piston mods

[stewart]

heres a piston cut away to un cover transfer port  big gain here[/img] read on rest of thread this is sample piston for looking at has to be cut to cover you exhuast transfers at tdc

[stewart]

notice shrouding of  front transfer port  by skirt bottem this piston has side toward you cut and side  facing down uncut  see the blockage of transfer port because of piston at bottem dead center when it needs open the most

[hangtime]

Why did the kawi engineers design the skirt that way? Does your cutout help bottom vs. top. And lastly, What is a transfer port?

[mg82]

when can i send you mine?

[stewart]

transfer ports are the 2 ports on each side of cylinder  this is a wiesco piston and you should look at your own to see how much it block front transfer at bottem dead center

[hangtime]

Does your cutout modify power delivery across the board, or is it more to a specific rpm range?

[stewart]

any thing that hinders flow cuts efficncy and velocty across the entire rpm range

[hangtime]

Where does the fuel go after the transfer ports? When people port cylinders, where do they grind to modify power delivery, bottom vs. top?

[KXcam22]

Stewart,
I did that exact mod on my '79 maico 400 that I raced.  Was combined with much other porting so hard to tell what its exact contribution was, but the combined effect was tremendous. From dog to holeshot heaven!!!  That is actually one of the porting things that make sense since as the piston travels downward, the cylinder transfer ports open up but if the skirt of the piston is shouding the lower transfer opening then flow is reduced unnecessarily. On my maico tje shrouding was terrible. Good pics.  I should mention that on my maico I had to cut away much of the reinforcement rib on the piston skirt which eventually caused to to crack. But it did last 50 races. That was a forged mahl piston, very strong.  Not sure how well the stock cast piston would last. I'll have to look at the ribs on my old one. Cam.

[YUNGGUNNAZ]

visualize the piston going at a rapid rate and you see how this area is actually being blocked.care should be taken how much,what angle(radius)on piston is done.stewart if i can find a box for pipe it'll be on the way.just got time to pull mine down before season.2 months behind.now i have to look for some more hp.competition may have seen this one.

[stewart]

do you race  against guys on kx 500 s   because the honda guys dont look here for tips they think there cr 500 is the perfect and the fastest bike possible so the info is safe

[YUNGGUNNAZ]

 the"i'm gonna kick your butt" came from a kx500 rider as well as 4 more kx's.they spend big bucks during off season.hope katie didn't see this.she was already fast. :-)more to it than hp though.pm the address again.wrote it down somewhere.try these 2 reed cages and pipe let me know the up or down.can't spend much time on dyno now.thks

[doordie]

This mods help cooling down pistontop and lubricate
little end bearing,a good mod for desertracing.
Even a better flow to inlet boostport.

[stewart]

be sure when cutting piston on this mod to put  piston it at tdc in the cylinder of bike  turn and look at bottem  and leave enough of skirt to cover exh booster ports at tdc which  will vary with each port job etc

[doordie]

be sure when cutting piston on this mod to put  piston it at tdc in the cylinder of bike  turn and look at bottem  and leave enough of skirt to cover exh booster ports at tdc which  will vary with each port job etc

tdc=TopDeadCenter
You don?t want to shortcircuit flow at TDC and it depends on what hight your barell is located and with different portduration(porttimes) you have.

Steward,what?s is "enough of skirt" to cover in your opinion?