What to remove while porting??

[Carl Walichnowski]

So I've decided to do some porting on my own and looking at different threads and sites I've read numerous suggestions on what should be taken off. One thread said "I opened the intake ports sides by 1.5mm a side and lowered the floor by 1.75mm." I have a 66cc Grubee Skyhawk and I wondered if this would be correct
I thought that the measurements would be specific to the model of engine you have, if so is there an easy way to determine what should be removed. I'm very much a noob who's trying porting for the first time so if anyone has any helpful links for videos that'd be appreciated.

 

[Will'smotobikes19]

Well the thing is to not take off too much its not exactly a science and to match the exhaust port with the pipe opening so the exhaust gasses flow better. The porting should be smooth too possibly even polished with several grits of sandpaper on the exhaust. Some people say to leave the intake rough so the fuel atomizes better. I've never done it myself. I just got a 48mm iron sleeved cylinder and stroker crank. The iron sleeves last longer than chrome lined and its a whole milimeter bigger bore which is about 70cc.

 

[INTP_ty]

Skip it. It’ll run smoother

 

[Deleted member 12676]

you can widen the intake, lower the intake, and raise the exhaust port for more power and higher RPM
but if you haven't balanced the crank then you're in for a whole lot more vibration.

 

[Will'smotobikes19]

I think trimming the piston skirt helps too.

 

[Carl Walichnowski]

Well the thing is to not take off too much its not exactly a science and to match the exhaust port with the pipe opening so the exhaust gasses flow better. The porting should be smooth too possibly even polished with several grits of sandpaper on the exhaust. Some people say to leave the intake rough so the fuel atomizes better. I've never done it myself. I just got a 48mm iron sleeved cylinder and stroker crank. The iron sleeves last longer than chrome lined and its a whole milimeter bigger bore which is about 70cc.

Where did you purchase the 48mm iron sleeved cylinder and stroker crank?? It general increases the life of the motor correct? Any other added benifits?

 

[Will'smotobikes19]

From mzparts miami on ebay the jug is $100 and the crank is $50. The iron sleeve will increase engine life and its 48mm instead of the stock 47mm bore which will give more power. Especially with the stroker crank and flat top piston. You could probably do a top end rebuild too without having to buy a new cylinder. >Update the cylinder came in the mail. The piston isn't a flat top though. Some scratches on the piston too.

 

[Deleted member 12676]

Lacking here is the matching of ring type to cylinder type.
The rings have to match the cylinder or they wear quickly.
If the stock rings are made to match a chrome lined cylinder then they will wear too fast on an iron lined cylinder.
Too often little but important details like these are overlooked by sellers in their rush to make a buck.

 

[Will'smotobikes19]

I heard you're supposed to lap the rings to get rid of burs. On a iron lined cylinder top end rebuilds could be done and the rings are probably pretty cheap. I got my package they included what looks like a 47mm low hole with a window in it but the bore is 48mm.

 

[Rick73]

so let's say I want to port my head and shave my piston to match the ported head. so after I take out the piston and cut off what I needed to when I put the piston back in do I have to replace the piston rings and break in my engine again or can I use the same piston rings that I have that are already in use?