LOT more reading before you dive in if the wiki article doesnt make sense yet. I just recently started porting but I was reading/researching for a few months before I was comfortable with actually doing anything.

Basically case/port matching is getting rid of all the casting flaws in your cylinder/case to where you have a nice, smooth flow throughout the entire engine. This reduces turbulence which kills engine efficiency and robs you of power that you could otherwise be getting. This will also involve cleaning up port edges (port chamfering) to smooth flow but NOT changing the shapes/sizes of the ports (not yet at least). Most people do this on aftermarket cylinders as well to ensure proper flow through the engine.

Actual porting/port reshaping is a different story. That is taking a stock port map (read up on port maps) and changing it to what you want. This involves some math usually, and a good bit of know-how as to what you are doing (otherwise you may end up with a fancy doorstop/paper weight).

As for tutorials, you can search "two stroke porting" or something similar in google and youtube. I found a good tutorial on youtube one time, but I couldnt begin to remember what it was (I do know he was just doing some port matching).

Tool wise, most people here use dremels (I do personally) with various grinding and cutting tools, hand files, sand paper, etc to achieve porting work. In order to work on transfer ports you will usually need a right angle pencil grinder, which is about 150 bucks for a cheaper one.

TL:DR - Do some more reading/researching so you can get a better understanding before you dive in. You don't want to ruin a good cylinder without meaning to.

Re: Porting Stock e50 Cylinder?

Sasha Alexander /

Ok. It makes more sense now. Your explanation is really helpful.

I get port matching but I didn't realize that stock cylinders had flaws I thought they were perfectly matched already. Reshaping is beyond my knowledge of course at this point.

Im new to this so yeah probably a good idea to not mess things up.

Will continue reading. Thanks again.

Re: Porting Stock e50 Cylinder?

You can widen the throats of the ports without worrying about fucking anything up, and also, widening ports laterally by a few mils, as long as you don't get into your ring gap, is pretty safe.

actually Im about to start working on a pinto, so I will do a port map for a 2hp e50 and do some of the relevant maths. I'll get back to you in a few hours.

Re: Porting Stock e50 Cylinder?

Yea don't be intimidated.

Re: Porting Stock e50 Cylinder?

#3 open transfer, exhaust raised 1.5mm widened 3mm, intake lowered 1mm widened 2mm, cut skirt on intake side 1mm (more if needed to clear @ tdc) .Cheap easy fun set up with a 14 bing and derestricted stock pipe (proma gp is much more fun).

Re: Porting Stock e50 Cylinder?

Downhill Harvey (OFMC) /

I've never understood what makes a noob, with a dremmel, think that they can do better than the factory. Leave it or kit.

Re: Porting Stock e50 Cylinder?

Iam sure even a "noob" could gain some performance by cleaning up any casting flaws from the factory.Most of these brand new kits have the same type of flaws.Just because some people are afraid to do this shouldn't stop you if you do some research

Re: Porting Stock e50 Cylinder?

Downhill Harvey (OFMC) /

Cleaning up casting flaws and porting a cylinder are two different things. If you have a few spare cylinders, then go for it.

Re: Porting Stock e50 Cylinder?

Better Fส็็็็็็็็็็็็็็็็ster /

Downhill Harvey Wrote:

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> I've never understood what makes a noob, with a

> dremmel, think that they can do better than the

> factory. Leave it or kit.

The factory purposely restricted the cylinders so that the bikes would stay at specified speed and hp ratings. There are lots of gains to be made from porting.

DISCLAIMER- read this whole post before you even think about touching a Dremel. There is a lot to learn, and I'm not responsible for any alterations you make to your motor.

Widen ports for more torque. Raise exhaust and lower intake for more rpm. You have to be careful with both. Too wide and you'll snag a ring or not seal up the intake. Too high on the exhaust and you won't have enough power to get to the higher revs. Too low on the intake and you'll have massive blow-back out of the carburetor. Porting is always a trade off between torque and high RPMs.

Here is the low-down on simple port jobs. I wouldn't do anything too extreme on your first port job. Stick to the basics. Remember: you can't put material back. It's cheaper to keep installing the cylinder and testing it than it is to buy a new one. If you really want to know what you're doing, I suggest reading up on port duration and port time area before you attempt this.

First, Identify whether or not you have a low torque or high torque cylinder. Low torques are stamped with a single digit number and high torques are stamped with a double digit number. The dimensions I have here will work for either, except intake heights and piston skirt trimming on high torque cylinders. Don't attempt to modify a high torque intake to these specs.

