Maintenance & Technical > KX500 Original

piston window

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sandblaster:
The size of a piston window does not matter but is essential?
I am not a engine guru by any means and I am trying to figure out these seemingly conflicting statements.
So please help me out.
As I understand it a two stroke piston does a few different things.
The top side of the piston compresses the fuel/air mixture and captures the energy created by the ignition of the fuel/air mixture.
The bottom of the piston creates a vacuum that draws the fuel/air mixture through the carburetor and reed valve and it pressurizes the crankcases to force the fuel/air mixture into the combustion chamber.
While the top and bottom of the piston are performing those functions the sides of the piston are exposing  and closing off the exhaust and intake ports like a valve does on a 4t engine.
I'm sure there are other things it is doing but that is the basics as I understand it.
To my way of thinking any changes to the piston will have an effect on the engine performance.
If a piston window size or shape makes no difference why not simply drill a small 1/8" hole in the side and call it good?
Because there are differences in cooling, fuel/air flow, ect.
I'm guessing that Steve was probably inferring that many different sizes and shapes will work just fine for the average engine.
But I find it hard to believe there is not some sweet spot for the K5 engine.
Am I right or am I all washed up?

wierdo:
Firstly, i want to apologise to bige for hijacking his thread. Sorry mate.
Secondly, Doldguy i have only just read your thread to the rzrd 500 forum and was unaware of all this past bulls**t which is irrelevant to this post anyway ( sounds a bit like the Stewart saga) . the point i thought i was making was that a windowed piston was a really good reliability mod not a HP gaining mod, and upon further research i could see that every manufacturer had the're own individual designs, some way different to what has been posted on this site but all work after all it was on this forum that i  first found out about it. And in fact Steve only confimed what was being said here on this forum.
Thirdly, hows it goin Sandblaster? I'm no guru either so i tend to listen to peoples opinions and ideas. I'm confused, where is the conflict? We were talking about putting a window in a piston. Do you use a windowed piston? what design have you used? obviously a 1/8 hole is going to do very little as would a gaping great hole would. As for a sweet spot I rely on the experts of this forum to show me where it is, and as i stated in my first respose to Bige, i have tried it on both the kwaka standard cast piston ( that had done quite a few hours ) and a brand new wisco, both working just fine. remember this is not intended as a HP mod. although if lowers the crown temp of the piston then its has to be good for a fraction of a HP as well as making the motor more reliable. 

sandblaster:
Hi Wierdo.
Firstl, I also want to apologize to bige for hijacking his thread.
Things are rolling along.
Nothing exciting happening, just paying the bills  :-o
I guess the statement that had me confused was "He then told me that it is unimportant the size and shape, but a window is essential to all 2 strokes."
I was just pondering out loud what he really meant.
Perhaps I'm taking the statement to literal?
Currently I run a standard Wiseco but my next piston will be a Kawrider windowed piston  :-D
I have to get a little ahead of this stagnant economy before I put any more effort into my toys  :-(

wierdo:
Hey Sandblaster,  Sorry, i keep forgetting that i also take things literally. I take that long when writing on here so i dont come across as a jibbering idiot, but the end result usally ends up the same anyway.
The point he was making to me was that a windowed piston is better than one thats not ,the shape is not that important which is confirmed by the various size and shapes that are being used by the various manufacturers.
Its a mod that us mugs in the bush wouldn't be able to tell the difference with the seat of our pants, as stated its for reliability, something that i have to rate as number one for me as the next closest town to me is 800 ks on a rough and dangerous dirt track( water buffaloes to dodge and big crocs at the river crossings) and the nearest city is another 300ks. This is also why i  only ride a 2 stroke and not a 4s.
I pulled out the old flogged out kwaka piston cut in window, chamfered the skirt, cut away the skirt where it shrouds the transfers and installed back into the motor and then tried to kill it but after 6 months of hard graft i was satisfied with the mods done and got a new wisco and did the same with the same results.
All up 1 days work and a well worth while mod that will not cost you anything if do what i did.
Merry Christmas all. Keep  roostin...WOT...

bige:
man i didnt think this would get so much responce, i guess a window is for more lubrication only, you would think all pistons would already have a window cut in them. i got a weisco piston to put in and have champhered the skirts 45 degrees all around to get more lubrication between piston and cyl wall. can any one give me the demisions to cut one in my piston before i install it? i want all the lubrication i can get.

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