Porting a 2 stroke head?

Mojavekid18

Mojavekid18

Well i have been reminded lately that this is a dirtbike forum where i can ask questions so i figured i'd give it a shot. :smirk:. Anyways I am going to try to attempt to do a very minor port and polish on the *cylinder and intake on the kx 125. I have watched a couple videos and get the basic concept, just wanted some educated thoughts/idea's on this. Have a couple questions too.

1. In the videos i watched he used the carbide bits to open up the *ports alot, i don't feel like i need to go that extreme. Could i just use a regular grinding bit if all im doing is cleaning up casting marks?

2. I have heard alot of theory about leaving intakes rough to atomize the fuel better. Anyone have any ACTUAL experience with both smooth and rough intake ports? (I will clean up the casting marks either way)

3. Should i bother getting a sanding wheel for the dremmel? They only go up to 120 grit and to polish i will have to do 220-1000 by hand anyways.

Any other advice is welcomed too!
 
jackson409

jackson409

Forgive me, not a master builder here but I didn't think the head on a smoker has anything to do with intake on the fuel system. I only thought the ports on the head were water ports. The intake was on the jug portion where the reeds reside?
 
Mojavekid18

Mojavekid18

jackson409:
Forgive me, not a master builder here but I didn't think the head on a smoker has anything to do with intake on the fuel system. I only thought the ports on the head were water ports. The intake was on the jug portion where the reeds reside?
Click to expand...
yes two strokes suck in air and fuel through the crankcase and up through the head. Thats what all the ports on the cylinder wall are for.
These are the intake ports (sorry i coulden't find a better picture) The water jackets run through the holes useally on the front or back of the cylinder
picture2.jpg
 
SRAD97750

SRAD97750

Moderator
Staff member
Are you looking for something that's missing from your current power delivery?
I suggest trying different base gasket thicknesses, as this will alter the 'port timing'. Port timing is related directly to the characteristics of the 'power band'.
As far as removing the casting marks, I don't see an issue. If you have two identical cylinders, I'd be interested in polishing one, and leaving the other stock and see what kind of instant differences you notice. :thinking: -BIG DAN
 
bobkyle2

bobkyle2

My cylinder is ported and polished, And base has been cut.... Makes powerband like a light switch, I don't really like it lol. I need a thicker gasket.
 
Mihylo33

Mihylo33

Porting and polishing will dramaticly increase the response of engine. Opening the bottom of the port will increase top end, opening the top end of the port will increase the low end grunt... polishing the ports increases the flow and allows more fuel to flow into the combustion chamber sooner. Peeople then cut the head to improve combustion efficiency and now comes the race gas.... I dont recommend doing this yourself unless you plan on replating the cylinder. You also wann match and polish the cases to get the most out of your engine...
 
jackson409

jackson409

I have also heard, if you don't do it perfectly, you will make your engine worse. From my understanding there are lines/rough/texture areas in the intake ports that are there for a specific reason to cause fuel disapation. You can polish the exhaust port to a mirror finish but the intake ports you want it textured.
 
Mojavekid18

Mojavekid18

Mihylo33:
Porting and polishing will dramaticly increase the response of engine. Opening the bottom of the port will increase top end, opening the top end of the port will increase the low end grunt... polishing the ports increases the flow and allows more fuel to flow into the combustion chamber sooner. Peeople then cut the head to improve combustion efficiency and now comes the race gas.... I dont recommend doing this yourself unless you plan on replating the cylinder. You also wann match and polish the cases to get the most out of your engine...
Click to expand...
would i have to run race gas even with just polishing the exhaust and then just getting rid of the casting marks for the intake? Im not port matching until i have enough money to get the other cylinder replated. And im not gonna be touching anywhere near the actual cylinder wall because i don't want to chip my nikasil

jackson409:
I have also heard, if you don't do it perfectly, you will make your engine worse. From my understanding there are lines/rough/texture areas in the intake ports that are there for a specific reason to cause fuel disapation. You can polish the exhaust port to a mirror finish but the intake ports you want it textured.
Click to expand...
Yeah this is one of the things i was wondering about. I don't think i will do anything but get rid of casting flaws on the intake for now.
 
Mihylo33

Mihylo33

Mojavekid18:
would i have to run race gas even with just polishing the exhaust and then just getting rid of the casting marks for the intake? Im not port matching until i have enough money to get the other cylinder replated. And im not gonna be touching anywhere near the actual cylinder wall because i don't want to chip my nikasil


Yeah this is one of the things i was wondering about. I don't think i will do anything but get rid of casting flaws on the intake for now.
Click to expand...


you wont have to run race gas if you just polish the flow channels... if you cut the head, or cut the ports then 95% of the time you usually have to run some type of race gas.... You want alot of bang for your money?? Match the cases and polish the flow

http://makestuffdostuff.blogspot.com/2010/09/case-matching-my-e50-puch-engine.html

your bike will get a significant power increase with this inexpensive mod.
 
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