exhaust port trouble

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Aug 6, 2001
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#1
:think

I have a 98 KX 125 that I just had resleeved. when I was putting it back together I noticed that there is an eighth of an inch difference between the exhaust flange and the cylinder. the port where it meets the flange on the outside of the cylinder. There is not a smooth transition between them. should I take my dremel and make it a smooth transition? if I do will it increase the power or is it a waste of time? also what mixture should I use for break-in?
 
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Mar 22, 2001
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#2
do grind it down. also, check the other ports. if they don't line up, grind them too.you might need the right angle attachment. i would recommend just running 32-40:1 just go easy, and take off the pipe and inspect the piston before you go crazy on it. (i don't recommend grinding your sleeve with the cylinder installed.)
 
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#3
Port window misalignment is a common problem with sleeves, and is one of the reasons sleeving is such a poor way to repair a cylinder. The problem is that you don't know whether the window is in the correct position in relation to the crank or not, so unless you have the expertise to measure the port timing, grinding the ducts to align them with the windows is just a crap shoot at best. If there are bad misalignments, I would take it somewhere that has the tools and expertise to measure the timing and area of all the ports, and if they are not within factory specs, I would have the company that sleeved the cylinder either resleeve it or replace it at their expense.
 
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#4
the flange that I am talking about is the the one that the pipe fits into. the jug and the flange are two pieces. right where they fit together is where they are different . the outside circumference on the jug is smaller. Should all of the intake ports on the sleeve line up top to bottom. all of the ports line up at the top and on the sides, but not at the bottom.
 
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#5
According to Eric, that lip inside the exhaust port is there to help time the pressure waves, and grinding it down smooth will hurt the performance pretty drastically.

As for the port window alignment, the tops and sides are the critical areas for alignment. You should be fine.