Low torque looks like this:

and high torque looks like this:

Ok, we'll start out by port matching. On the high torque cylinders, I usually find some pretty big problems where the cylinder lines up with the case. Make sure everything lines up before you decide to start changing your engine characteristics. I'm using a magnum #1 cylinder for a comparison because it uses the same stroke and bore and it's the only unported stock cylinder I have off a bike at the moment. It almost looks like a high torque cylinder, with the exception of having more fins and being stamped with a single digit number.

Remember that flowing fluids don't like sharp corners. You'll have higher rates of flow with smooth transitions and rounded corners. I also really suggest cutting on the black dotted line above. That should help your flow from the cases.

Next, make sure your intake and exhaust match. Make gaskets and match to them so that everything has smooth transitions.

Now you have some of the basic flaws out of the way, let's check out how to get more power out of that little engine. Let's start with the piston. With the cylinder installed, take off the intake and look into the intake port on the cylinder. With the piston all the way to the top of the cylinder, does the piston skirt still cover the intake slightly? It should if you have a low torque piston -with two square rings instead of one square and one "L" ring. If so, Check out the next pic. If not, skip that step.

I almost always cut the intake side of the piston skirt right where the machining marks are. By cutting the intake skirt here, you're making the intake open all the way and increasing your intake duration. For more low-end, cut this shorter. You can always cut more off, but don't go past the machining line. Also, don't cut the exhaust side of the skirt. It needs to be long in order to seal up the exhaust at the top of the stroke.

Finally, you have to alter the port map. Make sure to do a port map before you start porting. Check out this link for more on port mapping This was the port map that I started with.

The intake on this cylinder was already quite large. Some 1.5 hp bikes have smaller intakes than this and all 1 hp bikes do. This is a good shape for the intake. The top of the port is rounded and the intake has a huge area. Ideally, you only want to open the intake until the area is the same as the area of your carburetor and intake. Make sure to do some math and don't make it too big. Also, these intake heights are only valid for low-torque cylinders.

This is what I would do to change the port map.

We already modified the intake duration by cutting the piston. The transfer ports are too hard to modify without special equipment as the angle that the port enters the cylinder is very important. That only leaves the exhaust to be modified. The exhaust can safely be widened to 67% of the bore diameter or 25.46 mm before you run the risk of snagging a ring on the port. Make sure to leave the corners rounded so that the ring is eased in slowly. The more oval the port the better. You will also want to raise the port. I usually go up 5mm so that I have a port timing of 164 degrees -assuming a 1mm deck, which is common on these bikes. This will give power up to about 8.5k RPMs. Start with mm by mm increments though. DON'T do this all at once. When your bike gets close to where you like the amount of power, go up by smaller increments or stop. I sometimes go higher, but I have long straight aways where I live. I assume you're driving in stop and go traffic. If that's the case, 5mm may even be too much for you.

When you're done, chamfer the port edges where they meet the cylinder. You basically want to just knock off the sharp corner with a bit of sand paper or emery cloth. Make it look like in this picture that I stole off from another website:

Finally, before you install the cylinder on your bike, make sure to wash everything out thoroughly, then wash it all out again. Make sure that there aren't any specks of metal anywhere near your engine. One speck can easily mar a perfectly good cylinder. You don't want to destroy your cylinder after all of this hard work.

I'm sure I missed quite a bit, but I could really write a book on this. Also, if anyone wants to critique me, go for it. I've done quite a few of these, but I'm sure there's more than one way to skin a cylinder... or port a cat... I'm not good with there metaphors... Anyway, good luck. Hopefully this all makes sense. If not, ask questions. The wiki is also full of info. Check out Jennings' and Bell's books on two stroke performance tuning.

Again, if you have any questions, please feel free to ask.

-StronGAR

And for those of you who hate long posts:

TL;DR version: If you don't read this, don't pick up the Dremel. (edited)

Re: Porting Stock e50 Cylinder?

Sasha Alexander /

Oh very nice, thanks for that. Most pics aren't showing though can you repost them? Or feel free to email them to me fearfordeer@gmail.com I can post them here with my photobucket.

Re: Porting Stock e50 Cylinder?

Better Fส็็็็็็็็็็็็็็็็ster /

All of the pictures work on my end. Try opening it in chrome. I'll hyperlink to them anyway just in case my computer is playing tricks on me.

In order from first to last:

Low torque

High torque

Transfers

Intake

Piston

Port map 1

Port map 2

Chamfer

Potato

Re: Porting Stock e50 Cylinder?

woah 5 mm higher on the exhaust!?! thats pretty aggressive imo, beginners start at 1 mm or so and work your way up. by the time you've gone full boat anchor you'll know what to do next time!

