Thread: Another porting question....
03-21-2009, 02:31 PM #1
Another porting question....
Everyone knows how the sleeve ports, and cylinder ports never match up from the factory. I need some input on this. If I match the ehxhaust port on the sleeve to the port on the cylinder, is this going to throw my exhaust timing way off? Have a look at the pic in full scale to see what I mean...
03-21-2009, 02:47 PM #2
You cannot just go in and start cutting without running the software.Moving the port up,down,side to side,even .005mm can take power away.If the port is not shaped right,you can stick a ring in no time.
03-21-2009, 03:01 PM #3
HINT/SECRET:.....send them to woody!! i did!!
03-21-2009, 04:09 PM #4
03-21-2009, 04:10 PM #5
03-21-2009, 04:13 PM #6
Your sleeves are you port timing.When your piston drops and opens the port, the diameter,shape of the sleeve is what determines the timing etc....The sleeve is smaller than the port itself.
03-21-2009, 04:18 PM #7
Woody... I understand the theory of how all of that works. I guess I will just put it together, and ride. Some of the 65U guys say the they can't even so much as hang a fingernail on their sleeves. The 64X is 2/3 of the 65U. That was my line of thinking.
03-21-2009, 04:20 PM #8
Thats cool JeepGuy,just trying to help you out.
03-22-2009, 09:22 AM #9
In your picture the part you were talking about cutting to match is timed for the exaust. Imagine the piston comeing down after combustion. The first opening to open up is the exaust.
If you removed the material you have marked in your pics then the port would be open sooner because the piston doesnt have to travel as far to get to the open window.
This reduces the time that the piston traps the combustion before reaching the open port and exausting the pressure out your pipes. The time after the port has opened is called blowdown time.
The more blowdown time you give the motor the more freespin it can attain at the expense of torque. This is why porting the exaust port lowers compression and allows for more rpm.
After porting this exaust your compression would be low so to bring it back to operating range you would then use a head recut to bring the compression back up.
The entire process moves the torque curve to a slightly higher rpm range. Thus giving the benifit of more power at higher rpms.
03-22-2009, 01:59 PM #10
On the 701 and 760 twin cylinders you cannot remove this part
of the sleeve (completely) and match it to the cylinder. You will be raising your port timing to much and your end result will be a motor that will
be so weak it will not be able to pull through the midrange area
5000 to 6000 rpms. Even after adding compression back it will be too great unless you added addition timing in this area to offset the issue. The
results would greatly effect octane requirements on your setup. What your doing is adding your HP curve to a lot higher rpm, which is ok, if
you correct your bottom end problem that you would have after the mod.
We learned this many years ago when the motors first came out in the
WaveRaiders and then later in the GP series.
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