KDX220 piston

Dapper

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Jan 25, 2002
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#1
I've read many post on the cracking piston skirt on the 220. My question is if this have been such a big problem why hasn't the factory upgraded the stock piston? I can't believe it would have cost them that much. Also it seems like that would be reason for the factory to have a recall. Just wondering because I have not changed out my piston yet but, have been thinking about it.
I have a 02 KDX220R :thumb:
 
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Oct 13, 1999
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#2
The piston only becomes a problem with a modified KDX. So there really is no problem with the way the factory makes them... as long as you keep them that way ;)
 

canyncarvr

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#3
That's true....except for the essentially stock 220s that have blown up, too.

No, not a lot. But it's happened.

Why don't they? Other than being cheap, I don't know.
 
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#4
I've got a 99 220, and I changed to weisco after 3yrs when stock piston was worn to spec limit. Per Dr. KDX, Jeff Fredette, piston failure is a hit or miss propositon....Some fail some don't....You may want to swap out to weisco at end of year....call FRP, I got everything for like 145. including tpend bearing, in about 4days. Good luck with it.
 

canyncarvr

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#5
Yeah. The problem is a 'hit' may end up costing you mega-hundreds of bucks.


I don't understand any argument about this. It happens......sometimes. It's been known to happen to any 220, regardless of modification. More often the higher state of modification? Yeah. NEVER to an unmodified or bolt-on modified bike? No.

Hearing from ten riders, 'It hasn't happened to me, therefore it's not a problem,' is stoopid.

If it happens to YOU, it has happened 100% of the time...to you.
 

canyncarvr

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#7
I was thinking of you when I said that :(

Thanks for chiming in!!
 
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#8
The reason that it's a "hit or miss" thing relates directly to the cause. Look inside one [better yet two for comparison] of the OEM pistons and closely examine the area around the transfer window. there are shrink marks and all kinds of casting irregularities in that area --and these vary from piston to piston. You'll find the same situation with the clutch hub & basket --and a friend's inner clutch hub recently cracked around one of these imperfections. In engineering terms these sharp edged areas create ACUTE ANGLES where stress becomes infinite and the metal fails. If one were to grind & polish those areas - eliminating the imperfections - you could probably use the OEM piston without any worry. IN the "old days" we used to polish con rods to prevent them from breaking. Get caught polishing your rod now they'd haul you in for indecent exposure.