Re: Porting Stock e50 Cylinder?

Graham Motzing Wrote:

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> woah 5 mm higher on the exhaust!?! thats pretty

> aggressive imo, beginners start at 1 mm or so and

> work your way up. by the time you've gone full

> boat anchor you'll know what to do next time!

"You went full boat anchor... Never go full boat anchor"

Re: Porting Stock e50 Cylinder?

'some things on this submarine do not react well to porting' (i just cant fake that sean connery accent well)

Re: Porting Stock e50 Cylinder?

Better Fส็็็็็็็็็็็็็็็็ster /

The stock exhaust port is 33mm from the top of the cylinder, which is a port timing of roughly 135 degrees. This produces power up to 6.5k rpm.

By raising it 5mm, you get a port timing of about 164 degrees, which is a very usable timing. This produces power up to 8.5k rpm. I did suggest going a little at a time, but 28 mm from the top of the bore isn't too extreme. You just don't want to go too much higher on a single speed bike. 26mm is where you start reaching boat anchor status.

Porting by itself usually doesn't give great gains, unless you do it in addition to adding a pipe. Since you stated that you're getting a new pipe, that should increase your low rpm power considerably. This porting with a proma circuit pipe will get you around 39 mph on 16/45 gearing with decent low end. Tune your clutch if you need more low end.

Re: Porting Stock e50 Cylinder?

ehhh, i dont agree with going that big, but everyone for themselves.

my 'annie' cylinder was ported about 3mm up for something in the high 150's.... 158 deg i think? Exhaust was widened out to about 60% bore. It was chopped a mm or 2 on the piston with a notch, widened and lowered on the intake.

bike was GPS at 47 mph with 14/45 gearing. 16mm drilled bing, shitty cobbled together pipe. it also got off the line faster than a lot of kitted bikes.

i dont think getting the duration that long on an exhaust for a stock cylinder gets you anywhere, at some point you run out of transfer flow and its a diminishing return.

If you're porting a huge transfer scooter cylinder or something, 160-170 degrees is great, if you're porting a dinky little moped jug with anemic transfers, those guidelines dont apply.

Re: Porting Stock e50 Cylinder?

i'd also like to know where you're coming up with the numbers of 135 degrees making power up to 6.5k and 164 making power to 8.5 k

Re: Porting Stock e50 Cylinder?

- Summerai - Drew /

Graham, corey and I built a hogged out 50 kstar and hit 50.4mph last night. 12 bing and a techno bullet!! massive transfers, maybe a little to large. Hey man, ill see you this weekend.

Re: Porting Stock e50 Cylinder?

sweet, way to go guys! 50/50 congrats! I might have an extra drilled bing floating around i could toss you sometime too.

Re: Porting Stock e50 Cylinder?

Downhill Harvey (OFMC) /

StronGar said,

I'm sure I missed quite a bit, but I could really write a book on this. Also, if anyone wants to critique me, go for it. I've done quite a few of these, but I'm sure there's more than one way to skin a cylinder... or port a cat... I'm not good with there metaphors... Anyway, good luck. Hopefully this all makes sense. If not, ask questions. The wiki is also full of info. Check out Jennings' and Bell's books on two stroke performance tuning.

That's why I said, "leave it or kit". For me, it's just too much work to port out a cylinder, unless you have unlimited time and cylinders to work with.

Re: Porting Stock e50 Cylinder?

Downhill Harvey Wrote:

-------------------------------------------------------

> For me, it's

> just too much work

I get that, but why you gotta hate?

blue is exhaust, red intake, purple is transfers.

this is my low torque, 2hp e50, i dont know more than that.

x axis is RPMs, the constants are the ideal values from the japs. (edited)

e50lotorq.png

Re: Porting Stock e50 Cylinder?

I'd gone a little over 3mm up and out on each side, intake down 2, widened out and matched to the 15 bing intake and cut piston skirt. 15x45, 15 bing, estoril and had it to 46.

thing drank gas tho, then i sold it.

i often though about it in the time following, and finally it came back with another new owner. the thing'd been ruined and replaced with a kstar and only managed to get 43...

Re: Porting Stock e50 Cylinder?

oh yeah and the stock blowdown I measured was about 22 degrees

Re: Porting Stock e50 Cylinder?

I just opened up my transfers to the size of the KStars to match my case. Didn't mess with the ramps. I also widened the exhaust and intake 3mm each. And raised the exhaust 2mm. I might consider lowering the intake. Gonna test it out this weekend, its going on a 19mm dell and a estoril.

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