trying to understand port timing

[lms1977]

I check mine last night and here is what I got it was slightly ported before.

 

184 on exhaust

120 on transfers

112 on the boost port above the intakes

if I'm correct that would be 32 blowdown

 

from what I have read a 188 exh and 128 transfers with a 30 blow down seems it would be a good all around motor.

 

these are cylinders that are .08 over so I'm going to play with them if I wreck them it won't be the end of the world and I do have access to the right angle tools to do the transfers.

 

Any input would be appreciated

[Larry's Shee]

You keeping rest of mods same??

[RadarRacing]

Blowdown is the difference in degrees of crank rotation from when the exhaust port opens till when the transfers open. 188/128 would not have as much topend HP. 185/115 is stock so I don't know if your exhaust is even raised depending on how you measured. To answer your question port timing is the amount of crankshaft rotation in degrees that a port is open. If you want help with your setup you need to give more info about what type of motor you are wanting, drag,MX,dune, pipes, etc.

[RadarRacing]

Sorry I read it wrong. It now has 188 and 120? For MX or woods riding I wouldn't change a thing. Do NOT raise the transfers to 128 with that low an exhaust port. 128 and about 194-200 would be drag timing numbers and suck balls to woods or MX ride.

[lms1977]

You keeping rest of mods same??

For now anyway.

[Pasi S.]

I check mine last night and here is what I got it was slightly ported before.

 

184 on exhaust

120 on transfers

112 on the boost port above the intakes

if I'm correct that would be 32 blowdown

 

from what I have read a 188 exh and 128 transfers with a 30 blow down seems it would be a good all around motor.

 

these are cylinders that are .08 over so I'm going to play with them if I wreck them it won't be the end of the world and I do have access to the right angle tools to do the transfers.

 

Any input would be appreciated

 

 

Remember that I am not a professional on this one or anything.

I did my porting by myself and it was hard. I´m happy now because it´s done. I can´t tell how it is, because it is still apart.

 

They say, that if you want to save some low end power, don´t go over 190 exhaust.

They also say, that if you want to keep your mid-range, don´t go over 196 exhaust.

They also say, that BD close to 30 can keep your low end happy, and BD close to 35 is for top end power. Everything between is between.

 

I have "drag" numbers in my stock cylinders, but my porting is not a drag port. Shapes, angles and time areas makes a difference.

 

-Pas S.