Top End Rebuild

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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RodneyF2021
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Top End Rebuild

Post by RodneyF2021 »

Following sound advice on multiple forums, I decided to tear down the top end of my 2001 KDX 220R. Look what I found on the piston. Can you say 3 major cracks? Wow. Major disaster avoided.

After the rebuild is complete, how long would I expect the wiseco piston to last between rebuilds in terms of hours? What's the average time between rebuilds on the KDX 220 top end?
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Slick_Nick
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Re: Top End Rebuild

Post by Slick_Nick »

50 hours is a good benchmark.

That thing was ready to grenade. Good thing you took heed of the advice!
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Re: Top End Rebuild

Post by KDXGarage »

Run about any piston for way too long and it will look like that.

You might want to (if you have the fancy, high dollar tools to do it yourself) check for oblong wear in the cylinder / egg shaped / etc. or take it to a machine shop to have it measured. A piston can slap around for a while wearing out the cylinder.

I don't know how many hours are on that piston, but it was installed in the summer of 2000, so it has had its time. I would not suggest letting a new piston go for that long. :-)

For my putt putt self, I would do 50 hours on rings and 100 on a piston. The more you twist that throttle, the sooner the maintenance needs to be.
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Re: Top End Rebuild

Post by SS109 »

LOL! You guys make me seem crazy! I've got about 300 hours on my current 220 forged Wiseco piston and I ride my bike hard. It's finally due for replacement as the compression has dropped enough that I'm getting to the lower end of spec.

IMO/IME, with cast pistons it's about hours until replacement and forged it's about compression but that's just me.
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Re: Top End Rebuild

Post by KDXGarage »

I'll bite. You are losing performance. :-)

Get in there and at least change the rings. You can even clean the power valve system while you are at it. :-)
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Re: Top End Rebuild

Post by SS109 »

KDXGarage wrote: 07:56 pm Jan 15 2022 I'll bite. You are losing performance. :-)

Get in there and at least change the rings. You can even clean the power valve system while you are at it. :-)
Ha! No, bike still runs fantastic. It might have lost some power but I honestly couldn't tell you as it would have happened so gradually I wouldn't notice. Bike still pulls hard and lugs down low great. Only thing that's changed is it now takes three kicks to start cold instead of two. I do pull the pipe once in a while to take a look at things and everything looks great (skirt, cylinder, PV parts) other than a little blow by past the rings. I will be taking care of it soon.
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Re: Top End Rebuild

Post by KDXGarage »

Blow by equals past time for new rings to me.
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Re: Top End Rebuild

Post by SS109 »

KDXGarage wrote: 08:12 pm Jan 15 2022 Blow by equals past time for new rings to me.
I agree completely.

I admit, I had been neglecting my KDX as I have been collecting the parts to get my GasGas back together but no more.
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Re: Top End Rebuild

Post by KDXGarage »

You are not collecting parts for the Gas Gas?
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Re: Top End Rebuild

Post by SS109 »

KDXGarage wrote: 09:13 pm Jan 16 2022 You are not collecting parts for the Gas Gas?
I am but putting the Gasser on the back burner to take care of the KDX and some work I need to do to my truck.
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Re: Top End Rebuild

Post by KDXGarage »

Ah, OK. I thought it was down and going to be kept down. Good to hear.
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