Piston size 72mm????HELP!

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seanalex538
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Piston size 72mm????HELP!

Post by seanalex538 »

hey guys today i took apart my bike to replace the piston and turns out it has a 72mm piston in it! What's going on??
seanalex538
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Re: Piston size 72mm????HELP!

Post by seanalex538 »

I've been doing some reading and see that it has a 240cc big bore kit. Where can i get a replacement piston??

thanks
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Gotanubike
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Piston size 72mm????HELP!

Post by Gotanubike »

66mm is the standard bore size for the 200 and 69mm for the 220. Largest wiseco offers is a +1.0mm 70mm piston for the 220 and +2.0mm 68mm for the 200.

So I assume the bike is running without power valves then. Does it have any bottom end power?
1990 KDX200
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diymirage
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Re: Piston size 72mm????HELP!

Post by diymirage »

contact Eric Gorr at forward motion
he is the one who came up with this set up and he should be able to help you find a piston for it

http://www.eric-gorr.com/bbmasterlist.php

(for some reason he only has the 225 and 255 kits listed, might be a typo on the latter)



since the stock size is 66 and you are 6 MM over that I don't see why it wouldn't have powervalves?
all it takes is 3 MM of off the main valve to get proper clearance no?
newbbewb wrote:DIYmirage has it right.


-1996 KDX 200 woods weapon (converted to 99 green body)
-1996 KDX 200 plated street toy (barney edition)
-2003 Yamaha TTR125-L (wifeys bike)
-1997 KDX 220 project bike
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Gotanubike
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Piston size 72mm????HELP!

Post by Gotanubike »

Probably depends on which series/model it is. If I remember correctly Jason said that no bore is possible on the E series without removing the KIPS. With removed KIPS can be bored to 240cc.
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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diymirage
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Re: Piston size 72mm????HELP!

Post by diymirage »

could be, but I don't see why ?

if memory serves me well I have a 2 MM overbore in one of my KDX 200s and that did require a recutting of the main power valve
the good people at wiseco were kind enough to include instructions on tolerances with their 68MM piston
newbbewb wrote:DIYmirage has it right.


-1996 KDX 200 woods weapon (converted to 99 green body)
-1996 KDX 200 plated street toy (barney edition)
-2003 Yamaha TTR125-L (wifeys bike)
-1997 KDX 220 project bike
seanalex538
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Re: Piston size 72mm????HELP!

Post by seanalex538 »

I had a closer look at the piston and it says: A75F9 on the top and in the middle says 8003 72.20mm. It has a W on the piston and it's forged so it leads me to beleive its a wiseco forged piston.
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Piston size 72mm????HELP!

Post by Dodger »

Try Kustom Kraft for a piston - they do 240 kits for the KDX.

http://kustom-kraft.com/KAWASAKIKITS.html

Cheers.
I may be old, I may be slow, but hey I'm still getting my leg over - a dirt bike!
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Piston size 72mm????HELP!

Post by KDXGarage »

Gotanubike wrote:Probably depends on which series/model it is. If I remember correctly Jason said that no bore is possible on the E series without removing the KIPS. With removed KIPS can be bored to 240cc.
I spoke with Eric Gorr years ago on it.
Thank you for participating on kdxrider.net. :bravo:
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diymirage
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Piston size 72mm????HELP!

Post by diymirage »

Jason wrote:
Gotanubike wrote:Probably depends on which series/model it is. If I remember correctly Jason said that no bore is possible on the E series without removing the KIPS. With removed KIPS can be bored to 240cc.
I spoke with Eric Gorr years ago on it.

good enough for me then, I still don't understand it, but i'll accept it :?
newbbewb wrote:DIYmirage has it right.


-1996 KDX 200 woods weapon (converted to 99 green body)
-1996 KDX 200 plated street toy (barney edition)
-2003 Yamaha TTR125-L (wifeys bike)
-1997 KDX 220 project bike
seanalex538
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Re: Piston size 72mm????HELP!

Post by seanalex538 »

Mine's a 1993 kdx240 and the KIPS system still works. I read that their is a mod that makes them useable with the big bore kit and i'm guessing i have that mod done to my cylinder.
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Gotanubike
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Piston size 72mm????HELP!

Post by Gotanubike »

WOW that's crazy....there is only about 2mm of cylinder wall behind the center valve. Any boring would surely clear out that part, leaving about a dime's diameter worth removed from above the main exhaust port.

I'm guessing a good portion of the larger displacement is through the stroke..
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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Julien D
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Re: Piston size 72mm????HELP!

Post by Julien D »

My understanding of the 240 kit on an E series is that you can keep the subvalves, but lose the center. Perhaps different shops have different methods, I don't know.
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Gotanubike
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Piston size 72mm????HELP!

Post by Gotanubike »

seanalex538, any chance you could post a few pics of your cylinder bore?
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
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Re: Piston size 72mm????HELP!

Post by KDXGarage »

It has been 8 or 9 years since I called and asked him. I do remember something about (not enough material) or something like that.

One possible big bore option for the 1994 KDX is.....WAIT FOR IT.........






































































Image
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
seanalex538
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Re: Piston size 72mm????HELP!

Post by seanalex538 »

Hey guys,
My local machine shop can get Wossner pistons!!
I'm getting a 73mm forged piston with wristpin, c-clips, rings, for 150$ shipped!! :grin:
And how do you post pics???
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Gotanubike
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Piston size 72mm????HELP!

Post by Gotanubike »

Upload to a image host like photobucket.com and copy and paste the .jpg it gives you
1990 KDX200
Bike Profile -> http://www.kdxrider.net/forums/viewtopi ... 61#p136315
Suspension Overhaul(Shock+89-92 conventional forks) -> http://www.kdxrider.net/forums/viewtopi ... 15&t=15255
96'-98' RM125 Showa 49mm fork swap -> http://www.kdxrider.net/forums/viewtopi ... 04&t=16994
KDXrider world map! -> https://www.zeemaps.com/map?group=186158
seanalex538
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Re: Piston size 72mm????HELP!

Post by seanalex538 »

Theres a couple pics of the piston. The cylinder is at the machine shop right now but when i get it back i'll post pics
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Re: Piston size 72mm????HELP!

Post by Erik225 »

Seanalex538 i know this was a while ago but what did you ever find out about that 72mm piston because i just got one with a 71.95mm piston and cant figure it out
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