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Old 02-20-2005, 02:49 AM
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Default what a bummer

     

I was just about to re-assemble my topend in my kx 250. I was going over some last minute checks and realized that the intake side of my piston was all scored up. This motor has gone through 2 years of riding without a fresh topend. I really don't know what happened to my piston. The rest of my piston is fine except for my intake side. Is this a trait of these motors or is it just my bad luck? Here is a pic of my piston. Can anyone tell me whether it is too badly scored to go another round? (It feels a little bumpy)
http://www.allthingsmoto.com/photopo...0_0661-med.JPG
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Old 02-20-2005, 07:28 AM
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Default Re: what a bummer

Quote:
Originally Posted by melenko
I was just about to re-assemble my topend in my kx 250. I was going over some last minute checks and realized that the intake side of my piston was all scored up. This motor has gone through 2 years of riding without a fresh topend. I really don't know what happened to my piston. The rest of my piston is fine except for my intake side. Is this a trait of these motors or is it just my bad luck? Here is a pic of my piston. Can anyone tell me whether it is too badly scored to go another round? (It feels a little bumpy)
http://www.allthingsmoto.com/photopo...0_0661-med.JPG

Pistons are cheap enough to just replace since you are already in there. Why risk doing the work twice?
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Old 02-20-2005, 07:46 PM
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mtk mtk is offline
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Default Re: what a bummer

Quote:
Originally Posted by melenko
This motor has gone through 2 years of riding without a fresh topend. I really don't know what happened to my piston.

The first sentence is the answer to the second. Pistons don't last forever. A quick perusal of my two CR250 shop manuals shows that Honda recommends a new piston and rings every 7.5 hours of use in racing conditions. I'd say you got your money's worth out of that one.
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Old 02-20-2005, 08:12 PM
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Default Re: what a bummer

Yeah, definately go for a new piston kit, and set a top end replacement limit for yourself so you won't get this again.

And btw, how long do you warm the bike up? I *think* that the intake side being scored means that the bike is being revved too much before the cylinder has heated up and expanded.
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Old 02-21-2005, 03:39 AM
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Default Re: what a bummer

*Usually* intake side scoring can indicate 2 things;

=> Loss of lubrication.
There are three possible causes for loss of lubrication, no pre-mix oil, separation of the fuel and pre-mix oil in the fuel tank, water passed through the air-filter and washed the oil film off the piston skirt.

=> Wear On Crank. Not as common as first but it can be a sign that your crank is worn.

Hope this helps.

Btw, check out the Eric Gorr site.

Particularly here
http://www.eric-gorr.com/twostktech/twostroketech.html
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