Porting Stock Cylinder e50

I took apart my stock e50 cylinder to get a closer look at it with the intentions of port matching the intake and exhaust (its a 2hp cylinder). Things are pretty close, but there is a small amount of material that can be grinded away to get closer to a perfect match. One thing I noticed was that my intake was definitely smaller than the intake port on the cylinder, so I reamed out the intake a bit to match. The real question I have is regarding the intake and exhaust ports on the cylinder. When you look into the ports from the outside I could see a sort of ramp that seems to obstruct flow a little big. I don't know how to describe it, I just figured you guys more familiar with the stock setup will know what I'm talking about. I was thinking about drilling straight through the intake and exhaust port into the cylinder which would cut a little bit of that ramp out, but figured I better consult the wiser ones before I make such a hasty move. How do you guys modify your stock cylinders ? I'm specifically curious about the material inside the cylinder that seems to ramp out in front of the intake window and exhaust...Do you cut into that to increase flow ?

Re: Porting Stock Cylinder e50

Overpriced Parts /

Search wiki for porting info.

When your done porting drill a half inch hole through the fins to attach the 75' marine rope to.

Re: Porting Stock Cylinder e50

already got an anchor for my boat, thanks.

Re: Porting Stock Cylinder e50


read a bunch of stuff first.

that is all.

Re: Porting Stock Cylinder e50

Ok, no drilling. But I'm still curious for my own knowledge sake. Why doesn't the intake port open straight into the cylinder ? When I look into the intake I can see the fuel doesn't have a straight shot into the cylinder. What's the reason for that ?

Re: Porting Stock Cylinder e50

drill some auxiliary exhaust ports!

Re: Porting Stock Cylinder e50

it's ramped like that because the fresh charge doesn't actually go into the combustion chamber, it goes to the cases first and then up through the transfers

Re: Porting Stock Cylinder e50

Jeremy Freeze Wrote:


> drill some auxiliary exhaust ports!

I wonder what would happen if you made 2 more Exhaust mounts? higher compression?

Re: Porting Stock Cylinder e50

Simon Nyi Wrote:


> it's ramped like that because the fresh charge

> doesn't actually go into the combustion chamber,

> it goes to the cases first and then up through the

> transfers


If you want to try porting widen the exhaust 2mm on each side and raise it about 1mm. Raise and widen the intake about 1mm (top and sides). Use a marker or tape to mark off where exactly you are going to cut. Then clean up any shitty edges with a file.

Good luck, dude.

Re: Porting Stock Cylinder e50

Usually first thing is port matching. What I'll do is line up everything, put the piston in properly oriented in the cylinder in hand, and line up the top of the piston with the bottom of the exhaust port - this is BDC. Then mark off the piston and the cylinder skirt mismatches and make them match. Same with anymismatch on the cylinder from the case (use base gasket as a guide - some stock puch aren't fully cut, "devilhorns")

Then take your intake and exhaust that you plan on using and their gaskets, make sure the gasket diameters match and then use the gaskets as a template to match the intake diameter and exhaust diameter on the cylinder.

Next would be port timing, which has alotta gains to be made but it's also easier to do irreparable damage. If you wanna do it right read the wiki on calculating port timing. I've had success with as aggressive as 175exhaust and 25 blowdown with 150 intake. but you gotta tune the clutch to accompany that...

OR more simply just follow a tried and true simplified port alteration like chris laid down. 2mm wider oval exhaust, raise 1 (never over 2mm), and lower the intake the same amount (i.e. 1mm) and you can widen it but it probably won't make much difference with a small intake&carb.

and yea chamfer everything smooth inside the bore. some people polish the exhaust shiny, that's kinda worthless on most bikes tho, especially 2t where it's gonna get messy pretty quick anyway


Re: Porting Stock Cylinder e50

If you want to experience aggressive puch piston port timing then buy a TCCD 50 cc aftermarket cylinder. You can port a stock cylinder similarly but it will be beyond Chris' formula. The 'Chris' formula is your best bet for now anyway. Make a intake with a gradual bend instead of the stock 90 degree bend for much better high rpm.

Re: Porting Stock Cylinder e50

Thank you. I've port matched everything, chamfered and put everything back together. I wanted to give it a ride and see how I did before diving into port timing without testing the results of my port match job. Definitely a small, but noticeable increase in performance ! Pretty cool. I'm gonna ride it around a bit before I take it apart again and try the widen and raise method. Treats just got blue springs in and I've been waiting for it because I want to tune my clutch. Once that project is finished I'm going back into the cylinder to change the timing a bit.

Re: Porting Stock Cylinder e50

If you don't know already, port timing on a 50cc singlespeed is a balance between max rpm achievable and how much torque you are willing to give up. My personal experience is that you can mill the head a lot to get as much as a 215 psi compression reading using premium gas to recoup some torque without blowing it up if it is tuned right. A large pipe like a Homoet 6P will really help too

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