piston window

[bige]

getting ready to do a top end 03 500 and going to do all the mods listed in this site power valve, cyl clean up etc. i was wondering about a window on my weisco piston, the stock piston doesnt have a window either so what are the bennifits of a window and how to cut one in if it makes a big improvement in hp.i already plan to put a 45 degree champher on botton edge of piston skirts so more lubrication will be forced between the piston and cyl wall. has anybody done a window piston in a 500?

[DoldGuy]

getting ready to do a top end 03 500 and going to do all the mods listed in this site power valve, cyl clean up etc. i was wondering about a window on my weisco piston, the stock piston doesnt have a window either so what are the bennifits of a window and how to cut one in if it makes a big improvement in hp.i already plan to put a 45 degree champher on botton edge of piston skirts so more lubrication will be forced between the piston and cyl wall. has anybody done a window piston in a 500?

Your answer is here:

http://www.kxriders.com/forums/index.php?action=search

DoldGuy 

[wierdo]

I had cut my own window from the info on this site, on both standard cast and a wisco and all went well. about 2 months ago i went to see Stephen who owns "The Two Stroke Shop" here in Australia,( check out the web site) and was warmly greeted and shown around his workshop. During the show and tell i asked all kinds of questions one of them being about piston windows size and positioning, he pulled out a banshee piston and a 125 piston of some model i cant remember and they were virtually the same in size and shape( both had small holes but in multiples, ie if the main intake port had 3 sections then there was 3 small windows in the piston) . He then told me that it is unimportant the size and shape, but a window is essential to all 2 strokes. 

[DoldGuy]

I had cut my own window from the info on this site, on both standard cast and a wisco and all went well. about 2 months ago i went to see Stephen who owns "The Two Stroke Shop" here in Australia,( check out the web site) and was warmly greeted and shown around his workshop. During the show and tell i asked all kinds of questions one of them being about piston windows size and positioning, he pulled out a banshee piston and a 125 piston of some model i cant remember and they were virtually the same in size and shape( both had small holes but in multiples, ie if the main intake port had 3 sections then there was 3 small windows in the piston) . He then told me that it is unimportant the size and shape, but a window is essential to all 2 strokes. 

I do not know Steve, have not talked with Steve or have had any business dealings with him, so use the info as you will.

http://www.rzrd500.com/phpBB2/viewtopic.php?t=7287

[wierdo]

Hows it goin Doldguy, Steve was a race engineer for Wayne Gardiner back in the day of the mighty 500 2 strokes, this guy knows what he is talking about when it comes to 2 strokes. He showed me an all new banshee motor that he has his own conversion for, to turn a 350 banshee into a 500 twin motor that converts a 250 aprillia pussy cat into a  road registered 500 GP, and also has plans for the same motor to go into a KTM motard. He's also looking at making his own heads with fuel injection. I love the way this guy thinks. I tried my hardest to persuade him to rebuild my k5 motor, even left it with him for a week hoping he would do it for me, but he's just so flat out with his road bikes. He was a real gentleman about it all and recomended a couple of other people and even dropped the motor of to the guy that is doing it for me now. I'm looking forward to going back soon just to see what he's been up to.

[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 
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 
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.

[wierdo]

Gday Bige it took me by surprise too, anyway have alook at this link
http://www.kxriders.com/forums/index.php/topic,3158.0.html

wierdo..

[bige]

thanks for the link thats what i was looking for. going to get the drill bit out and start cutting.

[kwakman]

use your inlet port as a guide to size and positioning.(86-88 or 89 on).as mentioned, you will pick up power, but little end lube and cool piston crown is the biggest plus.K.