porting transfer tunels

[zekibanshee]

How much can you grind out of the transfer tunels,if you have 65.25 bore. What i have read thats the part were banshees are choke, cylinders already have a mild port done ,but transfers were not touch that much. I have read that the more bore you have the more you can grind out.

Edited November 5, 2010 by zekibanshee

[midlifecrisis]

I know nothing about porting a cylinder, but I do know that there are guys on here who specialize in those sorts of practices. Dont chance screwing up your cylinders by experimenting with them. Send them to someone who knows how. JMO!

[jbooker82]

Yep porting a 2 stroke isnt just about incresing flow like a 4 stroke head. They make the ports larger. This makes the ports open sooner. Porting a 2 stroke is like putting performance cam in a 4 stroke. You changine when the exhaust goes out and the fresh fuel and air come in. I woudn't try welding up a cam and regrinding it so I wouldn't try doing a 2 stroke port job.

[AKheathen]

yah, the transfers are real important not to screw up. you can stand to loose a large amount of power. first you have to put it on a degree wheel, then you have to match the degrees of rotatoin to have proper blow-down, and time/area, then shape, angle, and velocity.......if you cannot calculate and figure all these things, then it's better to leave it stock, other than mabey casting flaws....but don't change the shape, even the "hook" ridge in the opening. if you have "mild" porting already, then the exhaust time area is probably small enough that there is very little that stock transfers need touched, and you probably wouldn't notice the difference anyways.

[zekibanshee]

yah, the transfers are real important not to screw up. you can stand to loose a large amount of power. first you have to put it on a degree wheel, then you have to match the degrees of rotatoin to have proper blow-down, and time/area, then shape, angle, and velocity.......if you cannot calculate and figure all these things, then it's better to leave it stock, other than mabey casting flaws....but don't change the shape, even the "hook" ridge in the opening. if you have "mild" porting already, then the exhaust time area is probably small enough that there is very little that stock transfers need touched, and you probably wouldn't notice the difference anyways.

I,m not talking were they exit into the cylinders I,m talking about the tunels on the bottom

[jbooker82]

If you make the ports to big you can hurt flow too. Large port with a low velocity.

 

Do what ever you want to.

[midlifecrisis]

See thats exactly what Im talking about. The fact that you have to ask about them in the first place screams to me "use a professional ! Im not trying to be a dick, Im just saying that the cylinders as a whole are pretty important, if you want to experiment, try maybe porting your reed cages or something, something more simple. Leave the technical jargin to these guys. Youve got 2 well respected veterans, and then me telling you the same thing.

[06specialedition]

I personally leave all my porting needs to an expert. You screw up those transfers at all, and you can hurt your bikes performance....just my opinion tho.

[stroking]

 if your talking about down here...i opened up mine alot and gained nothing but POWER all across the board..my case matches the cylinder also

 

Edited November 7, 2010 by stroking

[stroking]

i did NOT touch the tranfer windows at all though....only tunnel,intake,and exhaust

[AKheathen]

did you do it all at once? the biggest bump is in the exhaust. if you did not run it both before and after touching just the transfers, then that's a real biased result. looks like all you did was increase case volume, and lower velocity. you can smooth out flow some, but the more you try to let it flow, the more all the porting has to move gas, in order to keep up with the velocity, and pressure

[jbooker82]

did you do it all at once? the biggest bump is in the exhaust. if you did not run it both before and after touching just the transfers, then that's a real biased result. looks like all you did was increase case volume, and lower velocity. you can smooth out flow some, but the more you try to let it flow, the more all the porting has to move gas, in order to keep up with the velocity, and pressure

 

Two steps forward by doing the exhaust, and one step back by opening up the transfers to far. That is neat how you opened the ports up past the bottom of the skirt. That does nothing for flow other than reduce it. Lower velocity will allow fuel to fall out of the air streem as well.

[stroking]

Two steps forward by doing the exhaust, and one step back by opening up the transfers to far. That is neat how you opened the ports up past the bottom of the skirt. That does nothing for flow other than reduce it. Lower velocity will allow fuel to fall out of the air streem as well.

 

have you ever seen a cubs tranfer tunnels ?

 

 

 

 

 

there HUGE so i think it hurts nothing

 

some builders make the tunnels so big they have to weld up the outside of the cylinder

Edited November 8, 2010 by stroking

[jbooker82]

They dont grind them forward past the sleeve opening / bottom of the sleeve.

[AKheathen]

have you ever seen a cubs tranfer tunnels ?

 

 

 

 

 

there HUGE so i think it hurts nothing

 

some builders make the tunnels so big they have to weld up the outside of the cylinder

um....this is where it comes into play that the total flow of the cylinders needs to keep up. on a kitty jug, the time/area of the tripple exhaust, and large bore can call for such flow...especially with drag porting. just a "clean-up" isn't gonna flow like that. it's like people trying to pull low-end torque out of a 750 and rpm, or tunnel ram intake bolted to a stock sb350.......it just doesn't work that way, in fact, i can make the stock intake and carb blow that setup out of the water....even 2bbl.......and it's not from just hoggin it out..

 

so....figure out the angles and port/time and durrations, and then you can drag port that will like larger transfers, and better yet, stroke it while you are at it