KX Riders
Maintenance & Technical => KX500 Original => Topic started by: stewart on March 20, 2007, 01:31:50 PM
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heres a piston cut away to un cover transfer port big gain here(http://[img])[/img] read on rest of thread this is sample piston for looking at has to be cut to cover you exhuast transfers at tdc
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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
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Why did the kawi engineers design the skirt that way? Does your cutout help bottom vs. top. And lastly, What is a transfer port?
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when can i send you mine?
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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
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Does your cutout modify power delivery across the board, or is it more to a specific rpm range?
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any thing that hinders flow cuts efficncy and velocty across the entire rpm range
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Where does the fuel go after the transfer ports? When people port cylinders, where do they grind to modify power delivery, bottom vs. top?
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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.
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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. :-D
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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
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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
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This mods help cooling down pistontop and lubricate
little end bearing,a good mod for desertracing. :wink:
Even a better flow to inlet boostport. :evil:
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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
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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. :wink:
Steward,what?s is "enough of skirt" to cover in your opinion? :|
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yes doordie tdc = top dead center and each kx 500 piston needs the bottem cut to match exhaust booster and exh floor with probley .050 matrial covering exh port s at tdc looking but that can un shroud transfers at bdc by alot on most combos witch heps flow =horse power
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Oki,so you have to be very carefully with the radius of cutaway,so it?s still 0,05 left of skirt at TDC and doesn?t shortcircuit to Exhaust boostports?
No problem with cracks from the "new radius" of piston?
At uncut pistons,it?s thicker material round whole radius,but it doesn?t matter maybe? :|
The gain is more importent anyway :evil:
Steward and younggunnaz,we have to share every good mods so twostroke still rules! :-D :evil: 8-)
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the wiesco piston is the same thickness inthat area only stock cast piston has ribs at the border where you need to grind
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stewart
have you dyno this mod yet.
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you can thank kawasaki for that deal. no wiseco new piston doesnt fix that deal.
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i wouldnt waste alot of time on that deal for the kind of riding you do.
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if u remove any material from piston as shown in picture it will expose exhaust sub port at TDC(cant be good}. there is only about 1mm / .004 of piston skirt covering the exhaust and subports at TDC on a standard setup .5mm base gasket prox&other cast pistons
was recently trying to lower a barrel {more low down power} until Larry Wiechman warned me of the problem i could encounter with exposing the exhaust ports
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Motorrad well spotted with that one, the motor may run faster for a while as it will running lean, i think when kawasaki designed a racing piston they not add any unnessary weight or size anywhere ,except window mod which is common on loads of bikes kx250 etc
dont know what stewart was thinking with that first picture
,
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But when the powervalves are closed the subs aren't flowing. The subs are cut back to far too, they are into the wrist pin area. Thats another big problem for a midrange motor. You can run a skirt mod like that but it takes custom parts. There are alot of 2 stroke with the skirt blocking at bdc.
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hi there new to this site. i have read through a reasonable amount of threads on this site,moreso the enine tuning and modification
topics,i too am very dubiuos about this side skirt cut? i have a standard cylinder and piston etc and agree fully about the skirt obstruction at bdc,however if i were to cut the psiton to the degree suggested by stewart i would be freeporting at tdc BIG TIME as the ex subs are well exposed,with this engine i think even 1 mm off the skirt would be pondering on suspect? whats your opinion on this stewart?do you have measurements from cylinder deck to sub port floor for standard?its just i would likr to carry out this modifiaction however i really dont think it would be suitable on this engine,could you please shed some light or suggestion on this for us,thanks.. :?
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You are missunderstanding Stewards techtips,this piston were an example to show
how much area was covered at bdc.
You can remove "some" material at were he is pointing with blade.
Not the whole cut-out area at example piston....
I got some old used pistons with this mod,I will take a photo soon to show difference of stock and
modded.